WASHINGTON – Lawyers for dozens of Guantanamo Bay detainees asked a federal appeals court yesterday to declare a key part of President Bush’s new military trials law unconstitutional.

The detainees’ lawyers challenged the military’s authority to arrest people overseas and detain them indefinitely without allowing them to use the U.S. courts to contest their detention.

Bush gave the military that authority last month when he signed a law that sets up special commissions to hold trials for foreigners designated as “enemy combatants.” Bush hailed the law as a crucial tool in the war on terrorism and said it would allow prosecution of several high-level terror suspects.

In written arguments, attorneys for more than 100 detainees who would be locked out of the regular judicial system asked the U.S. Court of Appeals to let the detainees keep their legal challenges going in civilian courts.

“Persons imprisoned without charge must retain the right to obtain a court inquiry into the factual and legal bases for their imprisonment,” they wrote.

This argument echoes a Supreme Court ruling in June in which the justices ruled that the Bush administration’s system for trying enemy combatants violated U.S. and international law. Within weeks, the president persuaded Congress to pass a law setting up military commissions and barring detainees from using the civilian court system.

Shortly after the law was signed, the Justice Department told hundreds of detainees that their cases in the U.S. courts had been rendered moot.

Even if the judges decide not to declare the law unconstitutional, attorneys offered a creative way for the court to keep the case alive. They suggested the judges rule that the law doesn’t mean what the Justice Department thinks it means – because if it did, it would be unconstitutional.