Following the 9/11 terrorist attacks, Congress authorized the President's use of "all necessary and appropriate force" against those "nations, organizations, or persons" who "planned, authorized, committed, or aided the terrorist attacks." As a result of subsequent military action, particularly in Afghanistan, the United States captured numerous persons whom it suspected of ties to Al Qaeda or the Taliban—groups alleged to have perpetrated the 9/11 attacks or to have aided the perpetrators. The United States transferred many such persons to the U.S. Naval Station at Guantanamo Bay, Cuba. The Guantanamo detentions prompted difficult legal questions regarding wartime detention and the separation of powers, some of which had previously been explored only in the context of traditional wars. What legal frameworks limit the Executive's authority to detain and try persons captured in a military conflict as it sees fit? Do statutory and constitutional rights to challenge one's detention extend to non-citizens detained outside of the United States? In what circumstances may Congress limit the federal courts' jurisdiction over petitions for habeas corpus? Justice Stevens has been a key player in the Supreme Court's resolution of such questions. He authored majority opinions in two significant cases, Rasul v. Bush and Hamdan v. Rumsfeld . In those cases, the Court decided questions regarding Guantanamo detainees' access to habeas review on statutory grounds, without addressing whether the U.S. Constitution might guarantee such a right. Nevertheless, they arguably provided the legal underpinning for the 2008 decision Boumediene v. Bush , in which the Court reached the constitutional question. Likewise, although the Hamdan decision struck down early military commission procedures on statutory grounds, it arguably framed the Court's approach to reviewing the balance of the three branches' powers during wartime and set the stage for future reviews of military commission procedures. Justice Stevens might also be characterized as the leading voice among the justices encouraging the Court to rule on difficult separation-of-powers questions implicated by wartime detentions. In 2004, for example, he wrote a dissenting opinion, joined by three other justices, in Rumsfeld v. Padilla . The case involved a man, determined by the President to be an enemy combatant, arrested in Chicago and detained in a military brig. The Court resolved his subsequent habeas challenge on statutory grounds, and did not resolve questions regarding the President's authority to conduct military detentions. In dissent, Justice Stevens argued that the Court had a duty to address the "questions of profound importance to the Nation" raised in the case. He used relatively strong language to describe the importance of the questions at stake, concluding with the argument that "if this Nation is to remain true to the ideals symbolized by its flag, it must not wield the tools of tyrants even to resist an assault by the forces of tyranny." Over time, the writ of habeas corpus has evolved as the primary means to challenge executive detentions. The U.S. Constitution does not mention the writ, except to limit the circumstances in which it may be suspended. A federal statute, 28 U.S.C. § 2241, provides the federal courts with jurisdiction to grant writs of habeas corpus to specified petitioners, including those whose custody is shown to violate the U.S. Constitution, federal statute, or international law. However, the writ has a history "antecedent to statute … throwing its root deep into the genius of our common law." Thus, the historical use and interpretation of the writ are crucial factors for interpreting its scope. It is common for Supreme Court justices to emphasize history in their interpretation of the habeas writ; however, their views of history differ. A case decided shortly before the 9/11 attacks, INS v. St. Cyr , offers a pre-9/11 glimpse of Justice Stevens's historical interpretation of the writ. In that case, a lawful permanent resident of the United States was subject to deportation by the executive branch because of an earlier conviction, but a legal issue arose on whether he was eligible for discretionary relief from removal. He filed a habeas petition in federal court to challenge his continued detention pending deportation. Although the case was resolved on statutory grounds, Justice Stevens emphasized the traditional role the habeas writ plays in limiting executive-branch detention authority. Writing for the majority in the 5-4 case, he asserted that "[a]t its historical core, the writ of habeas corpus has served as a means of reviewing the legality of Executive detention…." Contrasting petitions brought to challenge detentions initiated by the executive with petitions asserted in other contexts, including petitions filed by prisoners convicted by criminal courts, he asserted that "it is in [the executive detention] context that [the writ's] protections have been the strongest." This view of the habeas writ's historical role appeared to inform Justice Stevens's approach in post-9/11 cases. For example, in Hamdan , he emphasized the "compelling historical precedent" supporting civilian courts' intervention in military commission proceedings. Some commentators have characterized the post-9/11 wartime detention cases as evidencing a jurisprudential clash between Justice Stevens and Justice Scalia. Nevertheless, though subsequently drawing differing conclusions from its application, the two justices have proceeded from a common analytical premise, as evidenced in Hamdi v. Rumsfeld , one of the early landmark cases decided after the 9/11 attacks. In that case, a plurality of the Supreme Court justices upheld, with limitations, the domestic detention of a U.S. citizen who was captured in Afghanistan and alleged to have been fighting for the Taliban. In a dissenting opinion, Justices Stevens and Scalia agreed on a position that none of the other justices shared. Specifically, they viewed the domestic, preventative (i.e., non-criminal) detention of a U.S. citizen as exceeding the Executive's power. The dissenting opinion articulated the most restrictive view of executive power among the various opinions. It asserted that, historically, "the Executive's assertion of military exigency has not been thought sufficient to permit detention without charge." However, as the factual scenarios moved beyond U.S. boundaries and involved non-citizens—including in Rasul (decided the very same day as Hamdi )—the two justices' interpretations diverged. Although both justices emphasized historical context and prior precedents, they reached opposite conclusions. Specifically, whereas Justice Stevens continued to interpret executive authority relatively narrowly as applied to non-citizens in Guantanamo, Justice Scalia perceived a historical distinction between the treatment of detainees on U.S. soil, on one hand, and the treatment of aliens outside U.S. territory, on the other hand. That difference is evident throughout the post-9/11 wartime detention cases. In several dissenting opinions, Justice Scalia argued in favor of bright-line rules, in which jurisdiction would end at the boundaries of U.S. sovereign territory. In contrast, Justice Stevens adopted a more case-specific approach, in which history and precedents were viewed as supporting the application of rights and jurisdiction to Guantanamo detainees. One result of this split was that if Justice Scalia's approach had prevailed in the post-9/11 cases, the Court would have resolved many of the wartime detention cases by declining to exercise jurisdiction. Instead, Justice Stevens's approach led to the Court's resolution of various questions on the merits. After 9/11, numerous Guantanamo detainees submitted habeas petitions in federal courts to challenge their detentions. The petition in Rasul was filed on behalf of two Australian and 12 Kuwaiti citizens whom the United States had captured in Afghanistan. The question before the Court was whether the federal habeas statute granted jurisdiction to consider petitions brought by non-citizens located in Guantanamo. The government argued that the statute did not apply extraterritorially. The statutory text made no reference to petitioners' geographic location or citizenship. Supreme Court precedents did not necessarily decide the issue. In several cases predating the habeas statute, the Court upheld federal courts' jurisdiction over writs of habeas corpus challenging wartime detentions. However, those cases typically involved persons detained in the United States. In contrast, in Johnson v. Eisentrager , a post-World War II case decided a few years after Congress enacted the current habeas statute, petitioners were serving sentences in Germany after a trial by a U.S. military commission in China. Noting six factors, the Court held that the courts lacked jurisdiction over the Eisentrager petitions. Writing for the five-justice majority in Rasul , Justice Stevens relied on case-specific facts to distinguish Eisentrager and hold that the "[a]pplication of the habeas statute to persons detained at [Guantanamo] is consistent with the historical reach of the writ of habeas corpus." To reach that conclusion, he characterized the Eisentrager holding as limited to its facts. He then distinguished the Guantanamo detainees from the petitioners in Eisentrager , concluding that the two groups "differ … in important respects." In particular, he emphasized that unlike the Eisentrager petitioners, the Guantanamo detainees were not alien enemy combatants in a traditional conflict between state armies. He also noted that unlike its detention facility in post-war Germany, the United States exercises "complete jurisdiction and control" over the Guantanamo Naval Station, pursuant to an agreement with Cuba. Justice Stevens relied on a second line of argument to support the Court's holding. He recalled Ahrens v. Clark , a case decided a few years prior to Eisentrager , in which the Court interpreted the federal habeas statute as not providing jurisdiction for petitions brought by persons located outside of a court's territorial jurisdiction. (Justice Stevens was well situated to recollect that case: when the Court considered Ahrens , he was serving as a law clerk for Justice Rutledge, who wrote a dissenting opinion.)