Justices agreed Friday to hear the appeal of terror suspect al-Marri, held without charge for more than five years.
The US Supreme Court has agreed to take up the case of Ali Saleh al-Marri, a graduate student and suspected Al Qaeda sleeper agent who has been held without charge in a US military prison for more than five years.
The high court made the announcement on Friday after its private conference.
The case poses the most significant unresolved legal question yet in the Bush administration's controversial approach to the war on terror, and it sets the stage for another potential landmark national security decision next June.
At issue is whether the president has the power to order someone who is legally present in the United States to be held in indefinite military detention as an "enemy combatant."
The Fourth US Circuit Court of Appeals ruled 5 to 4 in July that Congress had given the president the power to declare and hold enemy combatants, including individuals who are legally present in the US.
Lawyers for Mr. Marri are appealing that decision, saying civilians in the US may only be detained through the criminal-justice system. They are asking the nation's highest court to state clearly what the law is and what it requires.
"The lower court has replaced settled and historic protections with confusion," writes Marri's lawyer, Jonathan Hafetz of the American Civil Liberties Union, in his brief to the court. "The Fourth Circuit has cast a pall over the physical liberty of all persons in the United States."