The Supreme Court held an intense oral argument yesterday on Oregon's first-in-the-nation law allowing physician-assisted suicide, with the new chief justice, John G. Roberts Jr., sounding skeptical about the state's claim that it can make its own rules without federal interference.

At issue is a 2001 directive by then-Attorney General John D. Ashcroft that threatens punishment of any Oregon doctor who prescribes a lethal dose of federally controlled drugs to help a terminally ill patient end his or her own life. Oregon enacted its law permitting such prescriptions in 1997, and the state says it falls within its traditional prerogative to regulate the practice of medicine.

The Bush administration argues that Ashcroft was within his statutory authority when he declared that Oregon's law is trumped by the federal Controlled Substances Act -- and Roberts, through repeated tough questioning of Oregon's senior assistant attorney general, Robert M. Atkinson, seemed to agree.

Noting that Atkinson had argued that a state could authorize its doctors to prescribe such legal but potentially dangerous drugs as morphine for nontraditional purposes, Roberts asked: "Doesn't that make the uniformity of law enforcement impossible?"

At another point, Atkinson told the court that Congress had established the Controlled Substances Act in 1971 on the understanding that the states had long been "responsible" in their regulation of medical practices.

But, Roberts interjected, Congress "did not anticipate assisted suicide in 1971."

Roberts's questioning provided the first hints, however tentative, of his views on end-of-life issues. They could also imply a difference on federalism between Roberts and the man he succeeded, William H. Rehnquist. Last term, Rehnquist was one of three justices who voted, on grounds of states' rights, to let California uphold its legalization of homegrown "medical marijuana" -- notwithstanding a federal ban. But Roberts sounded yesterday like a supporter of federal authority.

Justice Antonin Scalia, a conservative who voted against the California law, seemed to line up with Roberts. Justice Clarence Thomas, who had voted to uphold California's medical marijuana law, kept his customary silence yesterday.

Justice Sandra Day O'Connor sounded supportive of Oregon's position, just as she had supported California on marijuana. But her vote will not count if the court's opinion is not ready before the Senate confirms her successor.

Justice Anthony M. Kennedy, with a record on the court that is strongly anti-drug and pro-states' rights, seemed conflicted, saying that it was "a hard case."

The court's four most liberal justices, John Paul Stevens, David H. Souter, Ruth Bader Ginsburg and Stephen G. Breyer, seemed sympathetic toward Oregon's position.

Though all four had sided with the federal government on marijuana in California, the law is different in the Oregon case.

Perhaps most important, the court has specifically declared, in a 1997 case that refused to recognize a constitutional "right to die," that the issue should be up to the states.

Ginsburg referred to that yesterday when she noted that "everyone on this court assumed that assisted suicide was a matter for the states."

Solicitor General Paul D. Clement responded that the Bush administration was merely arguing that any assisted suicides would have to be carried out by "alternative methods."

"We're told these methods are less gentle to the patient," Ginsburg objected.

Oregon authorized lethal prescriptions of substances such as barbiturates that have recognized medical uses and are not categorically banned by the federal government -- as marijuana is. More than 200 people have ended their lives under the law.

The Clinton administration declined to oppose it, citing the unclear language in the controlled substances act. Ashcroft, though, likened assisted suicide to drug-related ills that the act specifically addressed, such as addiction, or the risk of suicide that addiction creates.

The case is Gonzales v. Oregon, No. 04-623. A decision is expected by July.

Protestors against physician-assisted suicide gather outside the Supreme Court yesterday.