The Supreme Court today agreed to hear a major case challenging the legality of the military commissions established by the Bush administration to try alleged terrorism suspects.

In agreeing to review the challenge brought on behalf of Salim Ahmed Hamdan, 34, a Yemeni mechanic who admits that he served as Osama bin Laden's driver, the justices rejected a plea from the government to hold off any consideration of the case until after proceedings against Hamdan are concluded.

Hamdan has been detained at the U.S. naval base at Guantanamo Bay, Cuba, for the past 21 months and is accused of being a member of al Qaeda.

The fact that the court agreed to review the case does not guarantee a decision on the fundamental questions. The Supreme Court could avoid those questions by agreeing with the government that any substantive review should await the conclusion of the military commission proceedings against Hamdan.

In the alternative, the court could consider whether President Bush has exceeded his inherent powers as commander in chief and the powers granted to him by Congress after Sept. 11, 2001. The court could also decide whether Geneva Conventions governing the treatment of prisoners of war affords any legal protections to Guantanamo prisoners such as Hamdan.

Numerous organizations had filed friend-of-the-court briefs urging the Supreme Court to intervene in the Hamdan case. Among them was a group of retired generals and admirals, who argued that the administration's position "immediately and directly" endangers American soldiers and "undermines the laws of war."

It is the third Supreme Court case stemming from the government's claim of expansive power to deal with alleged terrorists.

In 2004, the court struck down key elements of the Bush administration's legal policy for its battle against terrorism, ruling in two cases that the executive branch does not have the authority to deprive U.S. citizens of their liberty without giving them a day in some type of court.

The court also ruled that each of the 595 alleged members of al Qaeda and the Taliban being held at Guantanamo has the right to ask a U.S. judge to set him free.

The case of Hamdan, a non-U.S. citizen, raises two fundamental issues. He contends that the president exceeded his legal and constitutional powers in establishing military commissions to try those held at Guantanamo. The commissions afford defendants few of the rights afforded to individuals tried either by the U.S. courts or conventional military courts.

Hamdan and his lawyers also contend that the Geneva Conventions governing treatment of prisoners of war may be enforced in federal court. Prisoners of war are supposed to be tried in courts-martial rather than by the less formal military commissions. Hamdan, who has claimed that he took his job solely for money and not for ideology, has sought a court-martial. But the administration has vigorously sought to avoid courts-martial, which have rules that make it more difficult to keep defendants from knowing all the evidence against them.

In today's action, the court said it would review a decision by the U.S. Court of Appeals for the D.C. Circuit that upheld the government's power, saying it was authorized by Congress when it gave Bush authority after Sept. 11, 2001, to "use all necessary and appropriate force" against terrorists and potential terrorists.

The appeals court also rejected the Geneva Convention argument.

Among the members of the appeals court panel was John G. Roberts, Jr., now chief justice. Roberts did not participate in today's action. That suggests, but does not guarantee, that he will recuse himself from considering the case as well.

The Justice Department, in opposing Hamdan's petition, argued that it was "premature." "Further proceedings before the military commission may make it unnecessary for this Court to address any number of the questions currently presented in the case," government lawyers said. "If the commission finds petitioner not guilty, the Court can avoid these issues altogether."

It contended, as well, the court interference in the proceedings would encroach on the president's authority as commander in chief as well as the powers granted to him by Congress after Sept. 11.

On the Geneva Convention issue, the government based its case on a 1950 Supreme Court ruling in Johnson v. Eistentrager, involving German nationals convicted by a military commission in China of violating the laws of war. Under that decision, the government contends, rights granted under the Geneva Convention are not enforceable in U.S. Courts.