U.S. Officials Scramble to Find Options

"There's no particular direction that we're heading in right now except to review the decision and consider all options that would be available to us and Congress," one official said.

Several officials said the U.S. courts are too limiting, in part because the strict rules of evidence could cause problems in cases in which suspects were arrested by a foreign government, held for years and transferred without critical evidence -- and whose trials would require the presence of witnesses who are difficult, if not impossible, to locate.

Many experts and human rights groups favored the use of the UCMJ, which they described as transparent and fair.

"You could pass legislation that authorizes military commissions that look essentially like military courts-martial and that would be consistent with the decision, but why do that when we already have courts-martial that are consistent with the decision?" asked Tom Malinowski, Washington advocacy director for Human Rights Watch.

Rights groups hailed the decision as a major victory for the rule of law in America. The ruling appeared to grant detainees certain protections under the Geneva Conventions Common Article 3, which could require the U.S. government to treat all detainees in the war on terrorism -- whether they are held in the United States or abroad, or in secret facilities operated by the CIA -- according to international standards.

"Just because you're a president at war doesn't mean the law ceases to exist," said Jumana Musa, a lawyer at Amnesty International. "The best-case scenario now is that they charge the detainees under an established system of law. If they're not going to charge them, they need to release them."

Unlike evidence in most criminal or military court proceedings, the bulk of the government's evidence against suspected terrorists at Guantanamo Bay can be circumstantial and classified. The cases against many Guantanamo Bay detainees may rest on statements gleaned from interrogations of prisoners throughout the world, as well as from intelligence collected by the CIA and others.

Safeguarding such information is a principal concern of the U.S. government. "In most situations, that's always going to be the overriding concern," said Robert McNamara, a CIA general counsel until 2001. "You shouldn't have to decide to let someone go to protect sources and methods."

The State Department has sought to transfer all but the most dangerous detainees to their countries of origin. But this has proved problematic for several reasons, said Pierre Prosper, the State Department's former ambassador at large for war crimes, who spent most of his tenure traveling the globe to work out such transfers.

"Some countries had reservations about inheriting the security risk that the detainees posed," Prosper said. Others did not have the secure prisons and professional guards necessary to assure U.S. authorities that they would remain in custody.

In other cases, particularly in Europe, it would be illegal to hold detainees transferred from Guantanamo Bay unless they could be charged with a specific crime. In some cases, the U.S. military is unwilling to give European authorities the classified evidence they would need

John B. Bellinger III, legal adviser to Secretary of State Condoleezza Rice, said this week that relocation efforts continue, especially for about 300 detainees from Afghanistan, Saudi Arabia and Yemen, who make up about two-thirds of Guantanamo Bay's population.

"We want to get out of the Guantanamo business if we can," Bellinger said.

Staff writers Dana Priest and Michael Abramowitz, and researcher Julie Tate contributed to this report.