The appeal from Attorney General John Ashcroft had been expected since May, when a lower court ruled the federal government could not punish Oregon doctors who prescribed lethal doses of federally controlled drugs.
Oregon voters approved the law and since 1998 more than 170 people have used it to end their lives. Most had cancer.
The Bush administration has argued that assisted suicide is not a "legitimate medical purpose" and that doctors take an oath to heal patients, not help them die.
While not as prominent as abortion, the issue is an important one for conservative Christians, who helped President George W. Bush win a second term last week. The government waited until Tuesday, the final day possible, to file paperwork at the high court.
Oregon's law, known as the Death With Dignity Act, lets patients with less than six months to live request a lethal dose of drugs after two doctors confirm the diagnosis and determine the person is mentally competent to make the request.
Paul Clement, acting solicitor general, said in the appeal that the law cannot stand because it conflicts with the federal government's powers.
The Supreme Court will likely decide early next year whether it will hear the case. The court has been hearing cases now with just eight members, because Chief Justice William H. Rehnquist is being treated for thyroid cancer.
The high court has dealt with right-to-die cases before. Justices held in 1997 that while there is no constitutional right to assisted suicide, states may decide the issue for themselves without federal interference.
Oregon is the only state that has a right-to-die law, although leaders in other states have considered laws of their own.
At issue for the court now would be the bounds of a federal law declaring what drugs doctors may prescribe. Traditionally states, not the federal government, regulate medical practices.