The Ninth Circuit federal appeals court upheld the only law in the nation that authorizes doctors to assist terminally ill patients to end their lives, in a landmark directive for state control over medical care.

Oregon’s Death With Dignity Act came about from a 1994 voter initiative. Doctors may prescribe adults with incurable diseases who are likely to die in six months, but not administer them. About 30 people a year have ended their lives under the law since it became effective in 1997, according to state health records.

In 1997, Attorney General John Ashcroft, then a United States senator from Missouri, urged Attorney General Janet Reno to declare that physician-assisted suicide violated federal law. She declined. When Ashcroft became attorney general in 2001, he reversed Reno’s position. He issued a directive saying that doctors who prescribe such drugs could face federal sanctions and prosecution under the Controlled Substances Act.

A doctor, a pharmacist, several terminally ill patients and the State of Oregon challenged Ashcroft’s directive in 2001. The three-judge panel last week said the Justice Department did not have this power.

“The principle that state governments bear the primary responsibility for evaluating physician-assisted suicide follows from our concept of federalism, which requires that state lawmakers, not the federal government, are the primary regulators of professional medical conduct,” Judge Richard C. Tallman wrote.