JUSTICE SCALIA, with whom JUSTICE THOMAS and JUSTICE ALITO join, dissenting.

On December 30, 2005, Congress enacted the Detainee Treatment Act (DTA). It unambiguously provides that, as of that date, "no court, justice, or judge" shall have jurisdiction to consider the habeas application of a Guantanamo Bay detainee. Notwithstanding this plain directive, the Court today concludes that, on what it calls the statute's most natural reading, every "court, justice, or judge" before whom such a habeas application was pending on December 30 has jurisdiction to hear, consider, and render judgment on it. This conclusion is patently erroneous. And even if it were not, the jurisdiction supposedly retained should, in an exercise of sound equitable discretion, not be exercised.

I A

The DTA provides: "[N]o court, justice, or judge shall have jurisdiction to hear or consider an application for a writ of habeas corpus filed by or on behalf of an alien detained by the Department of Defense at Guantanamo Bay, Cuba." § 1005(e)(1), 119 Stat. 2742 (internal division omitted). This provision "t[ook] effect on the date of the enactment of this Act," § 1005(h)(1), id., at 2743, which was December 30, 2005. As of that date, then, no court had jurisdiction to "hear or consider" the merits of petitioner's habeas application. This repeal of jurisdiction is simply not ambiguous as between pending and future cases. It prohibits any exercise of jurisdiction, and it became effective as to all cases last December 30. It is also perfectly clear that the phrase "no court, justice, or judge" includes this Court and its Members, and that by exercising our appellate jurisdiction in this case we are "hear[ing] or consider[ing] . . . an application for a writ of habeas corpus."

An ancient and unbroken line of authority attests that statutes ousting jurisdiction unambiguously apply to cases pending at their effective date. For example, in Bruner v. United States, 343 U. S. 112 (1952), we granted certiorari to consider whether the Tucker Act's provision denying district court jurisdiction over suits by "officers" of the United States barred a suit by an employee of the United States. After we granted certiorari, Congress amended the Tucker Act by adding suits by "`employees'" to the provision barring jurisdiction over suits by officers. Id., at 114. This statute narrowing the jurisdiction of the district courts "became effective" while the case was pending before us, ibid., and made no explicit reference to pending cases. Because the statute "did not reserve jurisdiction over pending cases," id., at 115, we held that it clearly ousted jurisdiction over them. Summarizing centuries of practice, we said: "This rule — that, when a law conferring jurisdiction is repealed without any reservation as to pending cases, all cases fall with the law — has been adhered to consistently by this Court." Id., at 116-117. See also Landgraf v. USI Film Products, 511 U. S. 244, 274 (1994) (opinion for the Court by STEVENS, J.) ("We have regularly applied intervening statutes conferring or ousting jurisdiction, whether or not jurisdiction lay when the underlying conduct occurred or when the suit was filed").

This venerable rule that statutes ousting jurisdiction terminate jurisdiction in pending cases is not, as today's opinion for the Court would have it, a judge-made "presumption against jurisdiction," ante, at 576, that we have invented to resolve an ambiguity in the statutes. It is simple recognition of the reality that the plain import of a statute repealing jurisdiction is to eliminate the power to consider and render judgment — in an already pending case no less than in a case yet to be filed.

"Without jurisdiction the court cannot proceed at all in any cause. Jurisdiction is power to declare the law, and when it ceases to exist, the only function remaining to the court is that of announcing the fact and dismissing the cause. And this is not less clear upon authority than upon principle." Ex parte McCardle, 7 Wall. 506, 514 (1869) (emphasis added).

To alter this plain meaning, our cases have required an explicit reservation of pending cases in the jurisdiction-repealing statute. For example, Bruner, as mentioned, looked to whether Congress made "any reservation as to pending cases." 343 U. S., at 116-117; see also id., at 115 ("Congress made no provision for cases pending at the effective date of the Act withdrawing jurisdiction and, for this reason, Courts of Appeals ordered pending cases terminated for want of jurisdiction"). Likewise, in Hallowell v. Commons, 239 U. S. 506 (1916), Justice Holmes relied on the fact that the jurisdiction-ousting provision "made no exception for pending litigation, but purported to be universal," id., at 508. And in Insurance Co. v. Ritchie, 5 Wall. 541 (1867), we again relied on the fact that the jurisdictional repeal was made "without any saving of such causes as that before us," id., at 544. As in Bruner, Hallowell, and Ritchie, the DTA's directive that "no court, justice, or judge shall have jurisdiction," § 1005(e)(1), 119 Stat. 2742, is made "without any reservation as to pending cases" and "purport[s] to be universal." What we stated in an earlier case remains true here: "[W]hen, if it had been the intention to confine the operation of [the jurisdictional repeal] . . . to cases not pending, it would have been so easy to have said so, we must presume that Congress meant the language employed should have its usual and ordinary signification, and that the old law should be unconditionally repealed." Railroad Co. v. Grant, 98 U. S. 398, 403 (1879).

The Court claims that I "rea[d] too much into" the Bruner line of cases, ante, at 577, n. 7, and that "the Bruner rule" has never been "an inflexible trump," ante, at 584. But the Court sorely misdescribes Bruner — as if it were a kind of early-day Lindh v. Murphy, 521 U. S. 320 (1997), resolving statutory ambiguity by oblique negative inference. On the contrary, as described above, Bruner stated its holding as an unqualified "rule," which "has been adhered to consistently by this Court." 343 U. S., at 116-117. Though Bruner referred to an express saving clause elsewhere in the statute, id., at 115, n. 7, it disavowed any reliance on such oblique indicators to vary the plain meaning, quoting Ritchie at length: "`It is quite possible that this effect of the [jurisdiction-stripping statute] was not contemplated by Congress. . . . [B]ut when terms are unambiguous we may not speculate on probabilities of intention."' 343 U. S., at 116 (quoting 5 Wall., at 544-545).

The Court also attempts to evade the Bruner line of cases by asserting that "the `presumption' [of application to pending eases] that these cases have applied is more accurately viewed as the nonapplication of another presumption — viz., the presumption against retroactivity — in certain limited circumstances." Ante, at 576. I have already explained that what the Court calls a "presumption" is simply the acknowledgment of the unambiguous meaning of such provisions. But even taking it to be what the Court says, the effect upon the present case would be the same. Prospective applications of a statute are "effective" upon the statute's effective date; that is what an effective date provision like § 1005(h)(1) means. "`[S]hall take effect upon enactment' is presumed to mean `shall have prospective effect upon enactment,' and that presumption is too strong to be overcome by any negative inference [drawn from other provisions of the statute]." Landgraf, supra, at 288 (SCALIA, J., concurring in judgments). The Court's "nonapplication of . . . the presumption against retroactivity" to § 1005(e)(1) is thus just another way of stating that the statute takes immediate effect in pending cases.

Though the Court resists the Bruner rule, it cannot cite a single case in the history of Anglo-American law (before today) in which a jurisdiction-stripping provision was denied immediate effect in pending cases, absent an explicit statutory reservation. By contrast, the cases granting such immediate effect are legion, and they repeatedly rely on the plain language of the jurisdictional repeal as an "inflexible trump," ante, at 584, by requiring an express reservation to save pending cases. See, e. g., Bruner, supra, at 115; Kline v. Burke Constr. Co., 260 U. S. 226, 234 (1922); Hallowell, 239 U.S., at 508; Gwin v. United States, 184 U. S. 669, 675 (1902); Gurnee v. Patrick County, 137 U. S. 141, 144 (1890); Sherman v. Grinnell, 123 U. S. 679, 680 (1887); Railroad Co. v. Grant, supra, at 403, Assessors v. Osbornes, 9 Wall. 567, 575 (1870); Ex parte McCardle, 7 Wall., at 514; Ritchie, supra, at 544; Norris v. Crocker, 13 How. 429, 440 (1852); Yeaton v. United States, 5 Cranch 281 (1809) (Marshall, C. J.), discussed in Gwin, supra, at 675; King v. Justices of the Peace of London, 3 Burr. 1456, 1457, 97 Eng. Rep. 924, 925 (K. B. 1764). Cf. National Exchange Bank of Baltimore v. Peters, 144 U. S. 570, 572 (1892).

B

Disregarding the plain meaning of § 1005(e)(1) and the requirement of explicit exception set forth in the foregoing cases, the Court instead favors "a negative inference . . . from the exclusion of language from one statutory provision that is included in other provisions of the same statute," ante, at 578. Specifically, it appeals to the fact that § 1005(e)(2) and (e)(3) are explicitly made applicable to pending cases (by § 1005(h)(2)). A negative inference of the sort the Court relies upon might clarify the meaning of an ambiguous provision, but since the meaning of § 1005(e)(1) is entirely clear, the omitted language in that context would have been redundant.

Even if § 1005(e)(1) were at all ambiguous in its application to pending cases, the "negative inference" from § 1005(h)(2) touted by the Court would have no force. The numerous cases in the Bruner line would at least create a powerful default "presumption against jurisdiction," ante, at 576. The negative inference urged by the Court would be a particularly awkward and indirect way of rebutting such a longstanding and consistent practice. This is especially true since the negative inference that might be drawn from § 1005(h)(2)'s specification that certain provisions shall apply to pending cases is matched by a negative inference in the opposite direction that might be drawn from § 1005(b)(2), which provides that certain provisions shall not apply to pending cases.

The Court's reliance on our opinion in Lindh v. Murphy, 521 U. S. 320 (1997), is utterly misplaced. Lindh involved two provisions of the Antiterrorism and Effective Death Penalty Act of 1996 (AEDPA): a set of amendments to chapter 153 of the federal habeas statute that redefined the scope of collateral review by federal habeas courts; and a provision creating a new chapter 154 in the habeas statute specially to govern federal collateral review of state capital cases. See 521 U. S., at 326-327. The latter provision explicitly rendered the new chapter 154 applicable to cases pending at the time of AEDPA's enactment; the former made no specific reference to pending cases. Id., at 327. In Lindh, we drew a negative inference from chapter 154's explicit reference to pending cases, to conclude that the chapter 153 amendments did not apply in pending cases. It was essential to our reasoning, however, that both provisions appeared to be identically difficult to classify under our retroactivity cases. First, we noted that, after Landgraf, there was reason for Congress to suppose that an explicit statement was required to render the amendments to chapter 154 applicable in pending cases, because the new chapter 154 "will have substantive as well as purely procedural effects." 521 U. S., at 327. The next step — and the critical step — in our reasoning was that Congress had identical reason to suppose that an explicit statement would be required to apply the chapter 153 amendments to pending eases, but did not provide it. Id., at 329. The negative inference of Lindh rested on the fact that "[n]othing . . . but a different intent explain[ed] the different treatment." Ibid.

Here, by contrast, there is ample reason for the different treatment. The exclusive-review provisions of the DTA, unlike both § 1005(e)(1) and the AEDPA amendments in Lindh, confer new jurisdiction (in the D. C. Circuit) where there was none before. For better or for worse, our recent cases have contrasted jurisdiction- creating provisions with jurisdiction- ousting provisions, retaining the venerable rule that the latter are not retroactive even when applied in pending cases, but strongly indicating that the former are typically retroactive. For example, we stated in Hughes Aircraft Co. v. United States ex rel. Schumer, 520 U. S. 939, 951 (1997), that a statute that " creates jurisdiction where none previously existed" is "as much subject to our presumption against retroactivity as any other." See also Republic of Austria v. Altmann, 541 U. S. 677, 695 (2004) (opinion for the Court by STEVENS, J.); id., at 722 (KENNEDY, J., dissenting). The Court gives our retroactivity jurisprudence a dazzling clarity in asserting that "subsections (e)(2) and (e)(3) `confer' jurisdiction in a manner that cannot conceivably give rise to retroactivity questions under our precedents." Ante, at 582. This statement rises to the level of sarcasm when one considers its author's description of the governing test of our retroactivity jurisprudence:

"The conclusion that a particular rule operates `retroactively' comes at the end of a process of judgment concerning the nature and extent of the change in the law and the degree of connection between the operation of the new rule and a relevant past event. Any test of retroactivity will leave room for disagreement in hard cases, and is unlikely to classify the enormous variety of legal changes with perfect philosophical clarity. However, retroactivity is a matter on which judges tend to have `sound . . . instinct[s],' . . . and familiar considerations of fair notice, reasonable reliance, and settled expectations offer sound guidance." Landgraf, 511 U. S., at 270 (opinion for the Court by STEVENS, J.).

The only "familiar consideration," "reasonable reliance," and "settled expectation" I am aware of pertaining to the present case is the rule of Bruner — applicable to § 1005(e)(1), but not to § 1005(e)(2) and (e)(3) — which the Court stubbornly disregards. It is utterly beyond question that § 1005(e)(2)'s and (3)'s application to pending cases (without explicit specification) was not as clear as § 1005(e)(1)'s. That is alone enough to explain the difference in treatment.

Another obvious reason for the specification was to stave off any Suspension Clause problems raised by the immediately effective ouster of jurisdiction brought about by subsection (e)(1). That is to say, specification of the immediate effectiveness of subsections (e)(2) and (e)(3) (which, unlike subsection (e)(1), would not fall within the Bruner rule and would not automatically be deemed applicable in pending cases) could reasonably have been thought essential to be sure of replacing the habeas jurisdiction that subsection (e)(1) eliminated in pending cases with an adequate substitute. See infra, at 670-672.

These considerations by no means prove that an explicit statement would be required to render subsections (e)(2) and (e)(3) applicable in pending cases. But they surely gave Congress ample reason to doubt that their application in pending cases would unfold as naturally as the Court glibly assumes. In any event, even if it were true that subsections (e)(2) and (e)(3) "`confer' jurisdiction in a manner that cannot conceivably give rise to retroactivity questions," ante, at 582, this would merely establish that subsection (h)(2)'s reference to pending cases was wholly superfluous when applied to subsections (e)(2) and (e)(3), just as it would have been for subsection (e)(1). Lindh's negative inference makes sense only when Congress would have perceived "the wisdom of being explicit" with respect to the immediate application of both of two statutory provisions, 521 U. S., at 328, but chose to be explicit only for one of them — not when it would have perceived no need to be explicit for both, but enacted a redundancy only for one.

In short, it is simply untrue that Congress "`should have been just as concerned about'" specifying the application of § 1005(e)(1) to pending cases, ante, at 578 (quoting Lindh, supra, at 329). In fact, the negative-inference approach of Lindh is particularly inappropriate in this case, because the negative inference from § 1005(h)(2) would tend to defeat the purpose of the very provisions that are explicitly rendered applicable in pending cases, § 1005(e)(2) and (3). Those provisions purport to vest "exclusive" jurisdiction in the D. C. Circuit to consider the claims raised by petitioner here. See infra, at 670-672. By drawing a negative inference a la Lindh, the Court supplants this exclusive-review mechanism with a dual-review mechanism for petitioners who were expeditious enough to file applications challenging the CSRTs or military commissions before December 30, 2005. Whatever the force of Lindh's negative inference in other cases, it surely should not apply here to defeat the purpose of the very provision from which the negative inference is drawn.

C

Worst of all is the Court's reliance on the legislative history of the DTA to buttress its implausible reading of § 1005(e)(1). We have repeatedly held that such reliance is impermissible where, as here, the statutory language is unambiguous. But the Court nevertheless relies both on floor statements from the Senate and (quite heavily) on the drafting history of the DTA. To begin with floor statements: The Court urges that some "statements made by Senators preceding passage of the Act lend further support to" the Court's interpretation, citing excerpts from the floor debate that support its view, ante, at 580, n. 10. The Court immediately goes on to discount numerous floor statements by the DTA's sponsors that flatly contradict its view, because "those statements appear to have been inserted into the Congressional Record, after the Senate debate." Ibid. Of course this observation, even if true, makes no difference unless one indulges the fantasy that Senate floor speeches are attended (like the Philippics of Demosthenes) by throngs of eager listeners, instead of being delivered (like Demosthenes' practice sessions on the beach) alone into a vast emptiness. Whether the floor statements are spoken where no Senator hears, or written where no Senator reads, they represent at most the views of a single Senator. In any event, the Court greatly exaggerates the one-sidedness of the portions of the floor debate that clearly occurred before the DTA's enactment. Some of the statements of Senator Graham, a sponsor of the bill, only make sense on the assumption that pending cases are covered. And at least one opponent of the DTA unmistakably expressed his understanding that it would terminate our jurisdiction in this very case. (Of course in its discussion of legislative history the Court wholly ignores the President's signing statement, which explicitly set forth his understanding that the DTA ousted jurisdiction over pending cases.)

But selectivity is not the greatest vice in the Court's use of floor statements to resolve today's case. These statements were made when Members of Congress were fully aware that our continuing jurisdiction over this very case was at issue. The question was divisive, and floor statements made on both sides were undoubtedly opportunistic and crafted solely for use in the briefs in this very litigation. See, e. g., 151 Cong. Rec. S14257-S14258 (Dec. 21, 2005) (statement of Sen. Levin) (arguing against a reading that would "stri[p] the Federal courts of jurisdiction to consider pending cases, including the Harridan case now pending in the Supreme Court," and urging that Lindh requires the same negative inference that the Court indulges today (emphasis added)). The Court's reliance on such statements cannot avoid the appearance of similar opportunism. In a virtually identical context, the author of today's opinion has written for the Court that "[t]he legislative history discloses some frankly partisan statements about the meaning of the final effective date language, but those statements cannot plausibly be read as reflecting any general agreement." Landgraf, 511 U. S., at 262 (opinion for the Court by STEVENS, J.). Likewise, the handful of floor statements that the Court treats as authoritative do not "reflec[t] any general agreement." They reflect the now-common tactic — which the Court once again rewards — of pursuing through floor-speech ipse dixit what could not be achieved through the constitutionally prescribed method of putting language into a bill that a majority of both Houses vote for and the President signs.

With regard to the floor statements, at least the Court shows some semblance of seemly shame, tucking away its reference to them in a halfhearted footnote. Not so for its reliance on the DTA's drafting history, which is displayed prominently, see ante, at 579-580. I have explained elsewhere that such drafting history is no more legitimate or reliable an indicator of the objective meaning of a statute than any other form of legislative history. This case presents a textbook example of its unreliability. The Court, ante, at 579, trumpets the fact that a bill considered in the Senate included redundant language, not included in the DTA as passed, reconfirming that the abolition of habeas jurisdiction "shall apply to any application or other action that is pending on or after the date of the enactment of this Act." 151 Cong. Rec. S12655 (Nov. 10, 2005). But this earlier version of the bill also differed from the DTA in other material respects. Most notably, it provided for postdecision review by the D. C. Circuit only of the decisions of CSRTs, not military commissions, ibid.; and it limited that review to whether "the status determination . . . was consistent with the procedures and standards specified by the Secretary of Defense," ibid., not whether "the use of such standards and procedures . . . is consistent with the Constitution and laws of the United States," DTA § 1005(e)(2)(C)(ii), 119 Stat. 2742. To say that what moved Senators to reject this earlier bill was the "action that is pending" provision surpasses the intuitive powers of even this Court's greatest Justices. And to think that the House and the President also had this rejection firmly in mind is absurd. As always — but especially in the context of strident, partisan legislative conflict of the sort that characterized enactment of this legislation — the language of the statute that was actually passed by both Houses of Congress and signed by the President is our only authoritative and only reliable guidepost.

D

A final but powerful indication of the fact that the Court has made a mess of this statute is the nature of the consequences that ensue. Though this case concerns a habeas application challenging a trial by military commission, DTA § 1005(e)(1) strips the courts of jurisdiction to hear or consider any "application for a writ of habeas corpus filed by or on behalf of an alien detained by the Department of Defense at Guantanamo Bay, Cuba." The vast majority of pending petitions, no doubt, do not relate to military commissions at all, but to more commonly challenged aspects of "detention" such as the terms and conditions of confinement. See Rasul v. Bush, 542 U. S. 466, 498 (2004) (SCALIA, J., dissenting). The Solicitor General represents that "[h]abeas petitions have been filed on behalf of a purported 600 [Guantanamo Bay] detainees," including one that "seek[s] relief on behalf of every Guantanamo detainee who has not already filed an action," Respondents' Motion to Dismiss for Lack of Jurisdiction 20, n. 10 (hereinafter Motion to Dismiss). The Court's interpretation transforms a provision abolishing jurisdiction over all Guantanamo-related habeas petitions into a provision that retains jurisdiction over cases sufficiently numerous to keep the courts busy for years to come.

II

Because I would hold that § 1005(e)(1) unambiguously terminates the jurisdiction of all courts to "hear or consider" pending habeas applications, I must confront petitioner's arguments that the provision, so interpreted, violates the Suspension Clause. This claim is easily dispatched. We stated in Johnson v. Eisentrager, 339 U. S. 763, 768 (1950):

"We are cited to no instance where a court, in this or any other country where the writ is known, has issued it on behalf of an alien enemy who, at no relevant time and in no stage of his captivity, has been within its territorial jurisdiction. Nothing in the text of the Constitution extends such a right, nor does anything in our statutes."

Notwithstanding the ill-considered dicta in the Court's opinion in Rasul, 542 U. S., at 480-481, it is clear that Guantanamo Bay, Cuba, is outside the sovereign "territorial jurisdiction" of the United States. See id., at 500-505 (SCALIA, J., dissenting). Petitioner, an enemy alien detained abroad, has no rights under the Suspension Clause.

But even if petitioner were fully protected by the Clause, the DTA would create no suspension problem. This Court has repeatedly acknowledged that "the substitution of a collateral remedy which is neither inadequate nor ineffective to test the legality of a person's detention does not constitute a suspension of the writ of habeas corpus." Swain v. Pressley, 430 U. S. 372, 381 (1977); see also INS v. St. Cyr, 533 U. S. 289, 314, n. 38 (2001) ("Congress could, without raising any constitutional questions, provide an adequate substitute through the courts of appeals").

Petitioner has made no showing that the postdecision exclusive review by the D. C. Circuit provided in § 1005(e)(3) is inadequate to test the legality of his trial by military commission. His principal argument is that the exclusive-review provisions are inadequate because they foreclose review of the claims he raises here. Though petitioner's brief does not parse the statutory language, his argument evidently rests on an erroneously narrow reading of DTA § 1005(e)(3)(D)(ii), 119 Stat. 2743. That provision grants the D. C. Circuit authority to review, "to the extent the Constitution and laws of the United States are applicable, whether the use of such standards and procedures to reach the final decision is consistent with the Constitution and laws of the United States." In the quoted text, the phrase "such standards and procedures" refers to "the standards and procedures specified in the military order referred to in subparagraph (A)," namely, "Military Commission Order No. 1, dated August 31, 2005 (or any successor military order)." DTA § 1005(e)(3)(D)(i), (e)(3)(A), ibid. This Military Commission Order (Order No. 1) is the Department of Defense's fundamental implementing order for the President's order authorizing trials by military commission. Order No. 1 establishes commissions, § 2; delineates their jurisdiction, § 3; provides for their officers, § 4(A); provides for their prosecution and defense counsel, § 4(B), (C); lays out all their procedures, both pretrial and trial, § 5(A)-(P), § 6(A)-(G); and provides for post-trial military review through the Secretary of Defense and the President, § 6(H). In short, the "standards and procedures specified in" Order No. 1 include every aspect of the military commissions, including the fact of their existence and every respect in which they differ from courts-martial. Petitioner's claims that the President lacks legal authority to try him before a military commission constitute claims that "the use of such standards and procedures," as specified in Order No. 1, is "[in]consistent with the Constitution and laws of the United States," DTA § 1005(e)(3)(D)(ii), 119 Stat. 2743. The D. C. Circuit thus retains jurisdiction to consider these claims on postdecision review, and the Government does not dispute that the DTA leaves unaffected our certiorari jurisdiction under 28 U.S.C. § 1254(1) to review the D. C. Circuit's decisions. Motion to Dismiss 16, n. 8. Thus, the DTA merely defers our jurisdiction to consider petitioner's claims; it does not eliminate that jurisdiction. It constitutes neither an "inadequate" nor an "ineffective" substitute for petitioner's pending habeas application.

Though it does not squarely address the issue, the Court hints ominously that "the Government's preferred reading" would "rais[e] grave questions about Congress' authority to impinge upon this Court's appellate jurisdiction, particularly in habeas cases." Ante, at 575 (citing Ex parte Yerger, 8 Wall. 85 (1869); Felker v. Turpin, 518 U. S. 651 (1996); Durousseau v. United States, 6 Cranch 307 (1810); United States v. Klein, 13 Wall. 128 (1872); and Ex parte McCardle, 7 Wall. 506). It is not clear how there could be any such lurking questions, in light of the aptly named " Exceptions Clause" of Article III, § 2, which, in making our appellate jurisdiction subject to "such Exceptions, and under such Regulations as the Congress shall make," explicitly permits exactly what Congress has done here. But any doubt our prior cases might have created on this score is surely chimerical in this case. As just noted, the exclusive-review provisions provide a substitute for habeas review adequate to satisfy the Suspension Clause, which forbids the suspension of the writ of habeas corpus. A fortiori they provide a substitute adequate to satisfy any implied substantive limitations, whether real or imaginary, upon the Exceptions Clause, which authorizes such exceptions as § 1005(e)(1).

III

Even if Congress had not clearly and constitutionally eliminated jurisdiction over this case, neither this Court nor the lower courts ought to exercise it. Traditionally, equitable principles govern both the exercise of habeas jurisdiction and the granting of the injunctive relief sought by petitioner. See Schlesinger v. Councilman, 420 U. S. 738, 754 (1975); Weinberger v. Romero-Barcelo, 456 U. S. 305, 311 (1982). In light of Congress's provision of an alternate avenue for petitioner's claims in § 1005(e)(3), those equitable principles counsel that we abstain from exercising jurisdiction in this case.

In requesting abstention, the Government relies principally on Councilman, in which we abstained from considering a serviceman's claim that his charge for marijuana possession was not sufficiently "service-connected" to trigger the subject-matter jurisdiction of the military courts-martial. See 420 U.S., at 740, 758. Admittedly, Councilman does not squarely control petitioner's case, but it provides the closest analogue in our jurisprudence. As the Court describes, ante, at 586, Councilman "identifie[d] two considerations of comity that together favor[ed] abstention pending completion of ongoing court-martial proceedings against service personnel." But the Court errs in finding these considerations inapplicable to this case. Both of them, and a third consideration not emphasized in Councilman, all cut in favor of abstention here.

First, the Court observes that Councilman rested in part on the fact that "military discipline and, therefore, the efficient operation of the Armed Forces are best served if the military justice system acts without regular interference from civilian courts," and concludes that "Hamdan is not a member of our Nation's Armed Forces, so concerns about military discipline do not apply." Ante, at 586, 587. This is true enough. But for some reason, the Court fails to make any inquiry into whether military commission trials might involve other "military necessities" or "unique military exigencies," 420 U. S., at 757, comparable in gravity to those at stake in Councilman. To put this in context: The charge against the respondent in Councilman was the off-base possession and sale of marijuana while he was stationed in Fort Sill, Oklahoma, see id., at 739-740. The charge against the petitioner here is joining and actively abetting the murderous conspiracy that slaughtered thousands of innocent American civilians without warning on September 11, 2001. While Councilman held that the prosecution of the former charge involved "military necessities" counseling against our interference, the Court does not even ponder the same question for the latter charge.

The reason for the Court's "blinkered study" of this question, ante, at 584, is not hard to fathom. The principal opinion on the merits makes clear that it does not believe that the trials by military commission involve any "military necessity" at all: "The charge's shortcomings . . . are indicative of a broader inability on the Executive's part here to satisfy the most basic precondition . . . for establishment of military commissions: military necessity." Ante, at 612. This is quite at odds with the views on this subject expressed by our political branches. Because of "military necessity," a joint session of Congress authorized the President to "use all necessary and appropriate force," including military commissions, "against those nations, organizations, or persons [such as petitioner] he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001." Authorization for Use of Military Force, § 2(a), 115 Stat. 224, note following 50 U.S.C. § 1541 (2000 ed., Supp. III). In keeping with this authority, the President has determined that "[t]o protect the United States and its citizens, and for the effective conduct of military operations and prevention of terrorist attacks, it is necessary for individuals subject to this order . . . to be detained, and, when tried, to be tried for violations of the laws of war and other applicable laws by military tribunals." Military Order of Nov. 13, 2001, 3 CFR, 2001 Comp., § 1(e), p. 918 (2002) (hereinafter Military Order). It is not clear where the Court derives the authority — or the audacity — to contradict this determination. If "military necessities" relating to "duty" and "discipline" required abstention in Councilman, supra, at 757, military necessities relating to the disabling, deterrence, and punishment of the mass-murdering terrorists of September 11 require abstention all the more here.

The Court further seeks to distinguish Councilman on the ground that "the tribunal convened to try Hamdan is not part of the integrated system of military courts, complete with independent review panels, that Congress has established." Ante, at 587. To be sure, Councilman emphasized that "Congress created an integrated system of military courts and review procedures, a critical element of which is the Court of Military Appeals consisting of civilian judges completely removed from all military influence or persuasion, who would gain over time thorough familiarity with military problems." 420 U. S., at 758 (internal quotation marks and footnote omitted). The Court contrasts this "integrated system" insulated from military influence with the review scheme established by Order No. 1, which "provides that appeal of a review panel's decision may be had only to the Secretary himself, § 6(H)(5), and then, finally, to the President, § 6(H)(6)." Ante, at 587.

Even if we were to accept the Court's extraordinary assumption that the President "lack[s] the structural insulation from military influence that characterizes the Court of Appeals for the Armed Forces," ante, at 587-588, the Court's description of the review scheme here is anachronistic. As of December 30, 2005, the "fina[l]" review of decisions by military commissions is now conducted by the D. C. Circuit pursuant to § 1005(e)(3) of the DTA, and by this Court under 28 U.S.C. § 1254(1). This provision for review by Article III courts creates, if anything, a review scheme more insulated from executive control than that in Councilman. At the time we decided Councilman, Congress had not "conferred on any Art[icle] III court jurisdiction directly to review court-martial determinations." 420 U. S., at 746. The final arbiter of direct appeals was the Court of Military Appeals (now the Court of Appeals for the Armed Forces), an Article I court whose members possessed neither life tenure, nor salary protection, nor the constitutional protection from removal provided to federal judges in Article III, § 1. See 10 U.S.C. § 867(a)(2) (1970 ed.).

Moreover, a third consideration counsels strongly in favor of abstention in this case. Councilman reasoned that the "considerations of comity, the necessity of respect for coordinate judicial systems" that motivated our decision in Younger v. Harris, 401 U. S. 37 (1971), were inapplicable to courts-martial, because "the peculiar demands of federalism are not implicated." 420 U. S., at 756, 757. Though military commissions likewise do not implicate "the peculiar demands of federalism," considerations of interbranch comity at the federal level weigh heavily against our exercise of equity jurisdiction in this case. Here, apparently for the first time in history, see Motion to Dismiss 6, a District Court enjoined ongoing military commission proceedings, which had been deemed "necessary" by the President "[t]o protect the United States and its citizens, and for the effective conduct of military operations and prevention of terrorist attacks." Military Order § 1(e). Such an order brings the Judicial Branch into direct conflict with the Executive in an area where the Executive's competence is maximal and ours is virtually nonexistent. We should exercise our equitable discretion to avoid such conflict. Instead, the Court rushes headlong to meet it. Elsewhere, we have deferred exercising habeas jurisdiction until state courts have "the first opportunity to review" a petitioner's claim, merely to "reduc[e] friction between the state and federal court systems." O'Sullivan v. Boerckel, 526 U. S. 838, 844, 845 (1999). The "friction" created today between this Court and the Executive Branch is many times more serious.

In the face of such concerns, the Court relies heavily on Ex parte Quirin, 317 U. S. 1 (1942): "Far from abstaining pending the conclusion of military proceedings, which were ongoing, [in Quirin] we convened a special Term to hear the case and expedited our review." Ante, at 588. It is likely that the Government in Quirin, unlike here, preferred a hasty resolution of the case in this Court, so that it could swiftly execute the sentences imposed, see Hamdi v. Rumsfeld, 542 U. S. 507, 569 (2004) (SCALIA, J., dissenting). But the Court's reliance on Quirin suffers from a more fundamental defect: Once again, it ignores the DTA, which creates an avenue for the consideration of petitioner's claims that did not exist at the time of Quirin. Collateral application for habeas review was the only vehicle available. And there was no compelling reason to postpone consideration of the Quirin application until the termination of military proceedings, because the only cognizable claims presented were general challenges to the authority of the commissions that would not be affected by the specific proceedings. See supra, at 662-663, n. 2. In the DTA, by contrast, Congress has expanded the scope of Article III review and has channeled it exclusively through a single, postverdict appeal to Article III courts. Because Congress has created a novel unitary scheme of Article III review of military commissions that was absent in 1942, Quirin is no longer governing precedent.

I would abstain from exercising our equity jurisdiction, as the Government requests.

* * *

For the foregoing reasons, I dissent.

JUSTICE THOMAS, with whom JUSTICE SCALIA joins, and with whom JUSTICE ALITO joins in all but Parts I, II-C-1, and III-B-2, dissenting.

For the reasons set forth in JUSTICE SCALIA'S dissent, it is clear that this Court lacks jurisdiction to entertain petitioner's claims, see ante, at 655-669. The Court having concluded otherwise, it is appropriate to respond to the Court's resolution of the merits of petitioner's claims because its opinion openly flouts our well-established duty to respect the Executive's judgment in matters of military operations and foreign affairs. The plurality's evident belief that it is qualified to pass on the "military necessity," ante, at 612, of the Commander in Chief's decision to employ a particular form of force against our enemies is so antithetical to our constitutional structure that it simply cannot go unanswered. I respectfully dissent.

I

Our review of petitioner's claims arises in the context of the President's wartime exercise of his Commander in Chief authority in conjunction with the complete support of Congress. Accordingly, it is important to take measure of the respective roles the Constitution assigns to the three branches of our Government in the conduct of war.

As I explained in Hamdi v. Rumsfeld, 542 U. S. 507 (2004), the structural advantages attendant to the Executive Branch — namely, the decisiveness, "`activity, secrecy, and dispatch'" that flow from the Executive's `"unity,"' id., at 581 (dissenting opinion) (quoting The Federalist No. 70, p. 472 (J. Cooke ed. 1961) (A. Hamilton)) — led the Founders to conclude that the "President ha[s] primary responsibility — along with the necessary power — to protect the national security and to conduct the Nation's foreign relations." 542 U. S., at 580. Consistent with this conclusion, the Constitution vests in the President "[t]he executive Power," Art. II, § 1, provides that he "shall be Commander in Chief" of the Armed Forces, § 2, and places in him the power to recognize foreign governments, § 3. This Court has observed that these provisions confer upon the President broad constitutional authority to protect the Nation's security in the manner he deems fit. See, e. g., Prize Cases, 2 Black 635, 668 (1863) ("If a war be made by invasion of a foreign nation, the President is not only authorized but bound to resist force by force . . . without waiting for any special legislative authority"); Fleming v. Page, 9 How. 603, 615 (1850) (acknowledging that the President has the authority to "employ [the Nation's Armed Forces] in the manner he may deem most effectual to harass and conquer and subdue the enemy").

Congress, to be sure, has a substantial and essential role in both foreign affairs and national security. But "Congress cannot anticipate and legislate with regard to every possible action the President may find it necessary to take or every possible situation in which he might act," and "[s]uch failure of Congress . . . does not, `especially . . . in the areas of foreign policy and national security,' imply `congressional disapproval' of action taken by the Executive." Dames Moore v. Regan, 453 U. S. 654, 678 (1981) (quoting Haig v. Agee, 453 U. S. 280, 291 (1981)). Rather, in these domains, the fact that Congress has provided the President with broad authorities does not imply — and the Judicial Branch should not infer — that Congress intended to deprive him of particular powers not specifically enumerated. See Dames Moore, 453 U. S., at 678 ("[T]he enactment of legislation closely related to the question of the President's authority in a particular case which evinces legislative intent to accord the President broad discretion may be considered to invite measures on independent presidential responsibility" (internal quotation marks omitted)).

When "the President acts pursuant to an express or implied authorization from Congress," his actions are "`supported by the strongest of presumptions and the widest latitude of judicial interpretation, and the burden of persuasion . . . rest[s] heavily upon any who might attack it.'" Id., at 668 (quoting Youngstown Sheet Tube Co. v. Sawyer, 343 U. S. 579, 637 (1952) (Jackson, J., concurring)). Accordingly, in the very context that we address today, this Court has concluded that "the detention and trial of petitioners — ordered by the President in the declared exercise of his powers as Commander in Chief of the Army in time of war and of grave public danger — are not to be set aside by the courts without the clear conviction that they are in conflict with the Constitution or laws of Congress constitutionally enacted." Ex parte Quirin, 317 U. S. 1, 25 (1942).

Under this framework, the President's decision to try Hamdan before a military commission for his involvement with al Qaeda is entitled to a heavy measure of deference. In the present conflict, Congress has authorized the President "to use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001 . . . in order to prevent any future acts of international terrorism against the United States by such nations, organizations or persons." Authorization for Use of Military Force (AUMF), 115 Stat. 224, note following 50 U.S.C. § 1541 (2000 ed., Supp. III) (emphasis added). As a plurality of the Court observed in Hamdi, the "capture, detention, and trial of unlawful combatants, by `universal agreement and practice,' are `important incident[s] of war,'" 542 U. S., at 518 (quoting Quirin, supra, at 28, 30; emphasis added), and are therefore "an exercise of the `necessary and appropriate force' Congress has authorized the President to use," Hamdi, 542 U. S., at 518; id., at 587 (THOMAS, J., dissenting). Hamdi's observation that military commissions are included within the AUMF's authorization is supported by this Court's previous recognition that "[a]n important incident to the conduct of war is the adoption of measures by the military commander, not only to repel and defeat the enemy, but to seize and subject to disciplinary measures those enemies who, in their attempt to thwart or impede our military effort, have violated the law of war." In re Yamashita, 327 U. S. 1, 11 (1946); see also Quirin, supra, at 28-29; Madsen v. Kinsella, 343 U. S. 341, 354, n. 20 (1952) ("`[T]he military commission . . . is an institution of the greatest importance in a period of war and should be preserved'" (quoting S. Rep. No. 229, 63d Cong., 2d Sess., 53 (1914) (testimony of Gen. Crowder))).

Although the Court concedes the legitimacy of the President's use of military commissions in certain circumstances, ante, at 594, it suggests that the AUMF has no bearing on the scope of the President's power to utilize military commissions in the present conflict, ibid. Instead, the Court determines the scope of this power based exclusively on Article 21 of the Uniform Code of Military Justice (UCMJ), 10 U.S.C. § 821, the successor to Article 15 of the Articles of War, which Quirin held "authorized trial of offenses against the law of war before [military] commissions." 317 U. S., at 29. As I shall discuss below, Article 21 alone supports the use of commissions here. Nothing in the language of Article 21, however, suggests that it outlines the entire reach of congressional authorization of military commissions in all conflicts — quite the contrary, the language of Article 21 pre-supposes the existence of military commissions under an independent basis of authorization. Indeed, consistent with Hamdi's conclusion that the AUMF itself authorizes the trial of unlawful combatants, the original sanction for military commissions historically derived from congressional authorization of "the initiation of war" with its attendant authorization of "the employment of all necessary and proper agencies for its due prosecution." W. Winthrop, Military Law and Precedents 831 (rev. 2d ed. 1920) (hereinafter Winthrop) (emphasis deleted). Accordingly, congressional authorization for military commissions pertaining to the instant conflict derives not only from Article 21 of the UCMJ, but also from the more recent, and broader, authorization contained in the AUMF.

I note the Court's error respecting the AUMF not because it is necessary to my resolution of this case — Hamdan's military commission can plainly be sustained solely under Article 21 — but to emphasize the complete congressional sanction of the President's exercise of his Commander in Chief authority to conduct the present war. In such circumstances, as previously noted, our duty to defer to the Executive's military and foreign policy judgment is at its zenith; it does not countenance the kind of second-guessing the Court repeatedly engages in today. Military and foreign policy judgments

"`are and should be undertaken only by those directly responsible to the people whose welfare they advance or imperil. They are decisions of a kind for which the Judiciary has neither aptitude, facilities nor responsibility and which has long been held to belong in the domain of political power not subject to judicial intrusion or inquiry.'" Hamdi, supra, at 582-583 (THOMAS, J., dissenting) (quoting Chicago Southern Air Lines, Inc. v. Waterman S. S. Corp., 333 U. S. 103, 111 (1948)).

It is within this framework that the lawfulness of Hamdan's commission should be examined.

II

The plurality accurately describes some aspects of the history of military commissions and the prerequisites for their use. Thus, I do not dispute that military commissions have historically been "used in three [different] situations," ante, at 595, and that the only situation relevant to the instant case is the use of military commissions "`to seize and subject to disciplinary measures those enemies who . . . have violated the law of war,'" ante, at 596 (quoting Quirin, supra, at 28-29). Similarly, I agree with the plurality that Winthrop's treatise sets forth the four relevant considerations for determining the scope of a military commission's jurisdiction, considerations relating to the (1) time and (2) place of the offense, (3) the status of the offender, and (4) the nature of the offense charged. Winthrop 836-840. The Executive has easily satisfied these considerations here. The plurality's contrary conclusion rests upon an incomplete accounting and an unfaithful application of those considerations.

A

The first two considerations are that a law-of-war military commission may only assume jurisdiction of "offences committed within the field of the command of the convening commander," and that such offenses "must have been committed within the period of the war." See id., at 836, 837; ante, at 597. Here, as evidenced by Hamdan's charging document, the Executive has determined that the theater of the present conflict includes "Afghanistan, Pakistan and other countries" where al Qaeda has established training camps, App. to Pet. for Cert. 64a, and that the duration of that conflict dates back (at least) to Usama bin Laden's August 1996 Declaration of Jihad Against the Americans, ibid. Under the Executive's description of the conflict, then, every aspect of the charge, which alleges overt acts in "Afghanistan, Pakistan, Yemen and other countries" taking place from 1996 to 2001, satisfies the temporal and geographic prerequisites for the exercise of law-of-war military commission jurisdiction. Id., at 65a-67a. And these judgments pertaining to the scope of the theater and duration of the present conflict are committed solely to the President in the exercise of his Commander in Chief authority. See Prize Cases, 2 Black, at 670 (concluding that the President's Commander in Chief judgment about the nature of a particular conflict was "a question to be decided by him, and this Court must be governed by the decisions and acts of the political department of the Government to which this power was entrusted").

Nevertheless, the plurality concludes that the legality of the charge against Hamdan is doubtful because "Hamdan is charged not with an overt act for which he was caught red-handed in a theater of war . . . but with an agreement the inception of which long predated . . . the [relevant armed conflict]." Ante, at 612 (emphasis in original). The plurality's willingness to second-guess the Executive's judgments in this context, based upon little more than its unsupported assertions, constitutes an unprecedented departure from the traditionally limited role of the courts with respect to war and an unwarranted intrusion on executive authority. And even if such second-guessing were appropriate, the plurality's attempt to do so is unpersuasive.

As an initial matter, the plurality relies upon the date of the AUMF's enactment to determine the beginning point for the "period of the war," Winthrop 836-837, thereby suggesting that petitioner's commission does not have jurisdiction to try him for offenses committed prior to the AUMF's enactment. Ante, at 598-600, 612. But this suggestion betrays the plurality's unfamiliarity with the realities of warfare and its willful blindness to our precedents. The starting point of the present conflict (or indeed any conflict) is not determined by congressional enactment, but rather by the initiation of hostilities. See Prize Cases, supra, at 668 (recognizing that war may be initiated by "invasion of a foreign nation," and that such initiation, and the President's response, usually precedes congressional action). Thus, Congress' enactment of the AUMF did not mark the beginning of this Nation's conflict with al Qaeda, but instead authorized the President to use force in the midst of an ongoing conflict. Moreover, while the President's "war powers" may not have been activated until the AUMF was passed, ante, at 599, n. 31 (emphasis deleted), the date of such activation has never been used to determine the scope of a military commission's jurisdiction. Instead, the traditional rule is that "[o]ffenses committed before a formal declaration of war or before the declaration of martial law may be tried by military commission." Green, The Military Commission, 42 Am. J. Int'l L. 832, 848 (1948) (hereinafter Green); see also C. Howland, Digest of Opinions of the Judge-Advocates General of the Army 1067 (1912) (hereinafter Howland) ("A military commission . . . exercising . . . jurisdiction . . . under the laws of war . . . may take cognizance of offenses committed, during the war, before the initiation of the military government or martial law" (emphasis in original)); cf. Yamashita, 327 U. S., at 13 ("The extent to which the power to prosecute violations of the law of war shall be exercised before peace is declared rests, not with the courts, but with the political branch of the Government"). Consistent with this principle, on facts virtually identical to those here, a military commission tried Julius Otto Kuehn for conspiring with Japanese officials to betray the United States Fleet to the Imperial Japanese Government prior to its attack on Pearl Harbor. Green 848.

Moreover, the President's determination that the present conflict dates at least to 1996 is supported by overwhelming evidence. According to the State Department, al Qaeda declared war on the United States as early as August 1996. See Dept. of State Fact Sheet: Usama bin Ladin (Aug. 21, 1998); Dept. of State Fact Sheet: The Charges against International Terrorist Usama Bin Laden (Dec. 20, 2000); cf. Prize Cases, 2 Black, at 668 (recognizing that a state of war exists even if "the declaration of it be unilateral" (emphasis in original)). In February 1998, al Qaeda leadership issued another statement ordering the indiscriminate — and, even under the laws of war as applied to legitimate nation-states, plainly illegal — killing of American civilians and military personnel alike. See Jihad Against Jews and Crusaders: World Islamic Front Statement 2 (Feb. 23, 1998), in Y. Alexander M. Swetnam, Usama bin Laden's al-Qaida: Profile of a Terrorist Network, App. 1B (2001) ("The ruling to kill the Americans and their allies — civilians and military — is an individual duty for every Muslim who can do it in any country in which it is possible to do it"). This was not mere rhetoric; even before September 11, 2001, al Qaeda was involved in the bombing of the World Trade Center in New York City in 1993, the bombing of the Khobar Towers in Saudi Arabia in 1996, the bombing of the U. S. Embassies in Kenya and Tanzania in 1998, and the attack on the U. S. S. Cole in Yemen in 2000. See id., at 1. In response to these incidents, the United States "attack[ed] facilities belonging to Usama bin Ladin's network" as early as 1998. Dept. of State Fact Sheet: Usama bin Ladin (Aug. 21, 1998). Based on the foregoing, the President's judgment — that the present conflict substantially predates the AUMF, extending at least as far back as al Qaeda's 1996 declaration of war on our Nation, and that the theater of war extends at least as far as the localities of al Qaeda's principal bases of operations — is beyond judicial reproach. And the plurality's unsupportable contrary determination merely confirms that "`the Judiciary has neither aptitude, facilities nor responsibility'" for making military or foreign affairs judgments. Hamdi, 542 U. S., at 585 (THOMAS, J., dissenting) (quoting Chicago Southern Air Lines, 333 U. S., at 111).

B

The third consideration identified by Winthrop's treatise for the exercise of military commission jurisdiction pertains to the persons triable before such a commission, see ante, at 597-598; Winthrop 838. Law-of-war military commissions have jurisdiction over "`[i]ndividuals of the enemy's army who have been guilty of illegitimate warfare or other offences in violation of the laws of war,'" ante, at 598 (quoting Winthrop 838). They also have jurisdiction over "[i]rregular armed bodies or persons not forming part of the organized forces of a belligerent" "who would not be likely to respect the laws of war." Id., at 783, 784. Indeed, according to Winthrop, such persons are not "within the protection of the laws of war" and were "liable to be shot, imprisoned, or banished, either summarily where their guilt was clear or upon trial and conviction by military commission." Id., at 784. This consideration is easily satisfied here, as Hamdan is an unlawful combatant charged with joining and conspiring with a terrorist network dedicated to flouting the laws of war. 344 F. Supp. 2d 152, 161 (DC 2004); App. to Pet. for Cert. 63a-67a.

C

The fourth consideration relevant to the jurisdiction of law-of-war military commissions relates to the nature of the offense charged. As relevant here, such commissions have jurisdiction to try "`[v]iolations of the laws and usages of war cognizable by military tribunals only,'" ante, at 598 (quoting Winthrop 839). In contrast to the preceding considerations, this Court's precedents establish that judicial review of "whether any of the acts charged is an offense against the law of war cognizable before a military tribunal" is appropriate. Quirin, 317 U. S., at 29. However, "charges of violations of the law of war triable before a military tribunal need not be stated with the precision of a common law indictment." Yamashita, 327 U. S., at 17. And whether an offense is a violation of the law of war cognizable before a military commission must be determined pursuant to "the system of common law applied by military tribunals." Quirin, supra, at 30; Yamashita, supra, at 8.

The common law of war as it pertains to offenses triable by military commission is derived from the "experience of our wars" and our wartime tribunals, Winthrop 839, and "the laws and usages of war as understood and practiced by the civilized nations of the world," 11 Op. Atty. Gen. 297, 310 (1865). Moreover, the common law of war is marked by two important features. First, as with the common law generally, it is flexible and evolutionary in nature, building upon the experience of the past and taking account of the exigencies of the present. Thus, "[t]he law of war, like every other code of laws, declares what shall not be done, and does not say what may be done. The legitimate use of the great power of war, or rather the prohibitions upon the use of that power, increase or diminish as the necessity of the case demands." Id., at 300. Accordingly, this Court has recognized that the "jurisdiction" of "our common-law war courts" has not been "prescribed by statute," but rather "has been adapted in each instance to the need that called it forth." Madsen, 343 U. S., at 346-348. Second, the common law of war affords a measure of respect for the judgment of military commanders. Thus, "[t]he commander of an army in time of war has the same power to organize military tribunals and execute their judgments that he has to set his squadrons in the field and fight battles. His authority in each case is from the law and usage of war." 11 Op. Atty. Gen., at 305. In recognition of these principles, Congress has generally "`left it to the President, and the military commanders representing him, to employ the commission, as occasion may require, for the investigation and punishment of violations of the laws of war.'" Madsen, supra, at 347, n. 9 (quoting Winthrop 831; emphasis added).

In one key respect, the plurality departs from the proper framework for evaluating the adequacy of the charge against Hamdan under the laws of war. The plurality holds that where, as here, "neither the elements of the offense nor the range of permissible punishments is defined by statute or treaty, the precedent [establishing whether an offense is triable by military commission] must be plain and unambiguous." Ante, at 602. This is a pure contrivance, and a bad one at that. It is contrary to the presumption we acknowledged in Quirin, namely, that the actions of military commissions are "not to be set aside by the courts without the clear conviction that they are" unlawful, 317 U. S., at 25 (emphasis added). It is also contrary to Yamashita, which recognized the legitimacy of that military commission notwithstanding a substantial disagreement pertaining to whether Yamashita had been charged with a violation of the law of war. Compare 327 U. S., at 17 (noting that the allegations were "adequat[e]" and "need not be stated with . . . precision"), with id., at 35 (Murphy, J., dissenting) (arguing that the charge was inadequate). Nor does it find support from the separation-of-powers authority cited by the plurality. Indeed, Madison's praise of the separation of powers in The Federalist No. 47, quoted ante, at 602, if it has any relevance at all, merely highlights the illegitimacy of today's judicial intrusion onto core executive prerogatives in the waging of war, where executive competence is at its zenith and judicial competence at its nadir.

The plurality's newly minted clear-statement rule is also fundamentally inconsistent with the nature of the common law which, by definition, evolves and develops over time and does not, in all cases, "say what may be done." 11 Op. Atty. Gen., at 300. Similarly, it is inconsistent with the nature of warfare, which also evolves and changes over time, and for which a flexible, evolutionary common-law system is uniquely appropriate. Though the charge against Hamdan easily satisfies even the plurality's manufactured rule, see infra, at 692-706, the plurality's inflexible approach has dangerous implications for the Executive's ability to discharge his duties as Commander in Chief in future cases. We should undertake to determine whether an unlawful combatant has been charged with an offense against the law of war with an understanding that the common law of war is flexible, responsive to the exigencies of the present conflict, and deferential to the judgment of military commanders.

I

Under either the correct, flexible approach to evaluating the adequacy of Hamdan's charge, or under the plurality's new, clear-statement approach, Hamdan has been charged with conduct constituting two distinct violations of the law of war cognizable before a military commission: membership in a war-criminal enterprise and conspiracy to commit war crimes. The charging section of the indictment alleges both that Hamdan "willfully and knowingly joined an enterprise of persons who shared a common criminal purpose," App. to Pet. for Cert. 65a, and that he "conspired and agreed with [al Qaeda] to commit. . . offenses triable by military commission," ibid.

The common law of war establishes that Hamdan's willful and knowing membership in al Qaeda is a war crime chargeable before a military commission. Hamdan, a confirmed enemy combatant and member or affiliate of al Qaeda, has been charged with willfully and knowingly joining a group (al Qaeda) whose purpose is "to support violent attacks against property and nationals (both military and civilian) of the United States." Id., at 64a; 344 F. Supp. 2d, at 161. Moreover, the allegations specify that Hamdan joined and maintained his relationship with al Qaeda even though he "believed that Usama bin Laden and his associates were involved in the attacks on the U. S. Embassies in Kenya and Tanzania in August 1998, the attack on the USS COLE in October 2000, and the attacks on the United States on September 11, 2001." App. to Pet. for Cert. 65a. These allegations, against a confirmed unlawful combatant, are alone sufficient to sustain the jurisdiction of Hamdan's military commission.

For well over a century it has been established that "to unite with banditti, jayhawkers, guerillas, or any other unauthorized marauders is a high offence against the laws of war; the offence is complete when the band is organized or joined. The atrocities committed by such a band do not constitute the offence, but make the reasons, and sufficient reasons they are, why such banditti are denounced by the laws of war." 11 Op. Atty. Gen., at 312 (emphasis added). In other words, unlawful combatants, such as Hamdan, violate the law of war merely by joining an organization, such as al Qaeda, whose principal purpose is the "killing [and] disabling . . . of peaceable citizens or soldiers." Winthrop 784; see also 11 Op. Atty. Gen., at 314 ("A bushwhacker, a jayhawker, a bandit, a war rebel, an assassin, being public enemies, may be tried, condemned, and executed as offenders against the laws of war"). This conclusion is unsurprising, as it is a "cardinal principle of the law of war . . . that the civilian population must enjoy complete immunity." 4 Int'l Comm. of Red Cross, Commentary: Geneva Convention Relative to the Protection of Civilian Persons in Time of War 3 (J. Pictet gen. ed. 1958). "Numerous instances of trials, for `Violation of the laws of war,' of offenders of this description, are published in the General Orders of the years 1862 to 1866." Winthrop 784, and n. 57. Accordingly, on this basis alone, "the allegations of [Hamdan's] charge, tested by any reasonable standard, adequately allege a violation of the law of war." Yamashita, 327 U. S., at 17.

The conclusion that membership in an organization whose purpose is to violate the laws of war is an offense triable by military commission is confirmed by the experience of the military tribunals convened by the United States at Nuremberg. Pursuant to Article 10 of the Charter of the International Military Tribunal (IMT), the United States convened military tribunals "to bring individuals to trial for membership" in "a group or organization . . . declared criminal by the [IMT]." 1 Trials of War Criminals Before the Nuernberg Military Tribunals, p. XII, Art. 10 (hereinafter Trials). The IMT designated various components of four Nazi groups — the Leadership Corps, Gestapo, SD, and SS — as criminal organizations. 22 IMT, Trial of the Major War Criminals 505, 511, 517 (1948); see also T. Taylor, Anatomy of the Nuremberg Trials: A Personal Memoir 584-585 (1992). "[A] member of [such] an organization [could] be . . . convicted of the crime of membership and be punished for that crime by death." 22 IMT, at 499. Under this authority, the United States Military Tribunal at Nuremberg convicted numerous individuals for the act of knowing and voluntary membership in these organizations. For example, in Military Tribunal Case No. 1, United States v. Brandt, Karl Brandt, Karl Gebhardt, Rudolf Brandt, Joachim Mrugowsky, Wolfram Sievers, Viktor Brack, and Waldemar Hoven were convicted and sentenced to death for the crime of, inter alia, membership in an organization declared criminal by the IMT; Karl Genzken and Fritz Fischer were sentenced to life imprisonment for the same; and Helmut Poppendick was convicted of no other offense than membership in a criminal organization and sentenced to a 10-year term of imprisonment. 2 Trials 180-300. This Court denied habeas relief, 333 U. S. 836 (1948), and the executions were carried out at Landsberg prison on June 2, 1948. 2 Trials 330.

Moreover, the Government has alleged that Hamdan was not only a member of al Qaeda while it was carrying out terrorist attacks on civilian targets in the United States and abroad, but also that Hamdan aided and assisted al Qaeda's top leadership by supplying weapons, transportation, and other services. App. to Pet. for Cert. 65a-67a. These allegations further confirm that Hamdan is triable before a law-of-war military commission for his involvement with al Qaeda. See H. R. Doc. No. 65, 55th Cong., 3d Sess., 234 (1894) ("[T]here are numerous rebels . . . that . . . furnish the enemy with arms, provisions, clothing, horses and means of transportation; [such] insurgents are banding together in several of the interior counties for the purpose of assisting the enemy to rob, to maraud and to lay waste [to] the country. All such persons are by the laws of war in every civilized country liable to capital punishment" (emphasis added)); Winthrop 840 (including in the list of offenses triable by law-of-war military commissions "dealing with . . . enemies, or furnishing them with money, arms, provisions, medicines, c."). Undoubtedly, the conclusion that such conduct violates the law of war led to the enactment of Article 104 of the UCM J, which provides that "[a]ny person who . . . aids, or attempts to aid, the enemy with arms, ammunition, supplies, money, or other things . . . shall suffer death or such other punishment as a court-martial or military commission may direct." 10 U.S.C. § 904.

2

Separate and apart from the offense of joining a contingent of "uncivilized combatants who [are] not . . . likely to respect the laws of war," Winthrop 784, Hamdan has been charged with "conspir[ing] and agree[ing] with . . . the al Qaida organization . . . to commit . . . offenses triable by military commission," App. to Pet. for Cert. 65a. Those offenses include "attacking civilians; attacking civilian objects; murder by an unprivileged belligerent; and terrorism." Ibid. This, too, alleges a violation of the law of war triable by military commission.

"[T]he experience of our wars," Winthrop 839, is rife with evidence that establishes beyond any doubt that conspiracy to violate the laws of war is itself an offense cognizable before a law-of-war military commission. World War II provides the most recent examples of the use of American military commissions to try offenses pertaining to violations of the laws of war. In that conflict, the orders establishing the jurisdiction of military commissions in various theaters of operation provided that conspiracy to violate the laws of war was a cognizable offense. See Letter, General Headquarters, United States Army Forces, Pacific (Sept. 24, 1945), Record in Yamashita v. Styer, O. T. 1945, No. 672, pp. 14, 16 (Exh. F) (Order respecting the "Regulations Governing the Trial of War Criminals" provided that "participation in a common plan or conspiracy to accomplish" various offenses against the law of war was cognizable before military commissions); 1 U. N. War Crimes Commission, Law Reports of Trials of War Criminals 114-115 (1947) (reprint 1997) (hereinafter U. N. Commission) (recounting that the orders establishing World War II military commissions in the Pacific and China included "participation in a common plan or conspiracy" pertaining to certain violations of the laws of war as an offense triable by military commission). Indeed, those orders authorized trial by military commission of participation in a conspiracy to commit "`murder . . . or other inhumane acts . . . against any civilian population,'" id., at 114, which is precisely the offense Hamdan has been charged with here. And conspiracy to violate the laws of war was charged in the highest profile case tried before a World War II military commission, see Quirin, 317 U. S., at 23, and on numerous other occasions. See, e. g., Colepaugh v. Looney, 235 F. 2d 429, 431 (CAIO 1956); Green 848 (describing the conspiracy trial of Julius Otto Kuehn).

To support its contrary conclusion, ante, at 600, the plurality attempts to evade the import of Quirin (and the other World War II authorities) by resting upon this Court's failure to address the sufficiency of the conspiracy charge in the Quirin case, ante, at 605-607. But the common law of war cannot be ascertained from this Court's failure to pass upon an issue, or indeed to even mention the issue in its opinion; rather, it is ascertained by the practice and usage of war. Winthrop 839; supra, at 689-690.

The Civil War experience provides further support for the President's conclusion that conspiracy to violate the laws of war is an offense cognizable before law-of-war military commissions. Indeed, in the highest profile case to be tried before a military commission relating to that war, namely, the trial of the men involved in the assassination of President Lincoln, the charge provided that those men had "combin[ed], confederat[ed], and conspir[ed] . . . to kill and murder" President Lincoln. G. C. M. O. No. 356 (1865), reprinted in H. R. Doc. No. 314, 55th Cong., 3d Sess., 696 (1899) (hereinafter G. C. M. O. No. 356).

In addition to the foregoing high-profile example, Winthrop's treatise enumerates numerous Civil War military commission trials for conspiracy to violate the law of war. Winthrop 839, n. 5. The plurality attempts to explain these examples away by suggesting that the conspiracies listed by Winthrop are best understood as "a species of compound offense," namely, violations both of the law of war and ordinary criminal laws, rather than "stand-alone offense[s] against the law of war." Ante, at 608 (citing, as an example, murder in violation of the laws of war). But the fact that, for example, conspiracy to commit murder can at the same time violate ordinary criminal laws and the law of war, so that it is "a combination of the two species of offenses," Howland 1071, does not establish that a military commission would not have jurisdiction to try that crime solely on the basis that it was a violation of the law of war. Rather, if anything, and consistent with the principle that the common law of war is flexible and affords some level of deference to the judgments of military commanders, it establishes that military commissions would have the discretion to try the offense as (1) one against the law of war, or (2) one against the ordinary criminal laws, or (3) both.

In any event, the plurality's effort to avoid the import of Winthrop's footnote through the smokescreen of its "compound offense" theory, ante, at 607-608, cannot be reconciled with the particular charges that sustained military commission jurisdiction in the cases that Winthrop cites. For example, in the military commission trial of Henry Wirz, Charge I provided that he had been

"[m]aliciously, willfully, and traitorously . . . combining, confederating, and conspiring, together [with various other named and unnamed co-conspirators], to injure the health and destroy the lives of soldiers in the military service of the United States, then held and being prisoners of war within the lines of the so-called Confederate States, and in the military prisons thereof, to the end that the armies of the United States might be weakened and impaired, in violation of the laws and customs of war." G. C. M. O. No. 607 (1865), reprinted in H. R. Doc. No. 314, at 785 (emphasis added).

Likewise, in the military commission trial of Leger Grenfel, Charge I accused Grenfel of " [c]onspiring, in violation of the laws of war, to release rebel prisoners of war confined by authority of the United States at Camp Douglas, near Chicago, 111." G. C. M. O. No. 452 (1865), reprinted in H. R. Doc. No. 314, at 724 (emphasis added); see also G. C. M. O. No. 41, p. 20 (1864) (indictment in the military commission trial of Robert Louden charged "`[c]onspiring with the rebel enemies of the United States to embarrass and impede the military authorities in the suppression of the existing rebellion, by the burning and destruction of steamboats and means of transportation on the Mississippi river'"). These examples provide incontrovertible support for the President's conclusion that the common law of war permits military commission trials for conspiracy to violate the law of war. And they specifically contradict the plurality's conclusion to the contrary, thereby easily satisfying its requirement that the Government "make a substantial showing that the crime for which it seeks to try a defendant by military commission is acknowledged to be an offense against the law of war." Ante, at 603.

The plurality further contends, in reliance upon Winthrop, that conspiracy is not an offense cognizable before a law-of-war military commission because "it is not enough to intend to violate the law of war and commit overt acts in furtherance of that intention unless the overt acts either are themselves offenses against the law of war or constitute steps sufficiently substantial to qualify as an attempt." Ante, at 604. But Winthrop does not support the plurality's conclusion. The passage in Winthrop cited by the plurality states only that "the jurisdiction of the military commission should be restricted to cases of offence consisting in overt acts, i. e. in unlawful commissions or actual attempts to commit, and not in intentions merely." Winthrop 841 (emphasis in original). This passage would be helpful to the plurality if its subject were "conspiracy," rather than the "jurisdiction of the military commission." Winthrop is not speaking here of the requirements for a conspiracy charge, but of the requirements for all charges. Intentions do not suffice. An unlawful act — such as committing the crime of conspiracy — is necessary. Winthrop says nothing to exclude either conspiracy or membership in a criminal enterprise, both of which go beyond "intentions merely" and "consis[t of] overt acts, i. e. . . . unlawful commissions or actual attempts to commit," and both of which are expressly recognized by Winthrop as crimes against the law of war triable by military commissions. Id., at 784; id., at 839, and n. 5, 840. Indeed, the commission of an " overt ac[t]" is the traditional requirement for the completion of the crime of conspiracy, and the charge against Hamdan alleges numerous such overt acts. App. to Pet. for Cert. 65a. The plurality's approach, unsupported by Winthrop, requires that any overt act to further a conspiracy must itself be a completed war crime distinct from conspiracy — which merely begs the question the plurality sets out to answer, namely, whether conspiracy itself may constitute a violation of the law of war. And, even the plurality's unsupported standard is satisfied here. Hamdan has been charged with the overt acts of providing protection, transportation, weapons, and other services to the enemy, id., at 65a-67a, acts which in and of themselves are violations of the laws of war. See supra, at 696-697; Winthrop 839-840.

3

Ultimately, the plurality's determination that Hamdan has not been charged with an offense triable before a military commission rests not upon any historical example or authority, but upon the plurality's raw judgment of the "inability on the Executive's part here to satisfy the most basic precondition . . . for establishment of military commissions: military necessity." Ante, at 612. This judgment starkly confirms that the plurality has appointed itself the ultimate arbiter of what is quintessentially a policy and military judgment, namely, the appropriate military measures to take against those who "aided the terrorist attacks that occurred on September 11, 2001." AUMF § 2(a), 115 Stat. 224. The plurality's suggestion that Hamdan's commission is illegitimate because it is not dispensing swift justice on the battle-field is unsupportable. Ante, at 607. Even a cursory review of the authorities confirms that law-of-war military commissions have wide-ranging jurisdiction to try offenses against the law of war in exigent and nonexigent circumstances alike. See, e. g., Winthrop 839-840; see also Yamashita, 327 U. S., at 5 (military commission trial after the cessation of hostilities in the Philippines); Quirin, 317 U. S. 1 (military commission trial in Washington, D. C). Traditionally, retributive justice for heinous war crimes is as much a "military necessity" as the "demands" of "military efficiency" touted by the plurality, and swift military retribution is precisely what Congress authorized the President to impose on the September 11 attackers in the AUMF.

Today a plurality of this Court would hold that conspiracy to massacre innocent civilians does not violate the laws of war. This determination is unsustainable. The judgment of the political branches that Hamdan, and others like him, must be held accountable before military commissions for their involvement with and membership in an unlawful organization dedicated to inflicting massive civilian casualties is supported by virtually every relevant authority, including all of the authorities invoked by the plurality today. It is also supported by the nature of the present conflict. We are not engaged in a traditional battle with a nation-state, but with a worldwide, hydra-headed enemy, who lurks in the shadows conspiring to reproduce the atrocities of September 11, 2001, and who has boasted of sending suicide bombers into civilian gatherings, has proudly distributed videotapes of beheadings of civilian workers, and has tortured and dismembered captured American soldiers. But according to the plurality, when our Armed Forces capture those who are plotting terrorist atrocities like the bombing of the Khobar Towers, the bombing of the U. S. S. Cole, and the attacks of September 11 — even if their plots are advanced to the very brink of fulfillment — our military cannot charge those criminals with any offense against the laws of war. Instead, our troops must catch the terrorists "redhanded," ante, at 612, in the midst of the attack itself, in order to bring them to justice. Not only is this conclusion fundamentally inconsistent with the cardinal principle of the law of war, namely, protecting noncombatants, but it would sorely hamper the President's ability to confront and defeat a new and deadly enemy.

After seeing the plurality overturn longstanding precedents in order to seize jurisdiction over this case, ante, at 656-658 (SCALIA, J., dissenting), and after seeing them disregard the clear prudential counsel that they abstain in these circumstances from using equitable powers, ante, at 672-678, it is no surprise to see them go on to overrule one after another of the President's judgments pertaining to the conduct of an ongoing war. Those Justices who today disregard the Commander in Chief's wartime decisions, only 10 days ago deferred to the judgment of the Corps of Engineers with regard to a matter much more within the competence of lawyers, upholding that agency's wildly implausible conclusion that a storm drain is a tributary of the waters of the United States. See Rapanos v. United States, 547 U. S. 715 (2006). It goes without saying that there is much more at stake here than storm drains. The plurality's willingness to second-guess the determination of the political branches that these conspirators must be brought to justice is both unprecedented and dangerous.

III

The Court holds that even if "the Government has charged Hamdan with an offense against the law of war cognizable by military commission, the commission lacks power to proceed" because of its failure to comply with the terms of the UCMJ and the four Geneva Conventions signed in 1949. Ante, at 613. This position is untenable.

A

As with the jurisdiction of military commissions, the procedure of such commissions "has [not] been prescribed by statute," but "has been adapted in each instance to the need that called it forth." Madsen, 343 U. S., at 347-348. Indeed, this Court has concluded that "[i]n the absence of attempts by Congress to limit the President's power, it appears that, as Commander-in-Chief of the Army and Navy of the United States, he may, in time of war, establish and prescribe the jurisdiction and procedure of military commissions." Id., at 348. This conclusion is consistent with this Court's understanding that military commissions are "our common-law war courts." Id., at 346-347. As such, "[s]hould the conduct of those who compose martial-law tribunals become [a] matter of judicial determination subsequently before the civil courts, those courts will give great weight to the opinions of the officers as to what the customs of war in any case justify and render necessary." Birkhimer 534.

The Court nevertheless concludes that at least one provision of the UCMJ amounts to an attempt by Congress to limit the President's power. This conclusion is not only contrary to the text and structure of the UCMJ, but it is also inconsistent with precedent of this Court. Consistent with Madsen's conclusion pertaining to the common-law nature of military commissions and the President's discretion to prescribe their procedures, Article 36 of the UCMJ authorizes the President to establish procedures for military commissions "which shall, so far as he considers practicable, apply the principles of law and the rules of evidence generally recognized in the trial of criminal cases in the United States district courts, but which may not be contrary to or inconsistent with this chapter." 10 U.S.C. § 836(a) (emphasis added). Far from constraining the President's authority, Article 36 recognizes the President's prerogative to depart from the procedures applicable in criminal cases whenever he alone does not deem such procedures "practicable." While the procedural regulations promulgated by the Executive must not be "contrary to" the UCMJ, only a few provisions of the UCMJ mention "military commissions," see ante, at 621, n. 49, and there is no suggestion that the procedures to be employed by Hamdan's commission implicate any of those provisions.

Notwithstanding the foregoing, the Court concludes that Article 36(b) of the UCMJ, 10 U.S.C. § 836(b), which provides that "[a]ll rules and regulations made under this article shall be uniform insofar as practicable," ante, at 620, requires the President to employ the same rules and procedures in military commissions as are employed by courts-martial "`insofar as practicable,'" ante, at 622. The Court further concludes that Hamdan's commission is unlawful because the President has not explained why it is not practicable to apply the same rules and procedures to Hamdan's commission as would be applied in a trial by court-martial. Ante, at 623-624.

This interpretation of § 836(b) is unconvincing. As an initial matter, the Court fails to account for our cases interpreting the predecessor to Article 21 of the UCMJ — Article 15 of the Articles of War — which provides crucial context that bears directly on the proper interpretation of Article 36(b). Article 15 of the Articles of War provided that:

"The provisions of these articles conferring jurisdiction upon courts-martial shall not be construed as depriving military commissions, provost courts, or other military tribunals of concurrent jurisdiction in respect of offenders or offenses that by statute or by the law of war may be triable by such military commissions, provost courts, or other military tribunals." 41 Stat. 790.

In Yamashita, this Court concluded that Article 15 of the Articles of War preserved the President's unfettered authority to prescribe military commission procedure. The Court explained, "[b]y thus recognizing military commissions in order to preserve their traditional jurisdiction over enemy combatants unimpaired by the Articles, Congress gave sanction . . . to any use of the military commission contemplated by the common law of war." 327 U. S., at 20 (emphasis added); see also Quirin, 317 U. S., at 28; Madsen, 343 U. S., at 355. In reaching this conclusion, this Court treated as authoritative the congressional testimony of Judge Advocate General Crowder, who testified that Article 15 of the Articles of War was enacted to preserve the military commission as "`our common-law war court.'" Yamashita, supra, at 19, n. 7. And this Court recognized that Article 15's preservation of military commissions as common-law war courts preserved the President's Commander in Chief authority to both "establish" military commissions and to "prescribe [their] procedure[s]." Madsen, 343 U. S., at 348; id., at 348-349 (explaining that Congress had "refrain[ed] from legislating" in the area of military commission procedures, in "contras[t] with its traditional readiness to . . . prescrib[e], with particularity, the jurisdiction and procedure of United States courts-martial"); cf. Green 834 ("The military commission exercising jurisdiction under common law authority is usually appointed by a superior military commander and is limited in its procedure only by the will of that commander. Like any other common law court, in the absence of directive of superior authority to the contrary, the military commission is free to formulate its own rules of procedure").

Given these precedents, the Court's conclusion that Article 36(b) requires the President to apply the same rules and procedures to military commissions as are applicable to courts-martial is unsustainable. When Congress codified Article 15 of the Articles of War in Article 21 of the UCMJ it was "presumed to be aware of . . . and to adopt" this Court's interpretation of that provision as preserving the common-law status of military commissions, inclusive of the President's unfettered authority to prescribe their procedures. Lorillard v. Pons, 434 U. S. 575, 580 (1978). The Court's conclusion that Article 36(b) repudiates this settled meaning of Article 21 is not based upon a specific textual reference to military commissions, but rather on a one-sentence subsection providing that "[a]ll rules and regulations made under this article shall be uniform insofar as practicable." 10 U.S.C. § 836(b). This is little more than an impermissible repeal by implication. See Branch v. Smith, 538 U. S. 254, 273 (2003) (plurality opinion) ("We have repeatedly stated . . . that absent a clearly expressed congressional intention, repeals by implication are not favored" (citations and internal quotation marks omitted)). Moreover, the Court's conclusion is flatly contrary to its duty not to set aside Hamdan's commission "without the clear conviction that [it is] in conflict with the . . . laws of Congress constitutionally enacted." Quirin, supra, at 26 (emphasis added).

Nothing in the text of Article 36(b) supports the Court's sweeping conclusion that it represents an unprecedented congressional effort to change the nature of military commissions from common-law war courts to tribunals that must presumptively function like courts-martial. And such an interpretation would be strange indeed. The vision of uniformity that motivated the adoption of the UCM J, embodied specifically in Article 36(b), is nothing more than uniformity across the separate branches of the armed services. See Act of May 5, 1950, ch. 169, 64 Stat. 107 (preamble to the UCMJ explaining that the UCMJ is an Act "[t]o unify, consolidate, revise, and codify the Articles of War, the Articles for the Government of the Navy, and the disciplinary laws of the Coast Guard"). There is no indication that the UCMJ was intended to require uniformity in procedure between courts-martial and military commissions, tribunals that the UCMJ itself recognizes are different. To the contrary, the UCMJ expressly recognizes that different tribunals will be constituted in different manners and employ different procedures. See 10 U.S.C. § 866 (providing for three different types of courts-martial — general, special, and summary — constituted in different manners and employing different procedures). Thus, Article 36(b) is best understood as establishing that, so far as practicable, the rules and regulations governing tribunals convened by the Navy must be uniform with the rules and regulations governing tribunals convened by the Army. But, consistent with this Court's prior interpretations of Article 21 and over a century of historical practice, it cannot be understood to require the President to conform the procedures employed by military commissions to those employed by courts-martial.

Even if Article 36(b) could be construed to require procedural uniformity among the various tribunals contemplated by the UCMJ, Hamdan would not be entitled to relief. Under the Court's reading, the President is entitled to prescribe different rules for military commissions than for courts-martial when he determines that it is not "practicable" to prescribe uniform rules. The Court does not resolve the level of deference such determinations would be owed, however, because, in its view, "[t]he President has not . . . [determined] that it is impracticable to apply the rules for courts-martial." Ante, at 623. This is simply not the case. On the same day that the President issued Military Commission Order No. 1, the Secretary of Defense explained that "the president decided to establish military commissions because he wanted the option of a process that is different from those processes which we already have, namely, the federal court system . . . and the military court system," Dept. of Defense News Briefing on Military Commissions (Mar. 21, 2002) (remarks of Donald Rumsfeld), available at http://www.dod.gov/transcripts/2002/t03212002_t0321sd.html (as visited June 26, 2006, and available in Clerk of Court's case file) (hereinafter News Briefing), and that "[t]he commissions are intended to be different . . . because the [P]resident recognized that there had to be differences to deal with the unusual situation we face and that a different approach was needed." Ibid. The President reached this conclusion because

"we're in the middle of a war, and . . . had to design a procedure that would allow us to pursue justice for these individuals while at the same time prosecuting the war most effectively. And that means setting rules that would allow us to preserve our intelligence secrets, develop more information about terrorist activities that might be planned for the future so that we can take action to prevent terrorist attacks against the United States. . . . [T]here was a constant balancing of the requirements of our war policy and the importance of providing justice for the individuals . . . and each deviation from the standard kinds of rules that we have in our criminal courts was motivated by the desire to strike this balance between individual justice and the broader war policy." Ibid. (remarks of Douglas J. Feith, Under Secretary of Defense for Policy (emphasis added)).

The Court provides no explanation why the President's determination that employing court-martial procedures in the military commissions established pursuant to Military Commission Order No. 1 would hamper our war effort is in any way inadequate to satisfy its newly minted "practicability" requirement. On the contrary, this determination is precisely the kind for which the "Judiciary has neither aptitude, facilities nor responsibility and which has long been held to belong in the domain of political power not subject to judicial intrusion or inquiry.'" Chicago Southern Air Lines, Inc. v. Waterman S. S. Corp., 333 U. S., at 111. And, in the context of the present conflict, it is exactly the kind of determination Congress countenanced when it authorized the President to use all necessary and appropriate force against our enemies. Accordingly, the President's determination is sufficient to satisfy any practicability requirement imposed by Article 36(b).

The Court further contends that Hamdan's commission is unlawful because it fails to provide him the right to be present at his trial, as recognized in 10 U.S.C. § 839(c) (2000 ed., Supp. V). Ante, at 624. But § 839(c) applies to courts-martial, not military commissions. It provides:

"When the members of a court-martial deliberate or vote, only the members may be present. All other proceedings, including any other consultation of the members of the court with counsel or the military judge, shall be made a part of the record and shall be in the presence of the accused, the defense counsel, the trial counsel, and, in cases in which a military judge has been detailed to the court, the military judge."

In context, "all other proceedings" plainly refers exclusively to "other proceedings" pertaining to a court-martial. This is confirmed by the provision's subsequent reference to "members of the court" and to "cases in which a military judge has been detailed to the court." It is also confirmed by the other provisions of § 839, which refer only to courts-martial. See §§ 839(a)(1)-(4) ("[A]ny time after the service of charges which have been referred for trial to a court-martial composed of a military judge and members, the military judge may . . . call the court into session without the presence of the members for the purpose of" hearing motions, issuing rulings, holding arraignments, receiving pleas, and performing various procedural functions). See also § 839(b) ("Proceedings under subsection (a) shall be conducted in the presence of the accused"). Section 839(c) simply does not address the procedural requirements of military commissions.

B

The Court contends that Hamdan's military commission is also unlawful because it violates Common Article 3 of the Geneva Conventions, see ante, at 629-635. Furthermore, Hamdan contends that his commission is unlawful because it violates various provisions of the Third Geneva Convention. These contentions are untenable.

1

As an initial matter, and as the Court of Appeals concluded, both of Hamdan's Geneva Convention claims are foreclosed by Johnson v. Eisentrager, 339 U. S. 763 (1950). In that case the respondents claimed, inter alia, that their military commission lacked jurisdiction because it failed to provide them with certain procedural safeguards that they argued were required under the Geneva Conventions. Id., at 789-790. While this Court rejected the underlying merits of the respondents' Geneva Convention claims, id., at 790, it also held, in the alternative, that the respondents could "not assert . . . that anything in the Geneva Convention makes them immune from prosecution or punishment for war crimes," id., at 789. The Court explained:

"We are not holding that these prisoners have no right which the military authorities are bound to respect. The United States, by the Geneva Convention of July 27, 1929, 47 Stat. 2021, concluded with forty-six other countries, including the German Reich, an agreement upon the treatment to be accorded captives. These prisoners claim to be and are entitled to its protection. It is, however, the obvious scheme of the Agreement that responsibility for observance and enforcement of these rights is upon political and military authorities. Rights of alien enemies are vindicated under it only through protests and intervention of protecting powers as the rights of our citizens against foreign governments are vindicated only by Presidential intervention." Id., at 789, n. 14.

This alternative holding is no less binding than if it were the exclusive basis for the Court's decision. See Massachusetts v. United States, 333 U. S. 611, 623 (1948). While the Court attempts to cast Eisentrager's unqualified, alternative holding as footnote dictum, ante, at 627, it does not dispute the correctness of its conclusion, namely, that the provisions of the 1929 Geneva Convention were not judicially enforceable because that Convention contemplated that diplomatic measures by political and military authorities were the exclusive mechanisms for such enforcement. Nor does the Court suggest that the 1949 Geneva Conventions departed from this framework. See ibid. ("We may assume that `the obvious scheme' of the 1949 Conventions is identical in all relevant respects to that of the 1929 Convention").

Instead, the Court concludes that petitioner may seek judicial enforcement of the provisions of the Geneva Conventions because "they are . . . part of the law of war. And compliance with the law of war is the condition upon which the authority set forth in Article 21 is granted." Ante, at 628 (citation omitted). But Article 21 authorizes the use of military commissions; it does not purport to render judicially enforceable aspects of the law of war that are not so enforceable of their own accord. See Quirin, 317 U. S., at 28 (by enacting Article 21, "Congress has explicitly provided, so far as it may constitutionally do so, that military tribunals shall have jurisdiction to try offenders or offenses against the law of war"). The Court cannot escape Eisentrager's holding merely by observing that Article 21 mentions the law of war; indeed, though Eisentrager did not specifically consider the Court's novel interpretation of Article 21, Eisentrager involved a challenge to the legality of a World War II military commission, which, like all such commissions, found its authorization in Article 15 of the Articles of War, the predecessor to Article 21 of the UCMJ. Thus, the Court's interpretation of Article 21 is foreclosed by Eisentrager.

In any event, the Court's argument is too clever by half. The judicial nonenforceability of the Geneva Conventions derives from the fact that those Conventions have exclusive enforcement mechanisms, see Eisentrager, supra, at 789, n. 14, and this, too, is part of the law of war. The Court's position thus rests on the assumption that Article 21's reference to the "laws of war" selectively incorporates only those aspects of the Geneva Conventions that the Court finds convenient, namely, the substantive requirements of Common Article 3, and not those aspects of the Conventions that the Court, for whatever reason, disfavors, namely, the Conventions' exclusive diplomatic enforcement scheme. The Court provides no account of why the partial incorporation of the Geneva Conventions should extend only so far — and no further — because none is available beyond its evident preference to adjudicate those matters that the law of war, through the Geneva Conventions, consigns exclusively to the political branches.

Even if the Court were correct that Article 21 of the UCMJ renders judicially enforceable aspects of the law of war that are not so enforceable by their own terms, Article 21 simply cannot be interpreted to render judicially enforceable the particular provision of the law of war at issue here, namely, Common Article 3 of the Geneva Conventions. As relevant, Article 21 provides that "[t]he provisions of this chapter conferring jurisdiction upon courts-martial do not deprive military commissions . . . of concurrent jurisdiction with respect to offenders or offenses that by statute or by the law of war may be tried by military commissions." 10 U.S.C. § 821 (emphasis added). Thus, to the extent Article 21 can be interpreted as authorizing judicial enforcement of aspects of the law of war that are not otherwise judicially enforceable, that authorization only extends to provisions of the law of war that relate to whether a particular "offender" or a particular "offense" is triable by military commission. Common Article 3 of the Geneva Conventions, the sole provision of the Geneva Conventions relevant to the Court's holding, relates to neither. Rather, it relates exclusively to the particulars of the tribunal itself, namely, whether it is "regularly constituted" and whether it "afford[s] all the judicial guarantees which are recognized as indispensable by civilized peoples." Third Geneva Convention, Art. 3, ¶ 1( d), Relative to the Treatment of Prisoners of War, Aug. 12, 1949, [1955] 6 U. S. T. 3316, 3320, T. I. A. S. No. 3364.

2

In addition to being foreclosed by Eisentrager, Hamdan's claim under Common Article 3 of the Geneva Conventions is meritless. Common Article 3 applies to "armed conflict not of an international character occurring in the territory of one of the High Contracting Parties." 6 U. S. T., at 3318. "Pursuant to [his] authority as Commander in Chief and Chief Executive of the United States," the President has "accept[ed] the legal conclusion of the Department of Justice . . . that common Article 3 of Geneva does not apply to . . . al Qaeda . . . detainees, because, among other reasons, the relevant conflicts are international in scope and common Article 3 applies only to `armed conflict not of an international character.'" App. 35. Under this Court's precedents, "the meaning attributed to treaty provisions by the Government agencies charged with their negotiation and enforcement is entitled to great weight." Sumitomo Shoji America, Inc. v. Avagliano, 457 U. S. 176, 184-185 (1982); United States v. Stuart, 489 U. S. 353, 369 (1989). Our duty to defer to the President's understanding of the provision at issue here is only heightened by the fact that he is acting pursuant to his constitutional authority as Commander in Chief and by the fact that the subject matter of Common Article 3 calls for a judgment about the nature and character of an armed conflict. See generally United States v. Curtiss-Wright Export Corp., 299 U. S. 304, 320 (1936).

The President's interpretation of Common Article 3 is reasonable and should be sustained. The conflict with al Qaeda is international in character in the sense that it is occurring in various nations around the globe. Thus, it is also "occurring in the territory of" more than "one of the High Contracting Parties." The Court does not dispute the President's judgments respecting the nature of our conflict with al Qaeda, nor does it suggest that the President's interpretation of Common Article 3 is implausible or foreclosed by the text of the treaty. Indeed, the Court concedes that Common Article 3 is principally concerned with "furnish[ing] minimal protection to rebels involved in . . . a civil war," ante, at 631, precisely the type of conflict the President's interpretation envisions to be subject to Common Article 3. Instead, the Court, without acknowledging its duty to defer to the President, adopts its own, admittedly plausible, reading of Common Article 3. But where, as here, an ambiguous treaty provision ("not of an international character") is susceptible of two plausible, and reasonable, interpretations, our precedents require us to defer to the Executive's interpretation.

3

But even if Common Article 3 were judicially enforceable and applicable to the present conflict, petitioner would not be entitled to relief. As an initial matter, any claim petitioner has under Common Article 3 is not ripe. The only relevant "acts" that "are and shall remain prohibited" under Common Article 3 are "the passing of sentences and the carrying out of executions without previous judgment pronounced by a regularly constituted court affording all the judicial guarantees which are recognized as indispensable by civilized peoples." Art. 3, ¶ 1( d), 6 U. S. T., at 3318, 3320 (emphasis added). As its terms make clear, Common Article 3 is only violated, as relevant here, by the act of "passing of sentenc[e]," and thus Hamdan will only have a claim if his military commission convicts him and imposes a sentence. Accordingly, as Hamdan's claim is "contingent [upon] future events that may not occur as anticipated, or indeed may not occur at all," it is not ripe for adjudication. Texas v. United States, 523 U. S. 296, 300 (1998) (internal quotation marks omitted). Indeed, even if we assume he will be convicted and sentenced, whether his trial will be conducted in a manner so as to deprive him of "the judicial guarantees which are recognized as indispensable by civilized peoples" is entirely speculative. And premature adjudication of Hamdan's claim is especially inappropriate here because "reaching the merits of the dispute would force us to decide whether an action taken by one of the other two branches of the Federal Government was unconstitutional." Raines v. Byrd, 521 U. S. 811, 819-820 (1997).

In any event, Hamdan's military commission complies with the requirements of Common Article 3. It is plainly "regularly constituted" because such commissions have been employed throughout our history to try unlawful combatants for crimes against the law of war. This Court has recounted that history as follows:

"`By a practice dating from 1847 and renewed and firmly established during the Civil War, military commissions have become adopted as authorized tribunals in this country in time of war. . . . Their competency has been recognized not only in acts of Congress, but in executive proclamations, in ridings of the courts, and in the opinions of the Attorneys General.'" Madsen, 343 U. S., at 346, n. 8.

Hamdan's commission has been constituted in accordance with these historical precedents. As I have previously explained, the procedures to be employed by that commission, and the Executive's authority to alter those procedures, are consistent with the practice of previous American military commissions. See supra, at 706-712, and n. 15.

The Court concludes Hamdan's commission fails to satisfy the requirements of Common Article 3 not because it differs from the practice of previous military commissions but because it "deviate[s] from [the procedures] governing courts-martial." Ante, at 634. But there is neither a statutory nor historical requirement that military commissions conform to the structure and practice of courts-martial. A military commission is a different tribunal, serving a different function, and thus operates pursuant to different procedures. The 150-year pedigree of the military commission is itself sufficient to establish that such tribunals are "regularly constituted court[s]." Art. 3, ¶ 1( d), 6 U. S. T, at 3320.

Similarly, the procedures to be employed by Hamdan's commission afford "all the judicial guarantees which are recognized as indispensable by civilized peoples." Neither the Court nor petitioner disputes the Government's description of those procedures.

"Petitioner is entitled to appointed military legal counsel, 32 C.F.R. 9.4(c)(2), and may retain a civilian attorney (which he has done), 32 C.F.R. 9.4(c)(2)(iii)(B). Petitioner is entitled to the presumption of innocence, 32 C.F.R. 9.5(b), proof beyond a reasonable doubt, 32 C.F.R. 9.5(c), and the right to remain silent, 32 C.F.R. 9.5(f). He may confront witnesses against him, 32 C.F.R. 9.5(i), and may subpoena his own witnesses, if reasonably available, 32 C.F.R. 9.5(h). Petitioner may personally be present at every stage of the trial unless he engages in disruptive conduct or the prosecution introduces classified or otherwise protected information for which no adequate substitute is available and whose admission will not deprive him of a full and fair trial, 32 C.F.R. 9.5(k); Military Commission Order No. 1 (Dep't of Defense Aug. 31, 2005) § 6(B)(3) and (D)(5)(b). If petitioner is found guilty, the judgment will be reviewed by a review panel, the Secretary of Defense, and the President, if he does not designate the Secretary as the final decisionmaker. 32 C.F.R. 9.6(h). The final judgment is subject to review in the Court of Appeals for the District of Columbia Circuit and ultimately in this Court. See DTA § 1005(e)(3), 119 Stat. 2743; 28 U.S.C. 1254(1)." Brief for Respondents 4.

Notwithstanding these provisions, which in my judgment easily satisfy the nebulous standards of Common Article 3, the plurality concludes that Hamdan's commission is unlawful because of the possibility that Hamdan will be barred from proceedings and denied access to evidence that may be used to convict him. Ante, at 633-635. But, under the commissions' rules, the Government may not impose such bar or denial on Hamdan if it would render his trial unfair, a question that is clearly within the scope of the appellate review contemplated by regulation and statute.

Moreover, while the Executive is surely not required to offer a particularized defense of these procedures prior to their application, the procedures themselves make clear that Hamdan would only be excluded (other than for disruption) if it were necessary to protect classified (or classifiable) intelligence, Dept. of Defense, Military Commission Order No. 1, § 6(B)(3) (Aug. 31, 2005), including the sources and methods for gathering such intelligence. The Government has explained that "we want to make sure that these proceedings, which are going on in the middle of the war, do not interfere with our war effort and . . . because of the way we would be able to handle interrogations and intelligence information, may actually assist us in promoting our war aims." News Briefing (remarks of Douglas J. Feith, Under Secretary of Defense for Policy). And this Court has concluded, in the very context of a threat to reveal our Nation's intelligence gathering sources and methods, that "[i]t is `obvious and unarguable' that no governmental interest is more compelling than the security of the Nation," Haig, 453 U. S., at 307 (quoting Aptheker v. Secretary of State, 378 U. S. 500, 509 (1964)), and that "Measures to protect the secrecy of our Government's foreign intelligence operations plainly serve these interests," Haig, supra, at 307. See also Snepp v. United States, 444 U. S. 507, 509, n. 3 (1980) ( per curiam) ("The Government has a compelling interest in protecting both the secrecy of information important to our national security and the appearance of confidentiality so essential to the effective operation of our foreign intelligence service"); Curtiss-Wright, 299 U. S., at 320. This interest is surely compelling here. According to the Government, "[b]ecause al Qaeda operates as a clandestine force relying on sleeper agents to mount surprise attacks, one of the most critical fronts in the current war involves gathering intelligence about future terrorist attacks and how the terrorist network operates — identifying where its operatives are, how it plans attacks, who directs operations, and how they communicate." Brief for United States in No. 03-4792, United States v. Moussaoui (CA4), p. 9. We should not rule out the possibility that this compelling interest can be protected, while at the same time affording Hamdan (and others like him) a fair trial.

In these circumstances, "civilized peoples" would take into account the context of military commission trials against unlawful combatants in the war on terrorism, including the need to keep certain information secret in the interest of preventing future attacks on our Nation and its foreign installations so long as it did not deprive the accused of a fair trial. Accordingly, the President's understanding of the requirements of Common Article 3 is entitled to "great weight." See supra, at 718.

4

In addition to Common Article 3, which applies to conflicts "not of an international character," Hamdan also claims that he is entitled to the protections of the Third Geneva Convention, which applies to conflicts between two or more High Contracting Parties. There is no merit to Hamdan's claim.

Article 2 of the Convention provides that "the present Convention shall apply to all cases of declared war or of any other armed conflict which may arise between two or more of the High Contracting Parties." 6 U. S. T., at 3318. "Pursuant to [his] authority as Commander in Chief and Chief Executive of the United States," the President has determined that the Convention is inapplicable here, explaining that "none of the provisions of Geneva apply to our conflict with al Qaeda in Afghanistan or elsewhere throughout the world because, among other reasons, al Qaeda is not a High Contracting Party." App. 35. The President's findings about the nature of the present conflict with respect to members of al Qaeda operating in Afghanistan represents a core exercise of his Commander in Chief authority that this Court is bound to respect. See Prize Cases, 2 Black, at 670.

* * *

For these reasons, I would affirm the judgment of the Court of Appeals.

JUSTICE ALITO, with whom JUSTICE SCALIA and JUSTICE THOMAS join in Parts I — III, dissenting.

For the reasons set out in JUSTICE SCALIA'S dissent, which I join, I would hold that we lack jurisdiction. On the merits, I join JUSTICE THOMAS' dissent with the exception of Parts I, II-C-1, and III-B-2, which concern matters that I find unnecessary to reach. I add the following comments to provide a further explanation of my reasons for disagreeing with the holding of the Court.

I

The holding of the Court, as I understand it, rests on the following reasoning. A military commission is lawful only if it is authorized by 10 U.S.C. § 821; this provision permits the use of a commission to try "offenders or offenses" that "by statute or by the law of war may be tried by" such a commission; because no statute provides that an offender such as petitioner or an offense such as the one with which he is charged may be tried by a military commission, he may be tried by military commission only if the trial is authorized by "the law of war"; the Geneva Conventions are part of the law of war; and Common Article 3 of the Conventions prohibits petitioner's trial because the commission before which he would be tried is not "a regularly constituted court," Third Geneva Convention, Art. 3, ¶ 1( d), Relative to the Treatment of Prisoners of War, Aug. 12, 1949, [1955] 6 U. S. T. 3316, 3320, T. I. A. S. No. 3364. I disagree with this holding because petitioner's commission is "a regularly constituted court."

Common Article 3 provides as follows:

"In the case of armed conflict not of an international character occurring in the territory of one of the High Contracting Parties, each Party to the conflict shall be bound to apply, as a minimum, the following provisions:

"(1) . . . [T]he following acts are and shall remain prohibited . . .:

"( d) [T]he passing of sentences and the carrying out of executions without previous judgment pronounced by a regularly constituted court affording all the judicial guarantees which are recognized as indispensable by civilized peoples." Id., at 3318-3320 (emphasis added).

Common Article 3 thus imposes three requirements. Sentences may be imposed only by (1) a "court" (2) that is "regularly constituted" and (3) that affords "all the judicial guarantees which are recognized as indispensable by civilized peoples." Id., at 3320.

I see no need here to comment extensively on the meaning of the first and third requirements. The first requirement is largely self-explanatory, and, with respect to the third, I note only that on its face it imposes a uniform international standard that does not vary from signatory to signatory.

The second element ("regularly constituted") is the one on which the Court relies, and I interpret this element to require that the court be appointed or established in accordance with the appointing country's domestic law. I agree with the Court, see ante, at 632, n. 64, that, as used in Common Article 3, the term "regularly" is synonymous with "properly." The term "constitute" means "appoint," "set up," or "establish," Webster's Third New International Dictionary 486 (1961), and therefore "regularly constituted" means properly appointed, set up, or established. Our cases repeatedly use the phrases "regularly constituted" and "properly constituted" in this sense. See, e. g., Hamdi v. Rumsfeld, 542 U.S. 507, 538 (2004) (plurality opinion of O'Connor, J.); Nguyen v. United States, 539 U. S. 69, 83 (2003); Ryder v. United States, 515 U. S. 177, 187 (1995); Williams v. Bruffy, 96 U. S. 176, 185 (1878).

In order to determine whether a court has been properly appointed, set up, or established, it is necessary to refer to a body of law that governs such matters. I interpret Common Article 3 as looking to the domestic law of the appointing country because I am not aware of any international law standard regarding the way in which such a court must be appointed, set up, or established, and because different countries with different government structures handle this matter differently. Accordingly, "a regularly constituted court" is a court that has been appointed, set up, or established in accordance with the domestic law of the appointing country.

II

In contrast to this interpretation, the opinions supporting the judgment today hold that the military commission before which petitioner would be tried is not "a regularly constituted court" (1) because "no evident practical need explains" why its "structure and composition . . . deviate from conventional court-martial standards," ante, at 647 (KENNEDY, J., concurring in part); see also ante, at 632-633 (opinion of the Court); and (2) because, contrary to 10 U.S.C. § 836(b), the procedures specified for use in the proceeding before the military commission impermissibly differ from those provided under the Uniform Code of Military Justice (UCMJ) for use by courts-martial, ante, at 615-625 (opinion of the Court); ante, at 651-653 (KENNEDY, J., concurring in part). I do not believe that either of these grounds is sound.

A

I see no basis for the Court's holding that a military commission cannot be regarded as "a regularly constituted court" unless it is similar in structure and composition to a regular military court or unless there is an "evident practical need" for the divergence. There is no reason why a court that differs in structure or composition from an ordinary military court must be viewed as having been improperly constituted. Tribunals that vary significantly in structure, composition, and procedures may all be "regularly" or "properly" constituted. Consider, for example, a municipal court, a state trial court of general jurisdiction, an Article I federal trial court, a federal district court, and an international court, such as the International Criminal Tribunal for the former Yugoslavia. Although these courts are "differently constituted" and differ substantially in many other respects, they are all "regularly constituted."

If Common Article 3 had been meant to require trial before a country's military courts or courts that are similar in structure and composition, the drafters almost certainly would have used language that expresses that thought more directly. Other provisions of the Convention Relative to the Treatment of Prisoners of War refer expressly to the ordinary military courts and expressly prescribe the "uniformity principle" that JUSTICE KENNEDY sees in Common Article 3, see ante, at 643-644. Article 84 provides that "[a] prisoner of war shall be tried only by a military court, unless the existing laws of the Detaining Power expressly permit the civil courts to try a member of the armed forces of the Detaining Power in respect of the particular offence alleged to have been committed by the prisoner of war." 6 U. S. T., at 3382. Article 87 states that "[p]risoners of war may not be sentenced by the military authorities and courts of the Detaining Power to any penalties except those provided for in respect of members of the armed forces of the said Power who have committed the same acts." Id., at 3384. Similarly, Article 66 of the Geneva Convention Relative to the Protection of Civilian Persons in Time of War — a provision to which the Court looks for guidance in interpreting Common Article 3, see ante, at 632 — expressly provides that civilians charged with committing crimes in occupied territory may be handed over by the occupying power "to its properly constituted, non-political military courts, on condition that the said courts sit in the occupied country." 6 U. S. T. 3516, 3558-3560, T. I. A. S. No. 3365. If Common Article 3 had been meant to incorporate a "uniformity principle," it presumably would have used language like that employed in the provisions noted above. For these reasons, I cannot agree with the Court's conclusion that the military commission at issue here is not a "regularly constituted court" because its structure and composition differ from those of a court-martial.

Contrary to the suggestion of the Court, see ante, at 632, the commentary on Article 66 of the Fourth Geneva Convention does not undermine this conclusion. As noted, Article 66 permits an occupying power to try civilians in its "properly constituted, non-political military courts," 6 U. S. T., at 3558. The commentary on this provision states:

"The courts are to be `regularly constituted.' This wording definitely excludes all special tribunals. It is the ordinary military courts of the Occupying Power which will be competent." 4 Int'l Comm. of Red Cross, Commentary: Geneva Convention Relative to the Protection of Civilian Persons in Time of War 340 (J. Pictet gen. ed. 1958) (hereinafter GCIV Commentary).

The Court states that this commentary "defines `"regularly constituted"' tribunals to include `ordinary military courts' and `definitely exclud[e] all special tribunals.'" Ante, at 632 (alteration in original). This much is clear from the commentary itself. Yet the mere statement that a military court is a regularly constituted tribunal is of no help in addressing petitioner's claim that his commission is not such a tribunal. As for the commentary's mention of "special tribunals," it is doubtful whether we should take this gloss on Article 66 — which prohibits an occupying power from trying civilians in courts set up specially for that purpose — to tell us much about the very different context addressed by Common Article 3.

But even if Common Article 3 recognizes this prohibition on "special tribunals," that prohibition does not cover petitioner's tribunal. If "special" means anything in contradistinction to "regular," it would be in the sense of "special" as "relating to a single thing," and "regular" as "uniform in course, practice, or occurrence." Webster's Third New International Dictionary 2186, 1913. Insofar as respondents propose to conduct the tribunals according to the procedures of Military Commission Order No. 1 and orders promulgated thereunder — and nobody has suggested respondents intend otherwise — then it seems that petitioner's tribunal, like the hundreds of others respondents propose to conduct, is very much regular and not at all special.

B

I also disagree with the Court's conclusion that petitioner's military commission is "illegal," ante, at 625, because its procedures allegedly do not comply with 10 U.S.C. § 836. Even if § 836(b), unlike Common Article 3, does impose at least a limited uniformity requirement amongst the tribunals contemplated by the UCMJ, but see ante, at 711-712 (THOMAS, J., dissenting), and even if it is assumed for the sake of argument that some of the procedures specified in Military Commission Order No. 1 impermissibly deviate from court-martial procedures, it does not follow that the military commissions created by that order are not "regularly constituted" or that trying petitioner before such a commission would be inconsistent with the law of war. If Congress enacted a statute requiring the federal district courts to follow a procedure that is unconstitutional, the statute would be invalid, but the district courts would not. Likewise, if some of the procedures that may be used in military commission proceedings are improper, the appropriate remedy is to proscribe the use of those particular procedures, not to out-law the commissions. I see no justification for striking down the entire commission structure simply because it is possible that petitioner's trial might involve the use of some procedure that is improper.

III

Returning to the three elements of Common Article 3 — (1) a court, (2) that is appointed, set up, and established in compliance with domestic law, and (3) that respects universally recognized fundamental rights — I conclude that all of these elements are satisfied in this case.

A

First, the commissions qualify as courts.

Second, the commissions were appointed, set up, and established pursuant to an order of the President, just like the commission in Ex parte Quirin, 317 U. S. 1 (1942), and the Court acknowledges that Quirin recognized that the statutory predecessor of 10 U.S.C. § 821 "preserved" the President's power "to convene military commissions," ante, at 593. Although JUSTICE KENNEDY concludes that "an acceptable degree of independence from the Executive is necessary to render a commission `regularly constituted' by the standards of our Nation's system of justice," ante, at 645, he offers no support for this proposition (which in any event seems to be more about fairness or integrity than regularity). The commission in Quirin was certainly no more independent from the Executive than the commissions at issue here, and 10 U.S.C. §§ 821 and 836 do not speak to this issue.

Finally, the commission procedures, taken as a whole, and including the availability of review by a United States Court of Appeals and by this Court, do not provide a basis for deeming the commissions to be illegitimate. The Court questions the following two procedural rules: the rule allowing the Secretary of Defense to change the governing rules "`from time to time'" (which does not rule out midtrial changes), see ante, at 633, n. 65 (opinion of the Court); ante, at 645 (KENNEDY, J., concurring in part), and the rule that permits the admission of any evidence that would have "`probative value to a reasonable person'" (which departs from our legal system's usual rules of evidence), see ante, at 614-615, 623 (opinion of the Court); ante, at 651-653 (KENNEDY, J., concurring in part). Neither of these two rules undermines the legitimacy of the commissions.

Surely the entire commission structure cannot be stricken merely because it is possible that the governing rules might be changed during the course of one or more proceedings. If a. change is made and applied during the course of an ongoing proceeding and if the accused is found guilty, the validity of that procedure can be considered in the review proceeding for that case. After all, not every midtrial change will be prejudicial. A midtrial change might amend the governing rules in a way that is inconsequential or actually favorable to the accused.

As for the standard for the admission of evidence at commission proceedings, the Court does not suggest that this rule violates the international standard incorporated into Common Article 3 ("the judicial guarantees which are recognized as indispensable by civilized peoples," 6 U. S. T., at 3320). Rules of evidence differ from country to country, and much of the world does not follow aspects of our evidence rules, such as the general prohibition against the admission of hearsay. See, e. g., Blumenthal, Shedding Some Light on Calls for Hearsay Reform: Civil Law Hearsay Rules in Historical and Modern Perspective, 13 Pace Int'l L. Rev. 93, 96-101 (2001). If a particular accused claims to have been unfairly prejudiced by the admission of particular evidence, that claim can be reviewed in the review proceeding for that case. It makes no sense to strike down the entire commission structure based on speculation that some evidence might be improperly admitted in some future case.

In sum, I believe that Common Article 3 is satisfied here because the military commissions (1) qualify as courts, (2) that were appointed and established in accordance with domestic law, and (3) any procedural improprieties that might occur in particular cases can be reviewed in those cases.

B

The commentary on Common Article 3 supports this interpretation. The commentary on Common Article 3, ¶ 1( d), in its entirety states:

"[A]lthough [sentences and executions without a proper trial] were common practice until quite recently, they are nevertheless shocking to the civilized mind. . . . Sentences and executions without previous trial are too open to error. `Summary justice' may be effective on account of the fear it arouses . . ., but it adds too many further innocent victims to all the other innocent victims of the conflict. All civilized nations surround the administration of justice with safeguards aimed at eliminating the possibility of judicial errors. The Convention has rightly proclaimed that it is essential to do this even in time of war. We must be very clear about one point: it is only `summary' justice which it is intended to prohibit. No sort of immunity is given to anyone under this provision. There is nothing in it to prevent a person presumed to be guilty from being arrested and so placed in a position where he can do no further harm; and it leaves intact the right of the State to prosecute, sentence and punish according to the law." GCIV Commentary 39 (emphasis added).

It seems clear that the commissions at issue here meet this standard. Whatever else may be said about the system that was created by Military Commission Order No. 1 and augmented by the Detainee Treatment Act, § 1005(e)(1), 119 Stat. 2742, this system — which features formal trial procedures, multiple levels of administrative review, and the opportunity for review by a United States Court of Appeals and by this Court — does not dispense "summary justice."

* * *

For these reasons, I respectfully dissent.