Greg Herrick, an antique aircraft enthusiast seeking to restore a vintage airplane manufactured by the Fairchild Engine and Airplane Corporation (FEAC), filed a Freedom of Information Act (FOIA) request asking the Federal Aviation Administration (FAA) for copies of technical documents related to the airplane. The FAA denied his request based on FOIA's exemption for trade secrets, see 5 U. S. C. sec.552(b)(4). Herrick took an administrative appeal, but when respondent Fairchild, FEAC's successor, objected to the documents' release, the FAA adhered to its original decision. Herrick then filed an unsuccessful FOIA lawsuit to secure the documents. Less than a month after that suit was resolved, petitioner Taylor, Herrick's friend and an antique aircraft enthusiast himself, made a FOIA request for the same documents Herrick had unsuccessfully sued to obtain. When the FAA failed to respond, Taylor filed suit in the U. S. District Court for the District of Columbia. Holding the suit barred by claim preclusion, the District Court granted summary judgment to the FAA and to Fairchild, as intervenor in Taylor's action. The court acknowledged that Taylor was not a party to Herrick's suit, but held that a nonparty may be bound by a judgment if she was "virtually represented" by a party. The D. C. Circuit affirmed, announcing a five-factor test for "virtual representation." The first two factors of the D. C. Circuit's test--"identity of interests" and "adequate representation"--are necessary but not sufficient for virtual representation. In addition, at least one of three other factors must be established: "a close relationship between the present party and his putative representative," "substantial participation by the present party in the first case," or "tactical maneuvering on the part of the present party to avoid preclusion by the prior judgment." The D. C. Circuit acknowledged the absence of any indication that Taylor participated in, or even had notice of, Herrick's suit. It nonetheless found the "identity of interests," "adequate representation," and "close relationship" factors satisfied because the two men sought release of the same documents, were "close associates," had discussed working together to restore Herrick's plane, and had used the same lawyer to pursue their suits. Because these conditions sufficed to establish virtual representation, the court left open the question whether Taylor had engaged in tactical maneuvering to avoid preclusion.

Held:

1. The theory of preclusion by "virtual representation" is disapproved. The preclusive effects of a judgment in a federal-question case decided by a federal court should instead be determined according to the established grounds for nonparty preclusion. Pp. 9-21.

(a) The preclusive effect of a federal-court judgment is determined by federal common law, subject to due process limitations. Pp. 9-13.

(1) Extending the preclusive effect of a judgment to a nonparty runs up against the "deep-rooted historic tradition that everyone should have his own day in court." Richards v. Jefferson County, 517 U. S. 793 (internal quotation marks omitted). Indicating the strength of that tradition, this Court has often repeated the general rule that "one is not bound by a judgment in personam in a litigation in which he is not designated a party or to which he has not been made a party by service of process." Hansberry v. Lee, 311 U. S. 32 . Pp. 9-10.

(2) The rule against nonparty preclusion is subject to exceptions, grouped for present purposes into six categories. First, "[a] person who agrees to be bound by the determination of issues in an action between others is bound in accordance with the [agreement's] terms." Restatement (Second) of Judgments sec.40. Second, nonparty preclusion may be based on a pre-existing substantive legal relationship between the person to be bound and a party to the judgment, e.g., assignee and assignor. Third, "in certain limited circumstances," a nonparty may be bound by a judgment because she was " 'adequately represented by someone with the same interests who [wa]s a party' " to the suit. Richards, 517 U. S., at 798. Fourth, a nonparty is bound by a judgment if she "assume[d] control" over the litigation in which that judgment was rendered. Montana v. United States, 440 U. S. 147 . Fifth, a party bound by a judgment may not avoid its preclusive force by relitigating through a proxy. Preclusion is thus in order when a person who did not participate in litigation later brings suit as the designated representative or agent of a person who was a party to the prior adjudication. Sixth, a special statutory scheme otherwise consistent with due process--e.g., bankruptcy proceedings--may "expressly foreclos[e] successive litigation by nonlitigants." Martin v. Wilks, 490 U. S. 755 , n. 2. Pp. 10-13.

(b) Reaching beyond these six categories, the D. C. Circuit recognized a broad "virtual representation" exception to the rule against nonparty preclusion. None of the arguments advanced by that court, the FAA, or Fairchild justify such an expansive doctrine. Pp. 13-22.

(1) The D. C. Circuit purported to ground its doctrine in this Court's statements that, in some circumstances, a person may be bound by a judgment if she was adequately represented by a party to the proceeding yielding that judgment. But the D. C. Circuit's definition of "adequate representation" strayed from the meaning this Court has attributed to that term. In Richards, the Alabama Supreme Court had held a tax challenge barred by a judgment upholding the same tax in a suit by different taxpayers. 517 U. S., at 795-797. This Court reversed, holding that nonparty preclusion was inconsistent with due process where there was no showing (1) that the court in the first suit "took care to protect the interests" of absent parties, or (2) that the parties to the first litigation "understood their suit to be on behalf of absent [parties]," id., at 802. In holding that representation can be "adequate" for purposes of nonparty preclusion even where these two factors are absent, the D. C. Circuit misapprehended Richards. Pp. 14-15.

(2) Fairchild and the FAA ask this Court to abandon altogether the attempt to delineate discrete grounds and clear rules for nonparty preclusion. Instead, they contend, only an equitable and heavily fact-driven inquiry can account for all of the situations in which nonparty preclusion is appropriate. This argument is rejected. First, respondents' balancing test is at odds with the constrained approach advanced by this Court's decisions, which have endeavored to delineate discrete, limited exceptions to the fundamental rule that a litigant is not bound by a judgment to which she was not a party, see, e.g., Richards, 517 U. S., at 798-799. Second, a party's representation of a nonparty is "adequate" for preclusion purposes only if, at a minimum: (1) the interests of the nonparty and her representative are aligned, see Hansberry, 311 U. S., at 43, and (2) either the party understood herself to be acting in a representative capacity or the original court took care to protect the nonparty's interests, see Richards, 517 U. S., at 801-802. Adequate representation may also require (3) notice of the original suit to the persons alleged to have been represented. See id., at 801. In the class-action context, these limitations are implemented by Federal Rule of Civil Procedure 23's procedural safeguards. But an expansive virtual representation doctrine would recognize a common-law kind of class action shorn of these protections. Third, a diffuse balancing approach to nonparty preclusion would likelycomplicate the task of district courts faced in the first instance with preclusion questions. Pp. 15-19.

(3) Finally, the FAA contends that nonparty preclusion should apply more broadly in "public-law" litigation than in "private-law" controversies. First, the FAA points to Richards' acknowledgment that when a taxpayer challenges "an alleged misuse of public funds" or "other public action," the suit "has only an indirect impact on [the plaintiff's] interests," 517 U. S., at 803, and "the States have wide latitude to establish procedures [limiting] the number of judicial proceedings that may be entertained," ibid. In contrast to the public-law litigation contemplated in Richards, however, a successful FOIA action results in a grant of relief to the individual plaintiff, not a decree benefiting the public at large. Furthermore, Richards said only that, for the type of public-law claims there envisioned, States were free to adopt procedures limiting repetitive litigation. While it appears equally evident that Congress can adopt such procedures, it hardly follows that this Court should proscribe or confine successive FOIA suits by different requesters. Second, the FAA argues that, because the number of plaintiffs in public-law cases is potentially limitless, it is theoretically possible for several persons to coordinate a series of vexatious repetitive lawsuits. But this risk does not justify departing from the usual nonparty preclusion rules. Stare decisis will allow courts to dispose of repetitive suits in the same circuit, and even when stare decisis is not dispositive, the human inclination not to waste money should discourage suits based on claims or issues already decided. Pp. 19-22.

2. The remaining question is whether the result reached by the courts below can be justified based on one of the six the established grounds for nonparty preclusion. With one exception, those grounds plainly have no application here. Respondents argue that Taylor's suit is a collusive attempt to relitigate Herrick's claim. That argument justifies a remand to allow the courts below the opportunity to determine whether the fifth ground for nonparty preclusion--preclusion because a nonparty to earlier litigation has brought suit as an agent of a party bound by the prior adjudication--applies to Taylor's suit. But courts should be cautious about finding preclusion on the basis of agency. A mere whiff of "tactical maneuvering" will not suffice; instead, principles of agency law indicate that preclusion is appropriate only if the putative agent's conduct of the suit is subject to the control of the party who is bound by the prior adjudication. Finally, the Court rejects Fairchild's suggestion that Taylor must bear the burden of proving he is not acting as Herrick's agent. Claim preclusion is an affirmative defense for the defendant to plead and prove. Pp. 22-25.

490 F. 3d 965, vacated and remanded.

Ginsburg, J., delivered the opinion for a unanimous Court.

In the Authorization for Use of Military Force (AUMF), Congress empowered the President "to use all necessary and appropriate force against those ... he determines planned, authorized, committed, or aided the terrorist attacks ... on September 11, 2001." In Hamdi v. Rumsfeld, 542 U. S. 507 , five Justices recognized that detaining individuals captured while fighting against the United States in Afghanistan for the duration of that conflict was a fundamental and accepted incident to war. Thereafter, the Defense Department established Combatant Status Review Tribunals (CSRTs) to determine whether individuals detained at the U. S. Naval Station at Guantanamo Bay, Cuba, were "enemy combatants."

Petitioners are aliens detained at Guantanamo after being captured in Afghanistan or elsewhere abroad and designated enemy combatants by CSRTs. Denying membership in the al Qaeda terrorist network that carried out the September 11 attacks and the Taliban regime that supported al Qaeda, each petitioner sought a writ of habeas corpus in the District Court, which ordered the cases dismissed for lack of jurisdiction because Guantanamo is outside sovereign U. S. territory. The D. C. Circuit affirmed, but this Court reversed, holding that 28 U. S. C. sec.2241 extended statutory habeas jurisdiction to Guantanamo. See Rasul v. Bush, 542 U. S. 466 . Petitioners' cases were then consolidated into two proceedings. In the first, the district judge granted the Government's motion to dismiss, holding that the detainees had no rights that could be vindicated in a habeas action. In the second, the judge held that the detainees had due process rights.

While appeals were pending, Congress passed the Detainee Treatment Act of 2005 (DTA), sec.1005(e) of which amended 28 U. S. C. sec.2241 to provide that "no court, justice, or judge shall have jurisdiction to ... consider ... an application for ... habeas corpus filed by or on behalf of an alien detained ... at Guantanamo," and gave the D. C. Court of Appeals "exclusive" jurisdiction to review CSRT decisions. In Hamdan v. Rumsfeld, 548 U. S. 557 , the Court held this provision inapplicable to cases (like petitioners') pending when the DTA was enacted. Congress responded with the Military Commissions Act of 2006 (MCA), sec.7(a) of which amended sec.2241(e)(1) to deny jurisdiction with respect to habeas actions by detained aliens determined to be enemy combatants, while sec.2241(e)(2) denies jurisdiction as to "any other action against the United States ... relating to any aspect of the detention, transfer, treatment, trial, or conditions of confinement" of a detained alien determined to be an enemy combatant. MCA sec.7(b) provides that the 2241(e) amendments "shall take effect on the date of the enactment of this Act, and shall apply to all cases, without exception, pending on or after [that] date ... which relate to any aspect of the detention, transfer, treatment, trial, or conditions of detention of an alien detained ... since September 11, 2001."

The D. C. Court of Appeals concluded that MCA sec.7 must be read to strip from it, and all federal courts, jurisdiction to consider petitioners' habeas applications; that petitioners are not entitled to habeas or the protections of the Suspension Clause, U. S. Const., Art. I, sec.9, cl. 2, which provides that "[t]he Privilege of the Writ of Habeas Corpus shall not be suspended, unless when in Cases of Rebellion or Invasion the public Safety may require it"; and that it was therefore unnecessary to consider whether the DTA provided an adequate and effective substitute for habeas.

Held:

1. MCA sec.7 denies the federal courts jurisdiction to hear habeas actions, like the instant cases, that were pending at the time of its enactment. Section sec.7(b)'s effective date provision undoubtedly applies to habeas actions, which, by definition, "relate to ... detention" within that section's meaning. Petitioners argue to no avail that sec.7(b) does not apply to a sec.2241(e)(1) habeas action, but only to "any other action" under sec.2241(e)(2), because it largely repeats that section's language. The phrase "other action" in sec.2241(e)(2) cannot be understood without referring back to sec.2241(e)(1), which explicitly mentions the "writ of habeas corpus." Because the two paragraphs' structure implies that habeas is a type of action "relating to any aspect of ... detention," etc., pending habeas actions are in the category of cases subject to the statute's jurisdictional bar. This is confirmed by the MCA's legislative history. Thus, if MCA sec.7 is valid, petitioners' cases must be dismissed. Pp. 5-8.

2. Petitioners have the constitutional privilege of habeas corpus. They are not barred from seeking the writ or invoking the Suspension Clause's protections because they have been designated as enemy combatants or because of their presence at Guantanamo. Pp. 8-41.

(a) A brief account of the writ's history and origins shows that protection for the habeas privilege was one of the few safeguards of liberty specified in a Constitution that, at the outset, had no Bill of Rights; in the system the Framers conceived, the writ has a centrality that must inform proper interpretation of the Suspension Clause. That the Framers considered the writ a vital instrument for the protection of individual liberty is evident from the care taken in the Suspension Clause to specify the limited grounds for its suspension: The writ may be suspended only when public safety requires it in times of rebellion or invasion. The Clause is designed to protect against cyclical abuses of the writ by the Executive and Legislative Branches. It protects detainee rights by a means consistent with the Constitution's essential design, ensuring that, except during periods of formal suspension, the Judiciary will have a time-tested device, the writ, to maintain the "delicate balance of governance." Hamdi, supra, at 536. Separation-of-powers principles, and the history that influenced their design, inform the Clause's reach and purpose. Pp. 8-15.

(b) A diligent search of founding-era precedents and legal commentaries reveals no certain conclusions. None of the cases the parties cite reveal whether a common-law court would have granted, or refused to hear for lack of jurisdiction, a habeas petition by a prisoner deemed an enemy combatant, under a standard like the Defense Department's in these cases, and when held in a territory, like Guantanamo, over which the Government has total military and civil control. The evidence as to the writ's geographic scope at common law is informative, but, again, not dispositive. Petitioners argue that the site of their detention is analogous to two territories outside England to which the common-law writ ran, the exempt jurisdictions and India, but critical differences between these places and Guantanamo render these claims unpersuasive. The Government argues that Guantanamo is more closely analogous to Scotland and Hanover, where the writ did not run, but it is unclear whether the common-law courts lacked the power to issue the writ there, or whether they refrained from doing so for prudential reasons. The parties' arguments that the very lack of a precedent on point supports their respective positions are premised upon the doubtful assumptions that the historical record is complete and that the common law, if properly understood, yields a definite answer to the questions before the Court. Pp. 15-22.

(c) The Suspension Clause has full effect at Guantanamo. The Government's argument that the Clause affords petitioners no rights because the United States does not claim sovereignty over the naval station is rejected. Pp. 22-42.

(i) The Court does not question the Government's position that Cuba maintains sovereignty, in the legal and technical sense, over Guantanamo, but it does not accept the Government's premise that de jure sovereignty is the touchstone of habeas jurisdiction. Common-law habeas' history provides scant support for this proposition, and it is inconsistent with the Court's precedents and contrary to fundamental separation-of-powers principles. Pp. 22-25.

(ii) Discussions of the Constitution's extraterritorial application in cases involving provisions other than the Suspension Clause undermine the Government's argument. Fundamental questions regarding the Constitution's geographic scope first arose when the Nation acquired Hawaii and the noncontiguous Territories ceded by Spain after the Spanish-American War, and Congress discontinued its prior practice of extending constitutional rights to territories by statute. In the so-called Insular Cases, the Court held that the Constitution had independent force in the territories that was not contingent upon acts of legislative grace. See, e.g., Dorr v. United States, 195 U. S. 138 . Yet because of the difficulties and disruption inherent in transforming the former Spanish colonies' civil-law system into an Anglo-American system, the Court adopted the doctrine of territorial incorporation, under which the Constitution applies in full in incorporated Territories surely destined for statehood but only in part in unincorporated Territories. See, e.g., id., at 143. Practical considerations likewise influenced the Court's analysis in Reid v. Covert, 354 U. S. 1 , where, in applying the jury provisions of the Fifth and Sixth Amendments to American civilians being tried by the U. S. military abroad, both the plurality and the concurrences noted the relevance of practical considerations, related not to the petitioners' citizenship, but to the place of their confinement and trial. Finally, in holdingthat habeas jurisdiction did not extend to enemy aliens, convicted of violating the laws of war, who were detained in a German prison during the Allied Powers' post-World War II occupation, the Court, in Johnson v. Eisentrager, 339 U. S. 763 , stressed the practical difficulties of ordering the production of the prisoners, id., at 779. The Government's reading of Eisentrager as adopting a formalistic test for determining the Suspension Clause's reach is rejected because: (1) the discussion of practical considerations in that case was integral to a part of the Court's opinion that came before it announced its holding, see id., at 781; (2) it mentioned the concept of territorial sovereignty only twice in its opinion, in contrast to its significant discussion of practical barriers to the running of the writ; and (3) if the Government's reading were correct, the opinion would have marked not only a change in, but a complete repudiation of, the Insular Cases' (and later Reid's) functional approach. A constricted reading of Eisentrager overlooks what the Court sees as a common thread uniting all these cases: The idea that extraterritoriality questions turn on objective factors and practical concerns, not formalism. Pp. 25-34.

(iii) The Government's sovereignty-based test raises troubling separation-of-powers concerns, which are illustrated by Guantanamo's political history. Although the United States has maintained complete and uninterrupted control of Guantanamo for over 100 years, the Government's view is that the Constitution has no effect there, at least as to noncitizens, because the United States disclaimed formal sovereignty in its 1903 lease with Cuba. The Nation's basic charter cannot be contracted away like this. The Constitution grants Congress and the President the power to acquire, dispose of, and govern territory, not the power to decide when and where its terms apply. To hold that the political branches may switch the Constitution on or off at will would lead to a regime in which they, not this Court, say "what the law is." Marbury v. Madison, 1 Cranch 137, 177. These concerns have particular bearing upon the Suspension Clause question here, for the habeas writ is itself an indispensable mechanism for monitoring the separation of powers. Pp. 34-36.

(iv) Based on Eisentrager, supra, at 777, and the Court's reasoning in its other extraterritoriality opinions, at least three factors are relevant in determining the Suspension Clause's reach: (1) the detainees' citizenship and status and the adequacy of the process through which that status was determined; (2) the nature of the sites where apprehension and then detention took place; and (3) the practical obstacles inherent in resolving the prisoner's entitlement to the writ. Application of this framework reveals, first, that petitioners' status is in dispute: They are not American citizens, but deny they are enemy combatants; and although they have been afforded some process in CSRT proceedings, there has been no Eisentrager-style trial by military commission for violations of the laws of war. Second, while the sites of petitioners' apprehension and detention weigh against finding they have Suspension Clause rights, there are critical differences between Eisentrager's German prison, circa 1950, and the Guantanamo Naval Station in 2008, given the Government's absolute and indefinite control over the naval station. Third, although the Court is sensitive to the financial and administrative costs of holding the Suspension Clause applicable in a case of military detention abroad, these factors are not dispositive because the Government presents no credible arguments that the military mission at Guantanamo would be compromised if habeas courts had jurisdiction. The situation in Eisentrager was far different, given the historical context and nature of the military's mission in post-War Germany. Pp. 36-41.

(d) Petitioners are therefore entitled to the habeas privilege, and if that privilege is to be denied them, Congress must act in accordance with the Suspension Clause's requirements. Cf. Rasul, 542 U. S., at 564. Pp. 41-42.

3. Because the DTA's procedures for reviewing detainees' status are not an adequate and effective substitute for the habeas writ, MCA sec.7 operates as an unconstitutional suspension of the writ. Pp. 42-64.

(a) Given its holding that the writ does not run to petitioners, the D. C. Circuit found it unnecessary to consider whether there was an adequate substitute for habeas. This Court usually remands for consideration of questions not decided below, but departure from this rule is appropriate in "exceptional" circumstances, see, e.g., Cooper Industries, Inc. v. Aviall Services, Inc., 543 U. S. 157 , here, the grave separation-of-powers issues raised by these cases and the fact that petitioners have been denied meaningful access to a judicial forum for years. Pp. 42-44.

(b) Historically, Congress has taken care to avoid suspensions of the writ. For example, the statutes at issue in the Court's two leading cases addressing habeas substitutes, Swain v. Pressley, 430 U. S. 372 , and United States v. Hayman, 342 U. S. 205 , were attempts to streamline habeas relief, not to cut it back. Those cases provide little guidance here because, inter alia, the statutes in question gave the courts broad remedial powers to secure the historic office of the writ, and included saving clauses to preserve habeas review as an avenue of last resort. In contrast, Congress intended the DTA and the MCA to circumscribe habeas review, as is evident from the unequivocal nature of MCA sec.7's jurisdiction-stripping language, from the DTA's text limiting the Court of Appeals' jurisdiction to assessing whether the CSRT complied with the "standards and procedures specified by the Secretary of Defense," DTA sec.1005(e)(2)(C), and from the absence of a saving clause in either Act. That Congress intended to create a more limited procedure is also confirmed by the legislative history and by a comparison of the DTA and the habeas statute that would govern in MCA sec.7's absence, 28 U. S. C. sec.2241. In sec.2241, Congress authorized "any justice" or "circuit judge" to issue the writ, thereby accommodating the necessity for factfinding that will arise in some cases by allowing the appellate judge or Justice to transfer the case to a district court. See sec.2241(b). However, by granting the D. C. Circuit "exclusive" jurisdiction over petitioners' cases, see DTA sec.1005(e)(2)(A), Congress has foreclosed that option in these cases. Pp. 44-49.

(c) This Court does not endeavor to offer a comprehensive summary of the requisites for an adequate habeas substitute. It is uncontroversial, however, that the habeas privilege entitles the prisoner to a meaningful opportunity to demonstrate that he is being held pursuant to "the erroneous application or interpretation" of relevant law, INS v. St. Cyr, 533 U. S. 289 , and the habeas court must have the power to order the conditional release of an individual unlawfully detained. But more may be required depending on the circumstances. Petitioners identify what they see as myriad deficiencies in the CSRTs, the most relevant being the constraints upon the detainee's ability to rebut the factual basis for the Government's assertion that he is an enemy combatant. At the CSRT stage the detainee has limited means to find or present evidence to challenge the Government's case, does not have the assistance of counsel, and may not be aware of the most critical allegations that the Government relied upon to order his detention. His opportunity to confront witnesses is likely to be more theoretical than real, given that there are no limits on the admission of hearsay. The Court therefore agrees with petitioners that there is considerable risk of error in the tribunal's findings of fact. And given that the consequence of error may be detention for the duration of hostilities that may last a generation or more, the risk is too significant to ignore. Accordingly, for the habeas writ, or its substitute, to function as an effective and meaningful remedy in this context, the court conducting the collateral proceeding must have some ability to correct any errors, to assess the sufficiency of the Government's evidence, and to admit and consider relevant exculpatory evidence that was not introduced during the earlier proceeding. In re Yamashita, 327 U. S. 1 , and Ex parte Quirin, 317 U. S. 1 , distinguished. Pp. 49-57.

(d) Petitioners have met their burden of establishing that the DTA review process is, on its face, an inadequate substitute for habeas. Among the constitutional infirmities from which the DTA potentially suffers are the absence of provisions allowing petitioners to challenge the President's authority under the AUMF to detain them indefinitely, to contest the CSRT's findings of fact, to supplement the record on review with exculpatory evidence discovered after the CSRT proceedings, and to request release. The statute cannot be read to contain each of these constitutionally required procedures. MCA sec.7 thus effects an unconstitutional suspension of the writ. There is no jurisdictional bar to the District Court's entertaining petitioners' claims. Pp. 57-64.

4. Nor are there prudential barriers to habeas review. Pp. 64-70.

(a) Petitioners need not seek review of their CSRT determinations in the D. C. Circuit before proceeding with their habeas actions in the District Court. If these cases involved detainees held for only a short time while awaiting their CSRT determinations, or were it probable that the Court of Appeals could complete a prompt review of their applications, the case for requiring temporary abstention or exhaustion of alternative remedies would be much stronger. But these qualifications no longer pertain here. In some instances six years have elapsed without the judicial oversight that habeas corpus or an adequate substitute demands. To require these detainees to pursue the limited structure of DTA review before proceeding with habeas actions would be to require additional months, if not years, of delay. This holding should not be read to imply that a habeas court should intervene the moment an enemy combatant steps foot in a territory where the writ runs. Except in cases of undue delay, such as the present, federal courts should refrain from entertaining an enemy combatant's habeas petition at least until after the CSRT has had a chance to review his status. Pp. 64-67.

(b) In effectuating today's holding, certain accommodations--including channeling future cases to a single district court and requiring that court to use its discretion to accommodate to the greatest extent possible the Government's legitimate interest in protecting sources and intelligence gathering methods--should be made to reduce the burden habeas proceedings will place on the military, without impermissibly diluting the writ's protections. Pp. 67-68.

5. In considering both the procedural and substantive standards used to impose detention to prevent acts of terrorism, the courts must accord proper deference to the political branches. However, security subsists, too, in fidelity to freedom's first principles, chief among them being freedom from arbitrary and unlawful restraint and the personal liberty that is secured by adherence to the separation of powers. Pp. 68-70.

476 F. 3d 981, reversed and remanded.

Kennedy, J., delivered the opinion of the Court, in which Stevens, Souter, Ginsburg, and Breyer, JJ., joined. Souter, J., filed a concurring opinion, in which Ginsburg and Breyer, JJ., joined. Roberts, C. J., filed a dissenting opinion, in which Scalia, Thomas, and Alito, JJ., joined. Scalia, J., filed a dissenting opinion, in which Roberts, C. J., and Thomas and Alito, JJ., joined.

Notes:
*

* Together with No. 06-1196, Al Odah, Next Friend of Al Odah, et al. v. United States et al., also on certiorari to the same court.

A class action by and for human rights victims (Pimentel class) of Ferdinand Marcos, while he was President of the Republic of the Philippines (Republic), led to a nearly $2 billion judgment in a United States District Court. The Pimentel class then sought to attach the assets of Arelma, S. A. (Arelma), a company incorporated by Marcos, held by a New York broker (Merrill Lynch). The Republic and a Philippine commission (Commission) established to recover property wrongfully taken by Marcos are also attempting to recover this and other Marcos property. The Philippine National Banc (PNB) holds some of the disputed assets in escrow, awaiting the outcome of pending litigation in the Sandiganbayan, a Philippine court determining whether Marcos' property should be forfeited to the Republic. Facing claims from various Marcos creditors, including the Pimentel class, Merrill Lynch filed this interpleader action under 28 U. S. C. sec.1335, naming, among the defendants, the Republic, the Commission, Arelma, PNB (all petitioners here), and the Pimentel class (respondents here). The Republic and the Commission asserted sovereign immunity under the Foreign Sovereign Immunities Act of 1976, and moved to dismiss pursuant to Federal Rule of Civil Procedure 19(b), arguing that the action could not proceed without them. Arelma and PNB also sought a Rule 19(b) dismissal. The District Court refused, but the Ninth Circuit reversed, holding that the Republic and the Commission are entitled to sovereign immunity and are required parties under Rule 19(a), and it entered a stay pending the Sandiganbayan litigation's outcome. Finding that that litigation could not determine entitlement to Arelma's assets, the District Court vacated the stay and ultimately awarded the assets to the Pimentel class. The Ninth Circuit affirmed, holding that dismissal was not warranted under Rule 19(b) because, though the Republic and the Commission were required parties, their claim had so little likelihood of success on the merits that the action could proceed without them. The court found it unnecessary to consider whether prejudice to those entities might be lessened by a judgment or interim decree in the interpleader action, found the entities' failure to obtain a judgment in the Sandiganbayan an equitable consideration counseling against dismissing the interpleader suit, and found that allowing the interpleader case to proceed would serve the Pimentel class' interests.

Held:

1. Because Arelma and PNB also seek review of the Ninth Circuit's decision, this Court need not rule on the question whether the Republic and the Commission, having been dismissed from the suit, had the right to seek review of the decision that the suit could proceed in their absence. As a general matter any party may move to dismiss an action under Rule 19(b). Arelma and PNB have not lost standing to have the judgment vacated in its entirety on procedural grounds simply because they did not appeal, or petition for certiorari on, the underlying merits ruling denying them the interpleaded assets. Pp. 7-9.

2. Rule 19 requires dismissal of the interpleader action. Pp. 9-20.

(a) Under Rule 19(a), nonjoinder even of a required person does not always result in dismissal. When joinder is not feasible, the question whether an action should proceed turns on nonexclusive considerations in Rule 19(b), which asks whether "in equity and good conscience, the action should proceed among the existing parties or should be dismissed." The joinder issue can be complex, and the case-specific determinations involve multiple factors, some "substantive, some procedural, some compelling by themselves, and some subject to balancing against opposing interests," Provident Tradesmens Bank & Trust Co. v. Patterson, 390 U. S. 102 . Pp. 9-10.

(b) Here, Rule 19(a)'s application is not contested: The Republic and the Commission are required entities. And this Court need not decide the proper standard of review for Rule 19(b) decisions, because the Ninth Circuit's errors of law require reversal. Pp. 10-19.

(1) The first factor directs the court to consider, in determining whether the action may proceed, the prejudice to absent entities and present parties in the event judgment is rendered without joinder. Rule 19(b)(1). The Ninth Circuit gave insufficient weight to the sovereign status of the Republic and the Commission in considering whether they would be prejudiced if the case proceeded. Giving full effect to sovereign immunity promotes the comity and dignity interests that contributed to the development of the immunity doctrine. See, e.g., Verlinden B. V. v. Central Bank of Nigeria, 461 U. S. 480 . These interests are concrete here. The entities' claims arise from historically and politically significant events for the Republic and its people, and the entities have a unique interest in resolving matters related to Arelma's assets. A foreign state has a comity interest in using its courts for a dispute if it has a right to do so. Its dignity is not enhanced if other nations bypass its courts without right or good cause. A more specific affront could result if property the Republic and the Commission claim is seized by a foreign court decree. This Court has not considered the precise question presented, but authorities involving the intersection of joinder and the United States' governmental immunity, see, e.g., Mine Safety Appliances Co. v. Forrestal, 326 U. S. 371 , instruct that where sovereign immunity is asserted, and the sovereign's claims are not frivolous, dismissal must be ordered where there is a potential for injury to the absent sovereign's interests. The claims of the Republic and the Commission were not frivolous, and the Ninth Circuit thus erred in ruling on their merits. The privilege of sovereign immunity from suit is much diminished if an important and consequential ruling affecting the sovereign's substantial interest is determined, or at least assumed, by a federal court in its absence and over its objection. The Pimentel class' interest in recovering its damages is not discounted, but important comity concerns are implicated by assertion of foreign sovereign immunity. The error is not that the courts below gave too much weight to the Pimentel class' interests, but that they did not accord proper weight to the compelling sovereign immunity claim. Pp. 11-16.

(2) The second factor is the extent to which any prejudice could be lessened or avoided by relief or measures alternative to dismissal, Rule 19(b)(2), but no alternative remedies or forms of relief have been proposed or appear to be available. As to the third factor--whether a judgment rendered without the absent party would be adequate, Rule 19(b)(3)--"adequacy" refers not to satisfaction of the Pimentel class' claims, but to the "public stake in settling disputes by wholes, whenever possible," Provident Bank, supra, at 111. Going forward with the action in the absence of the Republic and the Commission would not further this public interest because they could not be bound by a judgment to which they were not parties. As to the fourth factor--whether the plaintiff would have an adequate remedy if the action were dismissed for nonjoinder, Rule 19(b)(4)--the Ninth Circuit made much of the tort victims' lack of an alternative forum. But Merrill Lynch, not the Pimentel class, is the plaintiff as the stakeholder in the interpleader action. See 28 U. S. C. sec.1335(a). The Pimentel class' interests are not irrelevant to Rule 19(b)'s equitable balance, but the Rule's other provisions are the relevant ones to consult. A dismissal on the ground of nonjoinder will not provide Merrill Lynch with a judgment determining entitlement to the assets so it could be done with the matter, but it likely would give Merrill Lynch an effective defense against piecemeal litigation by various claimants and inconsistent, conflicting judgments. Any prejudice to Merrill Lynch is outweighed by prejudice to the absent entities invoking sovereign immunity. In the usual course, the Ninth Circuit's failure to give sufficient weight to the likely prejudice to the Republic and the Commission would warrant reversal and remand for further determinations, but here, that error plus this Court's analysis under Rule 19(b)'s additional provisions require the action's dismissal. Pp. 17-20.

464 F. 3d 885, reversed and remanded.

Kennedy, J., delivered the opinion of the Court, in which Roberts, C. J., and Scalia, Thomas, Ginsburg, Breyer, and Alito, JJ., joined, in which Souter, J., joined as to all but Parts IV-B and V,and in which Stevens, J., joined as to Part II. Stevens, J., and Souter, J., filed opinions concurring in part and dissenting in part.

The Multinational Force-Iraq (MNF-I) is an international coalition force composed of 26 nations, including the United States. It operates in Iraq under the unified command of U. S. military officers, at the Iraqi Government's request, and in accordance with United Nations Security Council Resolutions. Pursuant to the U. N. mandate, MNF-I forces detain individuals alleged to have committed hostile or warlike acts in Iraq, pending investigation and prosecution in Iraqi courts under Iraqi law.

Shawqi Omar and Mohammad Munaf (hereinafter petitioners) are American citizens who voluntarily traveled to Iraq and allegedly committed crimes there. They were each captured by military forces operating as part of the MNF-I; given hearings before MNF-I Tribunals composed of American officers, who concluded that petitioners posed threats to Iraq's security; and placed in the custody of the U. S. military operating as part of the MNF-I. Family members filed next-friend habeas corpus petitions on behalf of both petitioners in the United States District Court for the District of Columbia.

In Omar's case, after the Department of Justice informed Omar that the MNF-I had decided to refer him to the Central Criminal Court of Iraq for criminal proceedings, his attorney sought and obtained a preliminary injunction from the District Court barring Omar's removal from United States or MNF-I custody. Affirming, the D. C. Circuit first upheld the District Court's exercise of habeas jurisdiction, finding that Hirota v. MacArthur, 338 U. S. 197 , did not preclude review because Omar, unlike the habeas petitioners in Hirota, had yet to be convicted by a foreign tribunal.

Meanwhile, the District Court in Munaf's case dismissed his habeas petition for lack of jurisdiction. The court concluded that Hirota controlled and required that the petition be dismissed for lack of jurisdiction because the American forces holding Munaf were operating as part of an international force--the MNF-I. The D. C. Circuit agreed and affirmed. It distinguished its prior decision in Omar, which upheld jurisdiction over Omar's habeas petition, on the grounds that Munaf had been convicted by a foreign tribunal while Omar had not.

Held:

1. The habeas statute extends to American citizens held overseas by American forces operating subject to an American chain of command. The Government's argument that the federal courts lack jurisdiction over the detainees' habeas petitions in such circumstances because the American forces holding Omar and Munaf operate as part of a multinational force is rejected. The habeas statute, 28 U. S. C. sec.2241(c)(1), applies to persons held "in custody under or by color of the authority of the United States." The disjunctive "or" in sec.2241(c)(1) makes clear that actual Government custody suffices for jurisdiction, even if that custody could be viewed as "under ... color of" another authority, such as the MNF-I.

The Court also rejects the Government's contention that the District Court lacks jurisdiction in these cases because the multinational character of the MNF-I, like the multinational character of the tribunal at issue in Hirota, means that the MNF-I is not a United States entity subject to habeas. The present cases differ from Hirota in several respects. The Court in Hirota may have found it significant, in considering the nature of the tribunal established by General MacArthur, that in that case the Government argued that General MacArthur was not subject to United States authority, that his duty was to obey the Far Eastern Commission and not the U. S. War Department, and that no process this Court could issue would have any effect on his action. Here, in contrast, the Government acknowledges that U. S. military commanders answer to the President. These cases also differ from Hirota in that they concern American citizens, and the Court has indicated that habeas jurisdiction can depend on citizenship. See e.g., Johnson v. Eisentrager, 339 U. S. 763 . Pp. 7-11.

2. Federal district courts, however, may not exercise their habeas jurisdiction to enjoin the United States from transferring individuals alleged to have committed crimes and detained within the territory of a foreign sovereign to that sovereign for criminal prosecution. Because petitioners state no claim in their habeas petitions for which relief can be granted, their habeas petitions should have been promptly dismissed, and no injunction should have been entered. Pp. 11-28.

(a) The District Court abused its discretion in granting Omar a preliminary injunction, which the D. C. Circuit interpreted as prohibiting the Government from (1) transferring Omar to Iraqi custody, (2) sharing with the Iraqi Government details concerning any decision to release him, and (3) presenting him to the Iraqi courts for investigation and prosecution, without even considering the merits of the habeas petition. A preliminary injunction is an "extraordinary and drastic remedy." It should never be awarded as of right, Yakus v. United States, 321 U. S. 414 , and requires a demonstration of, inter alia, "a likelihood of success on the merits," Gonzales v. O Centro Esprita Beneficente Unio do Vegetal, 546 U. S. 418 . But neither the District Court nor the D. C. Circuit considered the likelihood of success as to the merits of Omar's habeas petition. Instead, the lower courts concluded that the "jurisdictional issues" implicated by Omar's petition presented difficult and substantial questions. A difficult question as to jurisdiction is, of course, no reason to grant a preliminary injunction.

The foregoing analysis would require reversal and remand in each of these cases: The lower courts in Munaf erred in dismissing for want of jurisdiction, and the lower courts in Omar erred in issuing and upholding the preliminary injunction. Our review of a preliminary injunction, however, "is not confined to the act of granting the injunctio[n]." City and County of Denver v. New York Trust Co., 229 U. S. 123 . Rather, a reviewing court has the power on appeal from an interlocutory order "to examine the merits of the case ... and upon deciding them in favor of the defendant to dismiss the bill." North Carolina R. Co. v. Story, 268 U. S. 288 . In short, there are occasions when it is appropriate for a court reviewing a preliminary injunction to proceed to the merits; given that the present cases implicate sensitive foreign policy issues in the context of ongoing military operations, this is one of them. Pp. 11-14.

(b) Petitioners argue that they are entitled to habeas relief because they have a legally enforceable right not to be transferred to Iraqi authorities for criminal proceedings and because they are innocent civilians unlawfully detained by the Government. With respect to the transfer claim, they request an injunction prohibiting the Government from transferring them to Iraqi custody. With respect to the unlawful detention claim, they seek release but only to the extent it would not result in unlawful transfer to Iraqi custody. Because both requests would interfere with Iraq's sovereign right to "punish offenses against its laws committed within its borders," Wilson v. Girard, 354 U. S. 524 , petitioners' claims do not state grounds upon which habeas relief may be granted. Their habeas petitions should have been promptly dismissed and no injunction should have been entered. Pp. 14-28.

(1) Habeas is governed by equitable principles. Thus, prudential concerns may "require a federal court to forgo the exercise of its habeas ... power." Francis v. Henderson, 425 U. S. 536 . Here, the unusual nature of the relief sought by petitioners suggests that habeas is not appropriate. Habeas is at its core a remedy for unlawful executive detention. Hamdi v. Rumsfeld, 542 U. S. 507 . The typical remedy is, of course, release. See, e.g., Preiser v. Rodriguez, 411 U. S. 475 . But the habeas petitioners in these cases do not want simple release; that would expose them to apprehension by Iraqi authorities for criminal prosecution--precisely what they went to federal court to avoid.

The habeas petitioners do not dispute that they voluntarily traveled to Iraq, that they remain detained within the sovereign territory of Iraq today, or that they are alleged to have committed serious crimes in Iraq. Indeed, Omar and Munaf both concede that, if they were not in MNF-I custody, Iraq would be free to arrest and prosecute them under Iraqi law. Further, Munaf is the subject of ongoing Iraqi criminal proceedings and Omar would be but for the present injunction. Given these facts, Iraq has a sovereign right to prosecute them for crimes committed on its soil, even if its criminal process does not come with all the rights guaranteed by the Constitution, see Neely v. Henkel, 180 U. S. 109 . As Chief Justice Marshall explained nearly two centuries ago, "[t]he jurisdiction of the nation within its own territory is necessarily exclusive and absolute." Schooner Exchange v. McFaddon, 7 Cranch 116, 136.

This Court has twice applied that principle in rejecting claims that the Constitution precludes the Executive from transferring a prisoner to a foreign country for prosecution in an allegedly unconstitutional trial. Wilson, supra, at 529-530; Neely, supra, at 112-113, 122. Omar and Munaf concede that Iraq has a sovereign right to prosecute them for alleged violations of its law. Yet they went to federal court seeking an order that would allow them to defeat precisely that sovereign authority. But habeas corpus does not bar the United States from transferring a prisoner to the sovereign authority he concedes has a right to prosecute him. Petitioners' "release" claim adds nothing to their "transfer" claim and fails for the same reasons, given that the release they seek is release that would avoid transfer.

There is of course even more at issue here: Neely involved a charge of embezzlement and Wilson the peacetime actions of a serviceman. The present cases concern individuals captured and detained within an ally's territory during ongoing hostilities involving our troops. It would be very odd to hold that the Executive can transfer individuals such as those in the Neely and Wilson cases, but cannot transfer to an ally detainees captured by our Armed Forces for engaging in serious hostile acts against that ally in what the Government refers to as "an active theater of combat." Pp. 15-23.

(2) Petitioners' allegations that their transfer to Iraqi custody is likely to result in torture are a matter of serious concern but those allegations generally must be addressed by the political branches, not the judiciary. The recognition that it is for the democratically elected branches to assess practices in foreign countries and to determine national policy in light of those assessments is nothing new. As Chief Justice Marshall explained in the Schooner Exchange, "exemptions from territorial jurisdiction . . . must be derived from the consent of the sovereign of the territory" and are "rather questions of policy than of law, ... they are for diplomatic, rather than legal discussion." 7 Cranch, at 143, 146. In the present cases, the Government explains that it is the policy of the United States not to transfer an individual in circumstances where torture is likely to result and that the State Department has determined that the Justice Ministry--the department which has authority over Munaf and Omar--as well as its prison and detention facilities, have generally met internationally accepted standards for basic prisoner needs. The judiciary is not suited to second-guess such determinations. Pp. 23-26.

(3) Petitioners' argument that, under Valentine v. United States ex rel. Neidecker, 299 U. S. 5 , the Executive lacks discretion to transfer a citizen to Iraqi custody unless "legal authority" to do so "is given by act of Congress or by the terms of a treaty," id., at 9, is rejected. Valentine was an extradition case; the present cases involve the transfer to a sovereign's authority of an individual captured and already detained in that sovereign's territory. Wilson, supra, also forecloses petitioners' contention. A Status of Forces Agreement there seemed to give the habeas petitioner a right to trial by an American military tribunal, rather than a Japanese court, 354 U. S., at 529, but this Court found no "constitutional or statutory" impediment to the Government's waiver of its jurisdiction in light of Japan's sovereign interest in prosecuting crimes committed within its borders, id., at 530. Pp. 26-28.

No. 06-1666, 482 F. 3d 582; No. 07-394, 479 F. 3d 1, vacated andremanded.

Roberts, C. J., delivered the opinion for a unanimous Court. Souter, J., filed a concurring opinion, in which Ginsburg and Breyer, JJ., joined.

Notes:
*

* Together with No. 07-394, Geren, Secretary of the Army, et al. v. Omar et al., also on certiorari to the same court.

Petitioner pleaded guilty to making a threatening interstate communication to his ex-wife, in violation of federal law. Although the presentence report recommended a Federal Sentencing Guidelines range of 41-to-51 months in prison, the court imposed the statutory maximum sentence--60 months in prison and 3 years of supervised release--rejecting petitioner's objection that he was entitled to notice that the court was contemplating an upward departure. The Eleventh Circuit affirmed, reasoning that Federal Rule of Criminal Procedure 32(h), which states that "[b]efore the court may depart from the applicable sentencing range on a ground not identified ... either in the presentence report or in a party's pre-hearing submission, the court must give the parties reasonable notice that it is contemplating such a departure," did not apply because the sentence was a variance, not a Guidelines departure.

Held: Rule 32(h) does not apply to a variance from a recommended Guidelines range. At the time that Burns v. United States, 501 U. S. 129 , was decided, prompting Rule 32(h)'s promulgation, the Guidelines were mandatory; the Sentencing Reform Act of 1984 prohibited district courts from disregarding most of the Guidelines' "mechanical dictates," id., at 133. Confronted with the constitutional problems that might otherwise arise, the Burns Court held that the Rule 32 provision allowing parties to comment on the appropriate sentence--now Rule 32(i)(1)(C)--would be "render[ed] meaningless" unless the defendant were given notice of a contemplated departure. Id. at 135-136. Any constitutionally protected expectation that a defendant will receive a sentence within the presumptively applicable Guidelines range did not, however, survive United States v. Booker, 543 U. S. 220 , which invalidated the Guidelines' mandatory features. Faced with advisory Guidelines, neither the Government nor the defendant may place the same degree of reliance on the type of "expectancy" that gave rise to a special need for notice in Burns. Indeed, a sentence outside the Guidelines carries no presumption of unreasonableness. Gall v. United States, 552 U. S. ___, ___. Thus, the due process concerns motivating the Court to require notice in a mandatory Guidelines world no longer provide a basis for extending the Burns rule either through an interpretation of Rule 32(h) itself or through Rule 32(i)(C)(1). Nor does the rule apply to 18 U. S. C. sec.3553 variances by its terms. Although the Guidelines, as the "starting point and the initial benchmark," continue to play a role in the sentencing determination, see Gall, 552 U. S., at ___, there is no longer a limit comparable to the one in Burns on variances from Guidelines ranges that a district court may find justified. This Court is confident that district judges and counsel have the ability--especially in light of Rule 32's other procedural protections--to make sure that all relevant matters relating to a sentencing decision have been considered before a final determination is made. Pp. 5-8.

458 F. 3d 1208, affirmed.

Stevens, J., delivered the opinion of the Court, in which Roberts, C. J., and Scalia, Thomas, and Alito, JJ., joined. Thomas, J., filed a concurring opinion. Breyer, J., filed a dissenting opinion, in which Kennedy, Souter, and Ginsburg, JJ., joined.