The Justice Department said Friday it will fight a judge's ruling that banned the department from interfering with Oregon's voter-approved law that allows doctors to help terminally ill people kill themselves.

A judge in Oregon ruled in April that the department lacks the authority to overturn the law, the only one of its kind in the nation.

Justice Department lawyers filed paperwork Friday on their plans to appeal. The department did not explain the grounds for the appeal.

U.S. District Judge Robert Jones had said Oregon voters twice endorsed the law and "have chosen to resolve the moral, legal and ethical debate on physician-assisted suicide for themselves."

Jones said Attorney General John Ashcroft was wrongly trying to "stifle" nationwide debate on the issue. He challenged the law in November.

It had been approved by voters in 1994 and 1997, and allows the terminally ill to request a lethal dose of drugs if two doctors confirm they have less than six months to live and the patients are mentally competent to make the request. The patients must take the fatal dose by themselves.

State health officials say at least 91 people, most suffering from cancer, have killed themselves using the law.