WASHINGTON — The Supreme Court ruled today that foreign terrorism suspects held at Guantanamo Bay have rights under the Constitution to challenge their detention in American civilian courts.

In its third rebuke of the Bush administration’s treatment of prisoners, the court ruled 5-4 that the government is violating the rights of prisoners being held indefinitely and without charges at the American naval base at Cuba. The court’s liberal justices were in the majority.

Justice Kennedy, writing for the court, said, “The laws and Constitution are designed to survive, and remain in force, in extraordinary times.”

Justice Kennedy said federal judges could ultimately order some detainees to be released, but that such orders would depend on security concerns and other circumstances.

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The White House had no immediate comment on the ruling. The White House press secretary, Dana Perino, traveling with President Bush in Rome, said the administration was reviewing the opinion.

It was not immediately clear whether this ruling, unlike the first two, would lead to prompt hearings for the detainees, some of whom have been held more than 6 years. Roughly 270 men remain at the island prison, classified as enemy combatants and held on suspicion of terrorism or links to Al Qaeda and the Taliban.

The ruling could resurrect many detainee lawsuits that federal judges in Washington put on hold pending the outcome of the high court case. The decision sent judges, law clerks, and court administrators scrambling to read Justice Kennedy’s 70-page opinion and figure out how to proceed. The Chief Judge of the United States District Court for the District of Columbia, Royce C. Lamberth, said he would call a special meeting of federal judges to address how to handle the cases.

The decision also cast doubt on the future of the military war crimes trials that 19 detainees are facing so far. The Pentagon has said it plans to try as many as 80 men held at Guantanamo.

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

The administration opened the detention facility at Guantanamo Bay shortly after the September 11, 2001 terrorist attacks to hold enemy combatants, people suspected of ties to Al Qaeda or the Taliban.

The Guantanamo prison has been harshly criticized at home and abroad for the detentions themselves and the aggressive interrogations that were conducted there.

The court said not only that the detainees have rights under the Constitution, but that the system the administration has put in place to classify them as enemy combatants and review those decisions is inadequate.

The administration had argued first that the detainees have no rights. But it also contended that the classification and review process was a sufficient substitute for the civilian court hearings that the detainees seek.

In dissent, Chief Justice Roberts criticized his colleagues for striking down what he called “the most generous set of procedural protections ever afforded aliens detained by this country as enemy combatants.”

Justices Alito, Scalia, and Thomas also dissented.

Justice Scalia said the nation is “at war with radical Islamists” and that the court’s decision “will make the war harder on us. It will almost certainly cause more Americans to be killed.”

Justices Breyer, Bader Ginsburg, Souter, and Stevens joined Justice Kennedy to form the majority.

Justice Souter wrote a separate opinion in which he emphasized the length of the detentions.

“A second fact insufficiently appreciated by the dissents is the length of the disputed imprisonments, some of the prisoners represented here today having been locked up for six years,” Justice Souter said. “Hence the hollow ring when the dissenters suggest that the court is somehow precipitating the judiciary into reviewing claims that the military … could handle within some reasonable period of time.”

The court has ruled twice previously that people held at Guantanamo without charges can go into civilian courts to ask that the government justify their continued detention. Each time, the administration and Congress, then controlled by Republicans, changed the law to try to close the courthouse doors to the detainees.

The court specifically struck down a provision of the Military Commissions Act of 2006 that denies Guantanamo detainees the right to file petition of habeas corpus.

Habeas corpus is a centuries-old legal principle, enshrined in the Constitution, that allows courts to determine whether a prisoner is being held illegally.

The head of the New York-based Center for Constitutional Rights, which represents dozens of prisoners at Guantanamo, welcomed the ruling.

“The Supreme Court has finally brought an end to one of our nation’s most egregious injustices,” the CCR Executive Director, Vincent Warren, said. “By granting the writ of habeas corpus, the Supreme Court recognizes a rule of law established hundreds of years ago and essential to American jurisprudence since our nation’s founding.”

Five alleged plotters of the September11 attacks appeared in a Guantanamo courtroom last week for a hearing before their war crimes trial, which prosecutors hope will start September 15.

A Pentagon spokesman, Navy Commander Jeffrey Gordon, said he had no immediate information whether a hearing at Guantanamo for a Canadian charged with killing an American Special Forces soldier at Afghanistan, , Omar Khadr, would go forward next week as planned.

Mr. Bush has said he wants to close the facility once countries can be found to take the prisoners who are there.

The presidential candidates, Senators McCain and Obama, also support shutting down the prison.