Washington ? The first military commission trial at Guantanamo Bay, Cuba, was halted Monday after a federal judge here ruled the proceedings invalid under U.S. and international law — dealing a blow to the legal process set up by the Bush administration to handle accused terrorists.

The case against Salim Ahmed Hamdan was suspended after U.S. District Judge James Robertson ruled the Yemeni had been denied due process.

The ruling affects all of the nearly 500 detainees from Afghanistan now at Guantanamo.

Robertson ruled that the Bush administration had not followed a lawful procedure in declaring Hamdan an “enemy combatant” who was not entitled to protections and privileges under the Geneva Convention. The “combatant status review tribunals” — used by the Pentagon to decide whether to hold detainees — are not a “competent” court to make such a determination, Robertson said. And the military commission process, which prosecutes detainees using secret evidence and unnamed witnesses, “could not be countenanced in any American court,” the judge ruled.

“The government has asserted a position starkly different from the positions and behavior of the United States in previous conflicts, one that can only weaken the United States’ own ability to demand application of the Geneva Conventions to Americans captured during armed conflicts abroad,” Robertson wrote.