"The essence of due process is basic fairness in procedure." deKoevend v. Board of Educ. of West End Sch. Dist. RE-2, 688 P.2d 219, 227 (Colo. 1984) (relying on In re Murchison, 349 U.S. 133 (1955); Lamm v. Barber, 192 Colo. 511, 565 P.2d 538 (1977) (disapproved on other grounds); Mountain States Tel. and Tel. Co. v. Department of Labor and Employment, 184 Colo. 334, 520 P.2d 586 (1974)); see Van Sickle v. Boyes, 797 P.2d 1267, 1273 (Colo. 1990). "Whether particular procedures adopted to review determinations affecting property interests satisfy due process standards depends upon the circumstances of the particular case."

In other words, the prohibition on retrospective legislation prevents the legislature from changing the rules after the fact because to do so would be unjust. SeeVan Sickle v. Boyes, 797 P.2d 1267, 1271 (Colo. 1990) ("The purpose of the constitutional ban of retrospective legislation ... is to prevent the unfairness that results from changing the legal consequences of an act after the act has occurred.").

The purpose of this proscription is to prevent unfairness that would result from changing the consequences of an act after that act has occurred. Van Sickle v. Boyes, 797 P.2d 1267, 1271 (Colo. 1990). A statute is retrospective if it "`takes away or impairs vested rights acquired under existing laws, or creates a new obligation, imposes a new duty, or attaches a new disability, in respect to transactions or considerations already past.'"

It is well settled that an act is deemed to be violative of this constitutional prohibition if it "'["]takes away or impairs vested rights acquired under existing laws, or creates a new obligation, imposes a new duty, or attaches a new disability, in respect to transactions or considerations already past.["]'" P-W Invs., Inc. v. City of Westminster, 655 P.2d 1365, 1371 (Colo. 1982) (quoting Denver, S. Park Pac. Ry., 4 Colo. at 167 (quoting Society for the Propagation of the Gospel v. Wheeler, 22 F. Cas. 756, 767 (C.C.D.N.H. 1814) (No. 13,156))); accord D.K.B., 843 P.2d at 1332; Committee for Better Health Care for all Colo. Citizens v. Meyer, 830 P.2d 884, 891 (Colo. 1992); Smith, Harst Assocs., 803 P.2d at 966; Van Sickle v. Boyes, 797 P.2d 1267, 1270-71 (Colo. 1990); Qualls, Inc. v. Berryman, 789 P.2d 1095, 1099 (Colo. 1990); Continental Title, 645 P.2d at 1314; Spiker v. City of Lakewood, 198 Colo. 528, 532-33, 603 P.2d 130, 133 (1979); Moore v. Chalmers-Galloway Live Stock Co., 90 Colo. 548, 554, 10 P.2d 950, 952 (1932). Consequently, a "vested right" has an "independent existence," D.K.B., 843 P.2d at 1331, in the sense that once it vests it is no longer dependent for its assertion upon the common law or statute under which it may have been acquired.

Indeed, there is a presumption of correctness afforded to the administrative body's conclusion. Van Sickle v. Boyes, 797 P.2d. 1267, 1272 (Colo. 1984) (citing Hadley v. Moffat Cnty. Sch. Dist. RE-1, 381 P.2d 938, 944 (Colo. 1984)).

However, a landowner is not constitutionally entitled to use its property in a manner that results in the maximum attainable profit. Van Sickle v. Boyes, 797 P.2d 1267 (Colo. 1990); see also Trailer Haven, 81 P.3d 1132, 1137. In questions of taking, the Court is concerned with whether the owner is foreclosed from all reasonable use of the property.

A taking may be effected by the government's physical occupation of the land or by regulation. While a landowner is not entitled to the most beneficial use of his or her land, see Penn Cent. Transp. Co. v. New York City, 438 U.S. 104, 125 (1978); Goldblatt v. Town of Hempstead, 369 U.S. 590, 592 (1962); Van Sickle v. Boyes, 797 P.2d 1267, 1271 (Colo. 1990); Sellon v. City of Manitou Springs, 745 P.2d 229, 234 (Colo. 1987), extensive regulatory interference warrants compensation.Pennsylvania Coal Co. v. Mahon, 260 U.S. 393, 415 (1922) ("The general rule at least is, that while property may be regulated to a certain extent, if regulation goes too far it will be recognized as a taking.").

City of Greenwood Village v. Petitioners for Proposed City of Centennial, 3 P.3d 427, 444 (Colo.2000). If the law was intended to apply retroactively, the question of constitutionality rests on whether the legislation impairs a vested right or creates a new obligation. Id.; see also Van Sickle v. Boyes, 797 P.2d 1267, 1271–72 (Colo.1990). If the retroactive application of the legislation violates the constitutional prohibition on ex post facto laws, it is deemed retrospective and, as such, is invalid. Greenwood Village, 3 P.3d at 444;Van Sickle, 797 P.2d at 1271–72.

An abuse of discretion occurs when a governmental body issues a decision that is not reasonably supported by any competent evidence in the record. Van Sickle v. Boyes, 797 P.2d 1267 (Colo. 1990); Carney v. Civil Serv. Comm'n, 30 P.3d 861 (Colo.App. 2001). "No competent evidence" means that the governmental body's decision is "so devoid of evidentiary support that it can only be explained as an arbitrary and capricious exercise of authority."

Historically, Colorado courts have held that whether there is a taking within the meaning of Colo. Const. art. II, § 15 is determined by whether a government regulation forecloses all reasonable use of property. Jafay v. Board of County Commissioners, supra (issue central to a taking inquiry claim is whether the governmental regulation as applied to the aggrieved landowner's property forecloses all reasonable use of that property); Van Sickle v. Boyes, 797 P.2d 1267 (Colo. 1990) (enforcement of safety code did not constitute a taking because enforcement did not deprive owner of all reasonable use of building);Sellon v. City of Manitou Springs, 745 P.2d 229 (Colo. 1987) (landowners failed to prove they could not put their property to any reasonable use); Bird v. City Colorado Springs, supra (landowner must show that he has been deprived of all reasonable uses of his land).