[1][2][3][4][5] The case underscored the essential role of habeas corpus as a safeguard against government overreach, ensuring that individuals cannot be detained indefinitely without the opportunity to challenge the legality of their detention.

The ruling challenged the government’s assertion of unchecked executive power, emphasizing that such authority cannot override the fundamental protections guaranteed by the Constitution.

Many captives from the war were held at Camp X-Ray, which was opened at the United States' Guantanamo Bay Naval Base in Cuba in January 2002.

Seven months later, the Supreme Court ruled in Hamdan v. Rumsfeld (2006) that only Congress and not the Executive Branch has the Constitutional authority to set up military commissions to try captives taken in the "war on terror".

[13] The Supreme Court received over two dozen briefs of amicus curiae on the case, including some written strictly on the history and application of Habeas Corpus in England, Scotland, Hanover, Ireland, Canada, British-controlled territories, India, and the United States.

[16][17][18][19] The court found that the petitioners had met their burden of establishing that the Detainee Treatment Act of 2005 failed to provide an adequate substitute for habeas corpus.

Kennedy's majority opinion begins with an over-twenty page review of the history of habeas corpus in England from its roots in the due process clause of Magna Carta of 1215 to the 19th century.

The majority opinion rejected the government's argument comparing the habeas corpus restriction under the MCA to those affected by the Antiterrorism and Effective Death Penalty Act of 1996, which were ruled constitutional after a suspension clause challenge.

"[23] The commission of terrorist acts by some former prisoners at Guantanamo Bay after their release "illustrates the incredible difficulty of assessing who is and who is not an enemy combatant in a foreign theater of operations where the environment does not lend itself to rigorous evidence collection.

"[24] A consequence of the Court's majority decision will be that "how to handle enemy prisoners in this war will ultimately lie with the branch [the judiciary] that knows least about the national security concerns that the subject entails.

"[26] Justice Scalia added that the Court's majority "admits that it cannot determine whether the writ historically extended to aliens held abroad, and it concedes (necessarily) that Guantanamo Bay lies outside the sovereign territory of the United States.

This line of reasoning was arguably more in line with the plain reading of Johnson v. Eisentrager (1950) (which denied German prisoners of war habeas rights primarily due to both practical logistical concerns and the determination that they had been afforded an adequate substitute: traditional military war crimes trials, which complied with the Geneva Conventions) than that of Justice Scalia, and also avoided the more controversial and complicated issue of whether the detainees were entitled to file habeas petitions in the first place.

[34] In Boumediene v. Bush (2008), the Supreme Court had ruled for the first time that Guantánamo detainees were entitled to submit habeas corpus petitions directly to federal judges in Washington to determine whether the U.S. government had enough evidence to justify their continued open-ended detention without charge.

The decision said in part: "We do consider it uncontroversial … that the privilege of habeas corpus entitles the prisoner to a meaningful opportunity to demonstrate he is being [unlawfully] held.

"[35] The decision added: "The habeas court must have sufficient authority to conduct a meaningful review of both the cause for detention and the Executive's power to detain.

Specifically, the US appeals court required federal judges hearing Guantánamo cases to accord a special presumption of accuracy to US intelligence reports being used to justify continued detention.

[35] "The entire point of the habeas hearing is to force the government to justify its detention of people who have been neither charged nor convicted, not to allow it to skate by with presumption," Livingston said.

He said the appeals court's requirement of a pro-government presumption in favor of US intelligence reports "comes perilously close to suggesting that whatever the government says must be treated as true.

"[35] According to a study by legal scholars at the Center for Policy and Research at Seton Hall University School of Law, between 2008 and July 2010, Guantánamo detainees won 56 percent of their habeas challenges in federal court.

That means that prior to July 2010, a federal judge agreed with 19 of 34 detainees who claimed there was insufficient evidence to justify his open-ended detention at Guantánamo and ordered the release of each.