GUANTANAMO BAY NAVAL BASE, Cuba - A federal judge has ordered a civilian court hearing for Osama bin Laden's driver, a landmark ruling that throws into question the Bush Administration's plans to bring alleged terrorists to justice through military tribunals by denying them prisoner-of-war status.

The Justice Department said it would seek an immediate stay of the Monday ruling by U.S. District Judge James Robertson and file an appeal.

The judge, ruling from Washington, halted the pretrial proceedings of Salim Ahmed Hamdan, 34, of Yemen, after his lawyers filed a petition challenging his status as an alleged enemy combatant.

Hamdan was taken captive in Afghanistan and held there for six months before being transferred to the Guantanamo Bay Naval Base, where he claimed to have been kept in solitary confinement for eight months.

Hamdan - charged with conspiracy to commit war crimes, murder and terrorism - says he never supported terrorism. He was to have been the first detainee tried, on Dec. 7.

It was the first time a federal court halted legal proceedings before U.S. military commissions, resurrected from World War II, at Guantanamo Bay. No trials have been held, although tentative trial dates have been set for three other detainees.

The judge rejected the U.S. government's contention that Hamdan and other detainees are not prisoners of war but enemy combatants, a classification affording fewer legal protections under the Geneva Conventions. Hamdan was declared an enemy combatant last month by a review tribunal during a hearing from which his lawyer was barred.

"Unless and until a competent tribunal determines that petitioner is not entitled to protections afforded prisoners of war under Article 4 of the Geneva Convention ... he may not be tried by military commission ... ," Robertson said in his ruling.

"There is nothing in this record to suggest that a competent tribunal has determined that Hamdan is not a prisoner of war under the Geneva Conventions."

The court also ruled that unless the military commission guidelines are changed to conform to the Uniform Code of Military Justice, Hamdan cannot be tried by the commissions.

If the Guantanamo detainees are ultimately determined to be prisoners of war entitled to trial by court martial, they would have available to them different standards for evidence and could appeal up to the Supreme Court.

Justice Department spokesman Mark Corallo said the government would appeal the ruling on the grounds that the Geneva Conventions do not apply to members or affiliates of al-Qaida.

"We vigorously disagree with the court's decision, and will seek an emergency stay of the ruling and immediately appeal," Corallo said in a statement on the department's Web site.

"We believe the President properly determined that the Geneva Conventions have no legal applicability to members or affiliates of al-Qaida ... ."

He claimed the ruling "put terrorism on the same legal footing as legitimate methods of waging war."

Hamdan's civilian defense attorney, Neal Katyal, said the ruling could set precedent for all the detainees.

Richard Samp, chief attorney for the conservative Washington Legal Foundation, said he expected the administration to win its appeal. "The president's constitutional authority to try war criminals before military commissions has been well-established through our history," he said.