WASHINGTON - The Supreme Court's landmark Guantanamo Bay decision yesterday could free foreign prisoners while it inflames Capitol Hill.

Some consequences are immediate, for a case that is big legally, politically and militarily. Within hours of the ruling, attorneys were preparing to demand hearings for detainees long held without charges.

These habeas corpus hearings before federal judges will force the Bush administration to reveal its evidence and expose publicly how the detainees have been treated. Some attorneys think the administration will simply start releasing detainees to avoid the potentially embarrassing hearings altogether.

"Frankly, I don't think the government is going to want to continue to hold these detainees," predicted Matthew MacLean, cocounsel for detainee Fawzi al Odah.

Eugene Fidell, president of the National Institute of Military Justice, agreed that the ruling would provide "additional incentive for the administration to repatriate as many people as possible."

MacLean, a former Army prosecutor, said the habeas corpus petitions of 100 to 200 detainees had been on hold waiting for the high court to rule. Now that it has, Odah and others can pursue their cases before various judges in the U.S. Court of Appeals for the District of Columbia Circuit.

Yesterday's decision allows lawyers to file petitions one by one challenging the detentions of named prisoners. It also allows judges who had put earlier petitions on hold to reactivate the files.

The ruling also will propel action on Capitol Hill, where lawmakers including Sen. Dianne Feinstein (D., Calif.) yesterday accelerated their demands to shut down Guantanamo. Feinstein's bill ordering the closure has five cosponsors.

"The question of closing Guantanamo is a matter of when, and not if," Feinstein said on the Senate floor.

On the flip side, Sen. Lindsey Graham (R., S.C.) said he would "explore the possibility of a constitutional amendment to blunt the effect of this decision." This is an extreme long shot, though lawmakers could vent about the alleged dangers that Odah and his fellow detainees pose.

But Sen. Arlen Specter of Pennsylvania, ranking Republican on the Judiciary Committee, told the Washington Post that the limited information made public so far about the detainees' cases had been unconvincing.

"I think that while there are still tremendous concerns about a terrorist threat, the administration has not made its case that the people in Guantanamo really are threats," he said.

In the habeas corpus hearings, the burden will be on the government to show that it has sufficient evidence that the men are enemy combatants and can be charged with crimes. While it is unlikely any of the detainees will appear at the hearings, they will be able to offer exculpatory evidence. Judges can settle on remedies that include ordering release.

"My guess is we're going to see a high number of people who the government will have to release," said Michael Ratner, president of the Center for Constitutional Rights.

The center brought the first lawsuits in 2002 challenging the Bush administration's treatment of alleged enemy combatants. Since those early lawsuits, about 600 pro bono attorneys have rallied to the cause of the Guantanamo detainees.

Ratner noted that the decision did not directly apply to captives facing charges by military commissions set up by the Bush administration and approved by Congress in 2006. In the long run, though, some attorneys suggested that those facing commissions still might try filing habeas corpus petitions to challenge the commissions.

Twenty men currently face trials before military commissions. They include alleged 9/11 mastermind Khalid Shaikh Mohammed - a Pakistani once held by the CIA who is now charged with a crime punishable by death - and Osama bin Laden's driver, Salim Hamdan - a Yemeni charged with supporting al-Qaeda, a crime with a maximum penalty of life in prison.

Justice Department spokesman Peter Carr said yesterday: "While we disagree with the ruling, it is important to note that the Boumediene case did not involve military commissions. Military commission trials will continue to go forward."

The court noted that the hearings could implicate "sources and methods" of intelligence-gathering, but it expressed confidence that federal judges could protect sensitive information.

One of the next big questions - or embarrassments - could involve what happens to detainees who win their freedom at habeas corpus hearings but have no place else to go.

"The brutally frank answer is that we're stuck," Defense Secretary Robert M. Gates told senators recently. "And we're stuck in several ways: Either their home government won't accept them, or we are concerned that the home government will let them loose once we return them home."