Washington - Foreign terrorism suspects held at the Guantánamo Bay naval base in Cuba have constitutional rights to challenge their detention there in United States courts, the Supreme Court ruled, 5 to 4, on Thursday in a historic decision on the balance between personal liberties and national security.

    "The laws and Constitution are designed to survive, and remain in force, in extraordinary times," Justice Anthony M. Kennedy wrote for the court.

    The ruling came in the latest battle between the executive branch, Congress and the courts over how to cope with dangers to the country in the post-9/11 world. Although there have been enough rulings addressing that issue to confuse all but the most diligent scholars, this latest decision, in Boumediene v. Bush, No. 06-1195, may be studied for years to come.

    The justices rejected the administration's argument that the individual protections provided by the Detainee Treatment Act of 2005 and the Military Commissions Act of 2006 were more than adequate.

    "The costs of delay can no longer be borne by those who are held in custody," Justice Kennedy wrote, assuming the pivotal rule that some court-watchers had foreseen.

    Joining Justice Kennedy's opinion were Justices John Paul Stevens, Stephen G. Breyer, Ruth Bader Ginsburg and David H. Souter.

    The dissenters were Chief Justice John G. Roberts Jr. and Justices Samuel A. Alito Jr., Antonin Scalia and Clarence Thomas, generally considered the conservative wing on the tribunal.

    The 2006 Military Commission Act stripped the federal courts of jurisdiction to hear habeas corpus petitions filed by detainees challenging the bases for their confinement. That law was upheld by the United States Court of Appeals for the District of Columbia Circuit in February 2007.

    At issue were the "combatant status review tribunals," made up of military officers, that the administration set up to validate the initial determination that a detainee deserved to be labeled an "enemy combatant."

    The military assigns a "personal representative" to each detainee, but defense lawyers may not take part. Nor are the tribunals required to disclose to the detainee details of the evidence or witnesses against him - rights that have long been enjoyed by defendants in American civilian and military courts.

    Under the 2005 Detainee Treatment Act, detainees may appeal decisions of the military tribunals to the District of Columbia Circuit, but only under circumscribed procedures, which include a presumption that the evidence before the military tribunal was accurate and complete.

    In the years-long debate over the treatment of detainees, some critics of administration policy have asserted that those held at Guantánamo have fewer rights than people accused of crimes under American civilian and military law and that they are trapped in a sort of legal limbo.

    The detainees at the center of the case decided on Thursday are not all typical of the people confined at Guantánamo. True, the majority were captured in Afghanistan or Pakistan. But the man who gave the case its title, Lakhdar Boumediene, is one of six Algerians who immigrated to Bosnia in the 1990's and were legal residents there. They were arrested by Bosnian police within weeks of the Sept. 11 attacks on suspicion of plotting to attack the United States embassy in Sarajevo - "plucked from their homes, from their wives and children," as their lawyer, Seth P. Waxman, a former solicitor general put it in the argument before the justices on Dec. 5.

    The Supreme Court of Bosnia and Herzegovina ordered them released three months later for lack of evidence, whereupon the Bosnian police seized them and turned them over to the United States military, which sent them to Guantánamo.

    Mr. Waxman argued before the United States Supreme Court that the six Algerians did not fit any authorized definition of enemy combatant, and therefore ought to be released.