WASHINGTON -- In the first ruling of its kind, a federal judge yesterday ordered the speedy release of five Algerian men after concluding that the government didn't have the evidence to hold them for nearly seven years in Guantanamo Bay prison.

The decision by U.S. District Judge Richard Leon, who was appointed by President George W. Bush, was the latest setback for the administration's detention policies and could foretell more court-ordered releases.

Judge Leon, however, allowed the continued imprisonment of a sixth Algerian from the same group, concluding that the Justice Department had sufficient evidence that he was a supporter of al-Qaida.

One of those ordered released was Lakhdar Boumediene, whose appeal to the Supreme Court became the underpinning of a 5-4 decision that gave Guantanamo prisoners the right to challenge their detention in court. Mr. Boumediene, 42, had maintained all along that he was a relief worker with the Islamic Red Crescent.

Judge Leon's decision marked the first time that a lower court has concluded after a habeas corpus hearing that the government lacked evidence to hold Guantanamo detainees as enemy combatants. Now, more than 200 other detainees await similar reviews in Washington's federal court.

Judge Leon said he didn't want his ruling to serve as precedent for upcoming cases. Nonetheless, the decision -- issued by a judge who originally supported the government's position -- is certain to hearten administration critics who think that many detainees are being held in the prison in Cuba without cause.

The men, natives of Algeria who immigrated to Bosnia more than a decade ago, have been imprisoned without charges because the Bush administration claimed that they were enemy combatants in an unconventional war waged by terrorists after Sept. 11, 2001.

While the government said the men had plotted to travel to Afghanistan to fight the United States and its allies, Judge Leon found that the government had offered only unsubstantiated information from a single unnamed source as justification to detain the five men. Bosnian courts and prosecutors had previously cleared the men, but on Jan. 17, 2002, Bosnia handed the men over to the U.S. government, which then shipped them to Guantanamo. According to the detainees' lawyers, U.S. diplomats in Sarajevo had threatened the Bosnian government that if Bosnia failed to detain them, the United States would withdraw from the Balkan country.

On Jan. 29, 2002, Mr. Bush announced in his State of the Union Address that U.S. soldiers "working with the Bosnian government, seized terrorists who were plotting to bomb our embassy." But the government dropped that allegation as soon as the group won court review.

Judge Leon's decision comes as the government is trying to prevent the release into the United States of 17 Chinese-born Muslims, who have been held for nearly seven years, despite being cleared for release by the U.S. military. The detainees, all members of the ethnic Uighur minority, are among a group of more than 60 men inside the prison who have been cleared for release, but who are stuck in limbo because the U.S. government can't find a country that will accept them. The men say they cannot return to China because they will be tortured.

As of yesterday, there were about 250 detainees in Guantanamo, including 17 accused of war crimes. The others are being held as enemy combatants, neither charged with a crime nor approved for release.