Freytag, 501 U.S. at 894 n.2, 111 S.Ct. 2631. The agency's forfeiture argument leans heavily on the logic of Ciena Corporation v. Oyster Optics, LLC, 958 F.3d 1157 (Fed. Cir. 2020). There, the plaintiff "affirmatively sought a ruling" from the Patent Board, and "was content to have the assigned Board judges adjudicate its invalidity challenges until the Board ruled against it."

We have repeatedly found that a party's failure to raise an Appointments Clause challenge in its opening brief constitutes forfeiture even when the argument was raised before the termination of direct appeal and immediately after our decision in Arthrex. See, e.g., Ciena Corp. v. Oyster Optics, LLC, 958 F.3d 1157, 1161 (Fed. Cir. 2020); Custome-dia Techs., LLC v. Dish Network Corp., 941 F.3d 1173, 1175 (Fed. Cir. 2019) (per curiam); Sanofi-Aventis Deutschland GMBH v. Mylan Pharm. Inc., 791 Fed.Appx. 916, 928 n.4 (Fed. Cir. 2019) (nonprecedential); see also Vivint v. Alarm.com Inc., 856 Fed.Appx. 300, 304 (Fed. Cir. 2021) (nonprecedential) (finding forfeiture when the party failed to raise the issue in its first appeal). Odyssey's forfeiture is even clearer than those in the previous cases because it never raised its Appointments Clause challenge on direct appeal and only argued this point in its collateral challenge to the Board's decision.

As Billard recognizes, however, that general rule can yield in cases involving "structural concerns regarding separation of powers." Ciena Corp. v. Oyster Optics, LLC, 958 F.3d 1157, 1160 (Fed. Cir. 2020) (citing Freytag v. Comm'r, 501 U.S. 868, 872-93, 111 S.Ct. 2631, 115 L.Ed.2d 764 (1991)). As the district court observed, several courts of appeals have placed the ministerial exception in this category.

Even if Medtronic forfeited these arguments, an issue we do not decide, we have the discretion to reach them on appeal. Ciena Corp. v. Oyster Optics, LLC, 958 F.3d 1157, 1161 (Fed. Cir. 2020) ("[I]t is a discretionary decision to forgive waivers of non-jurisdictional challenges . . . ."). A. SIDE OPENING CLAIMS

Even if Medtronic forfeited these arguments, an issue we do not decide, we have the discretion to reach them on appeal. Ciena Corp. v. Oyster Optics, LLC, 958 F.3d 1157, 1161 (Fed. Cir. 2020) ("[I]t is a discretionary decision to forgive waivers of non-jurisdictional challenges . . . ."). A. ONE-FRENCH CLAIMS

I As a preliminary matter, Centripetal (but not the USPTO) argues that PAN forfeited its Appointments Clause challenge by seeking to initiate IPR and PGR proceedings, relying on our decision in Ciena Corp. v. Oyster Optics, LLC , 958 F.3d 1157 (Fed. Cir. 2020). In Ciena , we held that a petitioner forfeited its Appointments Clause challenge to a final written decision where it "was content to have the assigned Board judges adjudicate its invalidity challenges until the Board ruled against it" and only afterwards asserted that the members of the panel "were not appointed in compliance with the Appointments Clause."

The Director opposes. The Supreme Court's decision in Arthrex did not disturb our holding in Ciena Corp. v. Oyster Optics, LLC , 958 F.3d 1157 (Fed. Cir. 2020), in which we held that a petitioner had forfeited its Appointments Clause challenge because "unlike the patent owner in Arthrex , [the petitioner] requested that the Board adjudicate its petition [and] thus, affirmatively sought a ruling from the Board members, regardless of how they were appointed." Id. at 1159.

Given these realities, there was simply no settled or firmly established principle upended by Arthrex. As we explained in Ciena Corp. v. Oyster Optics, LLC, 958 F.3d 1157, 1161 (Fed. Cir. 2020), moreover, while courts have discretion to forgive waivers of non-jurisdictional challenges, such as Appointments Clause challenges, they also have the discretion to decline to do so. As we said there, though we forgave forfeiture in Arthrex itself to address an important, structural question of first impression, we remain free to impose standard principles of waiver in later cases raising the same challenge.