The ruling marks the first court decision to declare a part of the post-Sept. 11 anti-terrorism statute unconstitutional, said David Cole, a Georgetown University law professor who argued the case on behalf of Humanitarian Law Project.

In a ruling handed down late Friday and made available Monday, U.S. District Judge Audrey Collins said the ban on providing "expert advice or assistance" was impermissibly vague, in violation of the First and Fifth Amendments.

John Tyler, the Justice Department attorney who argued the case, had no comment and referred calls to the department press office in Washington. A message left there was not immediately returned.

The case before the court involved five groups and two U.S. citizens seeking to provide support for lawful, nonviolent activities on behalf of Kurdish refugees in Turkey.

Humanitarian Law Project, which brought the lawsuit, said the plaintiffs were threatened with 15 years in prison if they advised groups on seeking a peaceful resolution of the Kurds' campaign for self-determination in Turkey.

The judge's ruling said the law, as written, did not differentiate between impermissible advice on violence and encouraging the use of peaceful, nonviolent means to achieve goals.

"The USA Patriot Act places no limitation on the type of expert advice and assistance which is prohibited and instead bans the provision of all expert advice and assistance regardless of its nature," the judge said.

Cole declared the ruling "a victory for everyone who believes the war on terrorism ought to be fought consistent with constitutional principles."