GUANTANAMO BAY NAVY BASE, Cuba — A Navy judge on Wednesday rejected a bid by Osama bin Laden's driver to have his charges dismissed because, his lawyers claimed, they did not exist as war crimes at the time of his November 2001 capture in Afghanistan.

Lawyers for Salim Hamdan, 37, accused of material support for terror and conspiracy, had asked the judge to dismiss his case, invoking the constitutional right against ''ex post facto'' application of law.

Congress defined the charges as war crimes in the 2006 Military Commissions Act that set up the Guantanamo war court, where so far 20 detainees here face possible charges. Seven could be executed, if convicted, although not Hamdan, for whom the maximum punishment is life in prison.

''The government has shown, by a preponderance of the evidence, that Congress had an adequate basis upon which to conclude that conspiracy and material support for terrorism have traditionally been considered violations of the law of war,'' Navy Capt. Keith J. Allred, a judge, wrote in the six-page ruling.

Defense lawyers called the decision a marginal victory because, as they interpreted it, Allred agreed to consider their ex post facto argument as a U.S. constitutional issue — before he rejected it.

They plan to argue other constitutional challenges this week, in a bid to stop Hamdan's trial before a jury of military officers, slated to begin Monday.

Hamdan's defense lawyers also forwarded the military judge's ruling to a federal court in Washington, which is to rule Thursday or Friday on whether to stop the war court proceedings.