Ruling in the case of American-born detainee Yaser Esam Hamdi, Justice Sandra Day O'Connor said the court has "made clear that a state of war is not a blank check for the president when it comes to the rights of the nation's citizens."
Congress did give the president authority to hold Hamdi, a four-justice plurality of the court said, but that does not cancel out the basic right to a day in court. (Padilla case background)
The court ruled similarly in the case of about 600 non-U.S.-born men held indefinitely at a U.S. Navy prison at Guantanamo Bay, Cuba. The men can use American courts to contest their captivity and treatment, the high court said. (Detainees case background)
Steven R. Shapiro, legal director of the ACLU, called the rulings "a strong repudiation of the administration's argument that its actions in the war on terrorism are beyond the rule of law and unreviewable by American courts."
The court sidestepped a third major terrorism case, ruling that a lawsuit filed on behalf of detainee Jose Padilla improperly named Defense Secretary Donald H. Rumsfeld instead of the much lower-level military officer in charge of the Navy brig in South Carolina where Padilla has been held for more than two years.
The court left hard questions unanswered in all three cases.
The administration had fought any suggestion that Hamdi or another U.S.-born terrorism suspect could go to court, saying that such a legal fight posed a threat to the president's power to wage war as he sees fit.
"We have no reason to doubt that courts, faced with these sensitive matters, will pay proper heed both to the matters of national security that might arise in an individual case and to the constitutional limitations safeguarding essential liberties that remain vibrant even in times of security concerns," Justice Sandra Day O'Connor wrote in the Hamdi case.
O'Connor said that Hamdi "unquestionably has the right to access to counsel."
The court threw out a lower court ruling that supported the government's position fully, and Hamdi's case now returns to a lower court.
The Bush administration contends that as "enemy combatants," the men are not entitled to the usual rights of prisoners of war set out in the Geneva Conventions. Enemy combatants are also outside the constitutional protections for ordinary criminal suspects, the government has claimed.
The administration argued that the president alone has authority to order their detention, and that courts have no business second-guessing that decision