Justice O'Connor delivered the opinion of the Court.

The Prison Litigation Reform Act of 1995 (PLRA) establishes standards for the entry and termination of prospective relief in civil actions challenging prison conditions. If prospective relief under an existing injunction does not satisfy these standards, a defendant or intervener is entitled to "immediate termination" of that relief. And under the PLRA's "automatic stay" provision, a motion to terminate prospective relief "shall operate as a stay" of that relief during the period beginning 30 days after the filing of the motion (extendable to up to 90 days for "good cause") and ending when the court rules on the motion.

The superintendent of Indiana's Pendleton Correctional Facility, which is currently operating under an ongoing injunction to remedy violations of the Eighth Amendment regarding conditions of confinement, filed a motion to terminate prospective relief under the PLRA. Respondent prisoners moved to enjoin the operation of the automatic stay provision of 3626(e)(2), arguing that it is unconstitutional. The District Court enjoined the stay, and the Court of Appeals for the Seventh Circuit affirmed. We must decide whether a district court may enjoin the operation of the PLRA's automatic stay provision and, if not, whether that provision violates separation of powers principles.

I

B

In 1996, Congress enacted the PLRA. [Under that Act,] a court "shall not grant or approve any prospective relief unless the court finds that such relief is narrowly drawn, extends no further than necessary to correct the violation of the Federal right, and is the least intrusive means necessary to correct the violations of the Federal right." 18 U.S.C. 3626(a)(1)(A). The same criteria apply to existing injunctions, and a defendant or intervenor may move to terminate prospective relief that does not meet this standard. See 3626(b)(2). The PLRA also requires courts to rule "promptly" on motions to terminate prospective relief.

Finally, the provision at issue here, 3626(e)(2), dictates that, in certain circumstances, prospective relief shall be stayed pending resolution of a motion to terminate.

C

The Court of Appeals for the Seventh Circuit conclud[ed] that although 3626(e)(2) precluded courts from exercising their equitable powers to enjoin operation of the automatic stay, the statute, so construed, was unconstitutional on separation of powers grounds. [T]he court characterized 3626(e)(2) as "a self-executing legislative determination that a specific decree of a federal court must be set aside at least for a period of time." As such, it concluded that 3626(e)(2) directly suspends a court order in violation of the separation of powers doctrine under Plaut v. Spendthrift Farm, Inc., 514 U.S. 211 (1995), and mandates a particular rule of decision, at least during the pendency of the 3626(b)(2) termination motion, contrary to United States v. Klein, 80 U.S. 128 (1872).

III

The Constitution enumerates and separates the powers of the three branches of government in Articles I, II, and III, and it is this "very structure" of the Constitution that exemplifies the concept of separation of powers. INS v. Chadha, 462 U.S. 919, 946 (1983). While the boundaries between the three branches are not "'hermetically' sealed," see id. at 951, the Constitution prohibits one branch from encroaching on the central prerogatives of another. The powers of the Judicial Branch are set forth in Article III, 1. As we explained in Plaut v. Spendthrift Farm, Inc., 514 U.S. at 218-19, Article III "gives the Federal Judiciary the power, not merely to rule on cases, but to decide them, subject to review only by superior courts in the Article III hierarchy."

Respondent prisoners contend that 3626(e)(2) encroaches on the central prerogatives of the Judiciary and thereby violates the separation of powers doctrine. It does this, the prisoners assert, by legislatively suspending a final judgment of an Article III court in violation of Plaut and Hayburn's Case, 2 U.S. 408 (1792). According to the prisoners, the remedial order governing living conditions at the Pendleton Correctional Facility is a final judgment of an Article III court, and 3626(e)(2) constitutes an impermissible usurpation of judicial power because it commands the district court to suspend prospective relief under that order, albeit temporarily. An analysis of the principles underlying Hayburn's Case and Plaut, as well as an examination of 3626(e)(2)'s interaction with the other provisions of 3626, makes clear that 3626(e)(2) does not offend these separation of powers principles.

Hayburn's Case arose out of a 1792 statute that authorized pensions for veterans of the Revolutionary War. The statute provided that the circuit courts were to review the applications and determine the appropriate amount of the pension, but that the Secretary of War had the discretion either to adopt or reject the courts' findings. 2 U.S. at 409-10. Although this Court did not reach the constitutional issue in Hayburn's Case, the statements of five Justices, acting as circuit judges, were reported, and we have since recognized that the case "stands for the principle that Congress cannot vest review of the decisions of Article III courts in officials of the Executive Branch." Plaut, 514 U.S. at 218. As we recognized in Plaut, such an effort by a coequal branch to "annul a final judgment" is "'an assumption of Judicial power' and therefore forbidden." Id. at 224.

Unlike the situation in Hayburn's Case, 3626(e)(2) does not involve the direct review of a judicial decision by officials of the Legislative or Executive branches. Nonetheless, the prisoners suggest that 3626(e)(2) falls within Hayburn's prohibition against an indirect legislative "suspension" or reopening of a final judgment, such as that addressed in Plaut. In Plaut, we held that a federal statute that required federal courts to reopen final judgments that had been entered before the statute's enactment was unconstitutional on separation of powers grounds. 514 U.S. at 211. The plaintiffs had brought a civil securities fraud action seeking money damages. Id. at 213. While that action was pending, we ruled in Lampf, Pleva, Lipkind, Prupis & Petigrow v. Gilbertson, 501 U.S. 350 (1991), that such suits must be commenced within one year after the discovery of the facts constituting the violation and within three years after such violation. In light of this intervening decision, the Plaut plaintiffs' suit was untimely, and the District Court accordingly dismissed the action as time barred. 514 U.S. at 214. After the judgment dismissing the case had become final, Congress enacted a statute providing for the reinstatement of those actions, including the Plaut plaintiffs', that had been dismissed under Lampf but that would have been timely under the previously applicable statute of limitations. 514 U.S. at 215.

We concluded that this retroactive command that federal courts reopen final judgments exceeded Congress' authority. Id. at 218-19. The decision of an inferior court within the Article III hierarchy is not the final word of the department (unless the time for appeal has expired), and "[i]t is the obligation of the last court in the hierarchy that rules on the case to give effect to Congress's latest enactment, even when that has the effect of overturning the judgment of an inferior court, since each court, at every level, must 'decide according to existing laws.'" Id. at 227. But once a judicial decision achieves finality, it "becomes the last word of the judicial department." 514 U.S. at 227. And because Article III "gives the Federal Judiciary the power, not merely to rule on cases, but to decide them, subject to review only by superior courts in the Article III hierarchy," id. at 218-19, the "judicial Power is one to render dispositive judgments," and Congress cannot retroactively command Article III courts to reopen final judgments, id. at 219.

Plaut, however, was careful to distinguish the situation before the Court in that case legislation that attempted to reopen the dismissal of a suit seeking money damages from legislation that "altered the prospective effect of injunctions entered by article III courts." 514 U.S. at 232. Prospective relief under a continuing, executory decree remains subject to alteration due to changes in the underlying law. This conclusion follows from our decisions in Pennsylvania v. Wheeling & Belmont Bridge Co., 54 U.S. 518 (1852) (Wheeling Bridge I), and Pennsylvania v. Wheeling & Belmont Bridge Co., 59 U.S. 421 (1856) (Wheeling Bridge II).

In Wheeling Bridge I, we held that a bridge across the Ohio River, because it was too low, unlawfully "obstruct[ed] the navigation of the Ohio," and ordered that the bridge be raised or permanently removed. 54 U.S. at 578. Shortly thereafter, Congress enacted legislation declaring the bridge to be a "lawful structur[e]," establishing the bridge as a "'post-road for the passage of the mails of the United States,'" and declaring that the Wheeling and Belmont Bridge Company was authorized to maintain the bridge at its then-current site and elevation. Wheeling Bridge II, 59 U.S. at 429. After the bridge was destroyed in a storm, Pennsylvania sued to enjoin the bridge's reconstruction, arguing that the statute legalizing the bridge was unconstitutional because it effectively annulled the Court's decision in Wheeling Bridge I. We rejected that argument, concluding that the decree in Wheeling Bridge I provided for ongoing relief by "directing the abatement of the obstruction" which enjoined the defendants from any continuance or reconstruction of the obstruction. Because the intervening statute altered the underlying law such that the bridge was no longer an unlawful obstruction, we held that it was "quite plain the decree of the court cannot be enforced." Wheeling Bridge II, 59 U.S. at 431-32. The Court explained that had Wheeling Bridge I awarded money damages in an action at law, then that judgment would be final, and Congress' later action could not have affected plaintiff's right to those damages. See 59 U.S. at 431. But because the decree entered in Wheeling Bridge I provided for prospective relief a continuing injunction against the continuation or reconstruction of the bridge the ongoing validity of the injunctive relief depended on "whether or not [the bridge] interferes with the right of navigation." 59 U.S. at 431. When Congress altered the underlying law such that the bridge was no longer an unlawful obstruction, the injunction against the maintenance of the bridge was not enforceable. See id. at 432.

Applied here, the principles of Wheeling Bridge II demonstrate that the automatic stay of 3626(e)(2) does not unconstitutionally "suspend" or reopen a judgment of an Article III court. Section 3626(e)(2) does not by itself "tell judges when, how, or what to do." Instead, 3626(e)(2) merely reflects the change implemented by 3626(b), which does the "heavy lifting" in the statutory scheme by establishing new standards for prospective relief. The PLRA's automatic stay provision assists in the enforcement of 3626(b)(2) and (3) by requiring the court to stay any prospective relief that, due to the change in the underlying standard, is no longer enforceable, i.e., prospective relief that is not supported by the findings specified in 3626(b)(2) and (3).

By establishing new standards for the enforcement of prospective relief in 3626(b), Congress has altered the relevant underlying law. The PLRA has restricted courts' authority to issue and enforce prospective relief concerning prison conditions, requiring that such relief be supported by findings and precisely tailored to what is needed to remedy the violation of a federal right. We note that the constitutionality of 3626(b) is not challenged here; we assume, without deciding, that the new standards it pronounces are effective. As Plaut and Wheeling Bridge I instruct, when Congress changes the law underlying a judgment awarding prospective relief, that relief is no longer enforceable to the extent that it is inconsistent with the new law. Although the remedial injunction here is a "final judgment" for purposes of appeal, it is not the "last word of the judicial department." Plaut, 514 U.S. at 227. The provision of prospective relief is subject to the continuing supervisory jurisdiction of the court, and therefore may be altered according to subsequent changes in the law. Prospective relief must be "modified if, as it later turns out, one or more of the obligations placed upon the parties has become impermissible under federal law."

The entry of the automatic stay under 3626(e)(2) helps to implement the change in the law caused by 3626(b)(2) and (3). If the prospective relief under the existing decree is not supported by the findings required under 3626(b)(2), and the court has not made the findings required by 3626(b)(3), then prospective relief is no longer enforceable and must be stayed. The entry of the stay does not reopen or "suspend" the previous judgment, nor does it divest the court of authority to decide the merits of the termination motion. Rather, the stay merely reflects the changed legal circumstances that prospective relief under the existing decree is no longer enforceable, and remains unenforceable unless and until the court makes the findings required by 3626(b)(3).

For the same reasons, 3626(e)(2) does not violate the separation of powers principle articulated in United States v. Klein, 80 U.S. 128 (1872). In that case, Klein, the executor of the estate of a Confederate sympathizer, sought to recover the value of property seized by the United States during the Civil War, which by statute was recoverable if Klein could demonstrate that the decedent had not given aid or comfort to the rebellion. Id. at 131. In United States v. Padelford, 76 U.S. 531, 542-43 (1870), we held that a Presidential pardon satisfied the burden of proving that no such aid or comfort had been given. While Klein's case was pending, Congress enacted a statute providing that a pardon would instead be taken as proof that the pardoned individual had in fact aided the enemy, and if the claimant offered proof of a pardon the court must dismiss the case for lack of jurisdiction. Klein, 80 U.S. at 133-34. We concluded that the statute was unconstitutional because it purported to "prescribe rules of decision to the Judicial Department of the government in cases pending before it." Id. at 146.

Here, the prisoners argue that Congress has similarly prescribed a rule of decision because, for the period of time until the district court makes a final decision on the merits of the motion to terminate prospective relief, 3626(e)(2) mandates a particular outcome: the termination of prospective relief. As we noted in Plaut, however, "[w]hatever the precise scope of Klein, later decisions have made it clear that its prohibition does not take hold when Congress 'amend[s] applicable law.'" 514 U.S. at 218. The prisoners concede this point but contend that, because 3626(e)(2) does not itself amend the legal standard, Klein is still applicable. As we have explained, however, 3626(e)(2) must be read not in isolation, but in the context of 3626 as a whole. Rather than prescribing a rule of decision, 3626(e)(2) simply imposes the consequences of the court's application of the new legal standard.

Finally, the prisoners assert that, even if 3626(e)(2) does not fall within the recognized prohibitions of Hayburn's Case, Plaut, or Klein, it still offends the principles of separation of powers because it places a deadline on judicial decisionmaking, thereby interfering with core judicial functions. Congress' imposition of a time limit in 3626(e)(2), however, does not in itself offend the structural concerns underlying the Constitution's separation of powers. For example, if the PLRA granted courts 10 years to determine whether they could make the required findings, then certainly the PLRA would raise no apprehensions that Congress had encroached on the core function of the Judiciary to decide "cases and controversies properly before them." Respondents' concern with the time limit, then, must be its relative brevity. But whether the time is so short that it deprives litigants of a meaningful opportunity to be heard is a due process question, an issue that is not before us.

In contrast to due process, which principally serves to protect the personal rights of litigants to a full and fair hearing, separation of powers principles are primarily addressed to the structural concerns of protecting the role of the independent Judiciary within the constitutional design. In this action, we have no occasion to decide whether there could be a time constraint on judicial action that was so severe that it implicated these structural separation of powers concerns. The PLRA does not deprive courts of their adjudicatory role, but merely provides a new legal standard for relief and encourages courts to apply that standard promptly.

[W]e conclude that this provision does not violate separation of powers principles. Accordingly, the judgment of the Court of Appeals for the Seventh Circuit is reversed, and the action is remanded for further proceedings consistent with this opinion.

Justice Souter, with whom Justice Ginsberg joins, concurring in part and dissenting in part.

[Justices Souter and Ginsberg joined in the Court's opinion except for its discussion of whether the time limit contained within the statute raised a separation of powers concern.]

Justice Breyer, with whom Justice Stevens joins, dissenting.

[Justices Breyer and Stevens would have interpreted the statute differently so as to avoid constitutional issues.]

Consider the following matters in connection with Miller v. French:

1. What relief did the warden, Miller, seek and on what basis?

2. What argument did the prisoner, French, make in response that the federal court could not grant Miller's requested relief?

3. What prerogatives, according to the Court, does Article III and separation of powers preserve to the federal courts? From what sources are they drawn?

4. Why did the Court hold that the Prison Litigation Reform Act did not violate the rule derived from Plaut v. Spendthrift Farm, Inc.?

5. What three rules did Justice O'Connor identify that limited Congress' power to regulate the federal judiciary?

6. What does the Court view as the critical defect at issue in the cases regarding the statutory mechanism for administering pensions for disabled veterans of the Revolutionary War?

9. If Congress may change existing law and that law would be applicable to cases not yet finally adjudicated, what was the problem in United States v. Klein?