The state of Oregon is challenging U.S. Attorney General John Ashcroft's authority to limit the practice of medicine in the state by attempting to bar physician-assisted suicides.

It sued the federal government Wednesday over a directive that essentially blocks Oregon's Death with Dignity Act.

On Tuesday, Ashcroft put the country's only law permitting assisted suicides on hold by serving notice on Oregon doctors that their licenses to prescribe federally controlled medicines — considered essential to physicians' work — will be revoked if they participate.

Oregon Attorney General Hardy Myers also filed a motion Wednesday seeking to temporarily prevent the government from implementing the order barring doctors from prescribing controlled substances to hasten the deaths of terminally ill patients.

"Ultimately, what we're seeking to do is waylay the federal government from illegally interfering in the practice of medicine in Oregon," said Kevin Neely, a spokesman for Myers.

Ashcroft's order does not call for criminal prosecution of doctors. And it does stipulate that pain management is a valid medical use of controlled substances.

Right-to-die groups and other supporters of the Oregon law were angry that Ashcroft reversed the June 1998 order by his predecessor, Janet Reno, who prohibited federal drug agents from moving against doctors who use Oregon's law.

"Fundamentally, the actions of the U.S. attorney general take away the right of the state to govern the practice of medicine," Neely said.

The law was a citizen's initiative first passed by Oregon voters in November 1994 with 51 percent in favor.

In November 1997, a measure asking voters to repeal the Death with Dignity Act was placed on the general election ballot. Voters rejected the measure by a margin of 60 percent to 40 percent, retaining the assisted-suicide law.

At least 70 terminally ill people have ended their lives since it took effect in 1997, according to the Oregon Health Division. All have done so with a federally controlled substance such as a barbiturate.

Under the law, doctors may provide — but not administer — a lethal prescription to terminally ill adult state residents. It requires that two doctors agree the patient has less than six months to live, has voluntarily chosen to die and is able to make health care decisions.

Unless an injunction is granted, assisted-suicide advocates and politicians say the law is probably on hold because doctors are not likely to run the risk of federal sanctions.

The Associated Press contributed to this report.