THE SUPREME COURT heard oral arguments Wednesday in a case that features one of the most aggressive federal assaults on state policymaking authority in recent history. The attack comes from conservative officials who normally profess states' rights as a kind of creed. Only a few years ago, the Supreme Court declined to acknowledge a federal right to a physician's assistance in ending one's own life, ruling that these agonizing end-of-life questions were the subject of a national debate toward which different states might reasonably take different approaches. To date, one state -- Oregon -- has authorized physician-assisted suicide for terminally ill patients; its voters strongly supported ballot initiatives to allow a narrow right to die under limited circumstances.

You might think this is federalism at its best: one state experimenting with a controversial policy for which much of the country remains unready. If it lessens pain while giving the dying more control over the circumstances and time of their deaths, other states might emulate it; if it serves to implicate doctors in death, rather than healing, that will be instructive, too. But the Bush administration stepped in to block the Oregon law, which allows physicians to prescribe (but not administer) lethal doses of federally regulated painkillers. Citing federal drug law, then-Attorney General John D. Ashcroft determined that assisting in death was not a "legitimate medical purpose," so the Drug Enforcement Administration would go after doctors who acted under Oregon's statute. Two lower courts have batted down the Justice Department, but the administration appealed. The notion of federalism -- that is, sovereignty shared between federal and state government -- has little meaning if the Supreme Court approves what the administration has done here.

The case is fundamentally unlike recent controversies over the scope of Congress's power to regulate interstate commerce. If Congress wants to ban assisted suicide, it clearly has the power to do so. But it has chosen not to get involved. The administration leans on federal drug laws that are only remotely relevant. Their purpose, after all, was not to regulate the practice of medicine, which is traditionally the province of the states, but to prevent the sale and abuse of drugs for recreational purposes. What constitutes legitimate medical practice, absent some specific congressional guidance, should be a question of state law.

It would be a bait-and-switch if the court, having specifically reserved this question for state experimentation, now offers no protection to the state that took up its invitation. Whatever one thinks of Oregon's law, it does not violate anyone's federal constitutional or civil rights; nor does it conflict with federal law unless that law is twisted beyond reasonable recognition. Under such circumstances, the people of Oregon should be entitled to govern themselves.