Today’s ruling by the Supreme Court in Boumediene v. Bush delivered a dramatic blow to the President’s lawless detention policies and overturned an effort by the previous Congress to eliminate the centuries-old right of habeas corpus. The ruling means that prisoners at the US military base at Guantanámo Bay, who have been held for more than six years without charge, will finally have the opportunity to challenge the accusations against them in a court of law. More broadly, the ruling rejects the premise on which Guantánamo is based: that the President can create a lawless enclave simply by incarcerating people outside the mainland United States.

Boumediene marks the culmination of the quest for due process that began in 2002, when the first habeas corpus petitions were filed by Guantánamo detainees in federal court. In 2004, the Supreme Court ruled in Rasul v. Bush that the detainees had a right to habeas corpus under a statute that dated to the nation’s founding. The Administration, however, then sought to block any of the cases from going forward, arguing that the detainees had no rights to enforce beyond filing a piece of paper called “habeas corpus” and that any rights they did have were satisfied by the summary military proceedings it had hastily put in place after the Supreme Court’s decision.

Congress, in turn, twice tried to eliminate habeas rights for detainees. The Supreme Court rejected the first attempt in 2006, ruling in Hamdan v. Rumsfeld that the legislation did not apply to pending cases. So Congress tried again with the Military Commissions Act of 2006 (MCA), which made explicit that the elimination of habeas rights applied to all Guantánamo cases, past, present and future. The issue before the Supreme Court in Boumediene was whether the MCA violated the constitutional guarantee of habeas corpus, known as the “Suspension Clause.”

The first question the Court addressed in Boumediene was whether the Guantánamo detainees had a right to habeas corpus. The Administration had argued that because the prisoners were foreign nationals held outside the sovereign territory of the United States, they had no rights under the Constitution. As a result, the President and Congress were free to deny them any access to the courts at all.

The Supreme Court rejected this argument in no uncertain terms. As Justice Anthony M. Kennedy explained in his 5-4 opinion for the Court, formal constructs like “sovereignty” do not and cannot dictate the presence or absence of constitutional rights because they are “subject to manipulation by those whose power it is designed to restrain.”

Boumediene thus sounded a death-knell to the idea of Guantánamo itself: that the President can imprison people indefinitely without court review simply by bringing them to a US enclave on an island in the Caribbean. Instead, Kennedy’s opinion adopts a more flexible and pragmatic approach under which the Constitution’s applicability to those beyond America’s shores depends on a practical assessment of the circumstances. And under that approach, the application of fundamental constitutional rights at Guantánamo, where individuals have been detained for more than six years in territory under total US control, is a no-brainer.

The ruling that the Guantánamo detainees are protected by the Constitution, however, did not end the case. The government had also argued that the process Congress created in 2005 in place of habeas corpus satisfied all the rights Guantánamo detainees had. This process had two parts: first, the summary military hearing, known as a Combatant Status Review Tribunal (CSRT); and second, limited review of the CSRT’s decision by the court of appeals in Washington, DC, pursuant to the Detainee Treatment Act of 2005.

The Supreme Court made clear that Congress can create a constitutionally adequate substitute for habeas corpus without running afoul of the Suspension Clause if that substitute provides what habeas corpus provides. But the Court also ruled that Congress had unmistakably failed to provide an adequate substitute for habeas corpus for Guantánamo detainees.

The reason, the Court explained, was that the habeas itself requires an opportunity for a prisoner to see the allegations against him, to respond to those allegations with the assistance of counsel, and to a determination by an independent judge. The CSRT, by contrast, relied primarily on secret accusations denied prisoners the assistance of counsel and an opportunity to submit evidence showing their innocence, and lacked neutrality. Any court review limited to such a sham hearing, the Supreme Court said, was tantamount to no review at all.

In another decision issued today, the Court reaffirmed the right of American citizens to habeas corpus no matter where they are held. The Court ruled in Munaf v. Geren that two American citizens detained in Iraq have a right to habeas corpus. In so doing, the Court rejected the government’s argument that the President could avoid the reach of habeas corpus by claiming that the United States was holding the prisoners under “international authority”–in that case, a UN Security Council Resolution. While the Court agreed with the government that the prisoners could not obtain review of their transfer to Iraqi custody, it made clear that American citizens have the right to habeas corpus as long as they are held by their government, no matter where they are detained or what label is attached to their detention.

Today’s ruling in Boumediene does not require the release of any prisoner at Guantánamo. Instead, it merely mandates that the 275 prisoners who are still there must receive what they should have received long ago: an opportunity to challenge their imprisonment in court. In a country committed to justice and the rule of law nothing less is acceptable. While it has taken almost seven years to vindicate this most modest principle, late is better than never.