WASHINGTON—Terrorist enemies or hapless innocents? Whatever the truth, the hundreds of foreigners held without charges at Guantanamo Bay have rights under the U.S. Constitution, the Supreme Court says.

And, considering that many have been imprisoned at the Cuban camp for six years, they should be able to exercise those rights quickly and ask civilian judges to force the government to justify their detention, the court ruled Thursday.

The court, though deeply divided, issued a strong rebuke to President Bush’s anti-terror policies. It was the third time the justices have repudiated the president on the detainees, though they still have not made it through the courthouse door.

“It’s a total loss for the government,” said former federal prosecutor Andrew McBride, who disagreed with the court’s ruling.

Bush said he, too, disagreed and suggested he might seek yet another law to keep terror suspects locked up at the prison camp, even as his presidency winds down and Democrats control Congress.

Justice Anthony Kennedy, writing for the 5-4 high court majority, acknowledged the terrorism threat the U.S. faces—the administration’s justification for the detentions—but he declared, “The laws and Constitution are designed to survive, and remain in force, in extraordinary times.”

In a blistering dissent, Justice Antonin Scalia said the decision “will make the war harder on us. It will almost certainly cause more Americans to be killed.”

Bush has argued the detentions are needed to protect the nation in a time of unprecedented threats from al-Qaida and other foreign terrorist groups. The president, in Rome, said Thursday, “It was a deeply divided court, and I strongly agree with those who dissented.” He said he would consider whether to seek new laws in light of the ruling “so we can safely say to the American people, ’We’re doing everything we can to protect you.”’

Kennedy said federal judges could ultimately order some detainees to be released, but he also said such orders would depend on security concerns and other circumstances. The ruling itself won’t result in any immediate releases.

The decision also cast doubt on the future of the military war crimes trials that 19 detainees, including Khalid Sheikh Mohammed and four other alleged Sept. 11 plotters, are facing so far. The Pentagon has said it plans to try as many as 80 men held at Guantanamo.

Lawyers for detainees differed over whether the ruling, unlike the first two, would lead to prompt hearings for those who have not been charged. Roughly 270 men remain at the prison at the U.S. naval base in Cuba. Most are classed as enemy combatants and held on suspicion of terrorism or links to al-Qaida and the Taliban. Several dozen have been cleared for release, but the government has not found a country willing to take them or the detainees have objected to being sent somewhere they fear they could be tortured.

Some detainee lawyers said hearings could take place within a few months. But James Cohen, a Fordham University law professor who has two clients at Guantanamo, predicted Bush would continue seeking ways to resist the ruling. “Nothing is going to happen between June 12 and Jan. 20,” when the next president takes office, Cohen said.

Roughly 200 detainees have lawsuits on hold in federal court in Washington. Chief Judge Royce C. Lamberth said he would call a special meeting of federal judges to address how to handle the cases.

Detainees already facing trial are in a different category.

Justice Department spokesman Peter Carr said Thursday’s decision should not affect war crimes trials. “Military commission trials will therefore continue to go forward,” he said.

The lawyer for Salim Ahmed Hamdan, Osama bin Laden’s one-time driver, said he will seek dismissal of the charges against Hamdan based on the new ruling. A military judge had already delayed the trial’s start to await the high court ruling.

It was unclear whether a hearing at Guantanamo for Canadian Omar Khadr, charged with killing a U.S. Special Forces soldier in Afghanistan, would go forward next week as planned.

Charles Swift, the former Navy lawyer who used to represent Hamdan, said he believes the court removed any legal basis for keeping the Guantanamo facility open and that the military tribunals are “doomed.”

Guantanamo generally and the tribunals were conceived on the idea that “constitutional protections wouldn’t apply,” Swift said. “The court said the Constitution applies. They’re in big trouble.”