John Walters, the federal drug czar, has been striving for a delicate balance during his recent visits to Nevada. On the one hand, he has made it clear that he wants Nevadans to vote against an initiative on Tuesday's ballot that would legalize private marijuana use by adults.

"This is a con, and it's insulting to the voters of the state in which it was presented," Walters said in Reno last month. He dismissed supporters of the initiative, which would allow licensed marijuana sales and possession of up to three ounces, as "goofballs."

On the other hand, Walters has tried not to come across as too heavy-handed, lest he antagonize an electorate that seems to be almost evenly split on the issue. "People have a right to make their own decisions," he said in Las Vegas last summer. He added that if Nevadans decide to legalize pot, "I don't believe you'll see federal officials coming into [Nevada] to enforce possession laws."

The implication that the federal government would let Nevada go its own way is hard to believe when you consider how the Clinton and Bush administrations have responded to more modest marijuana policy reforms. A week before Election Day, a U.S. appeals court rebuked the federal government for threatening to put doctors out of business if they dared to recommend marijuana as a medicine.

The medical use of marijuana is permitted by nine states (including Nevada), in all but one case as a result of ballot initiatives. Far from conceding that people—whether voters, physicians, or patients—"have a right to make their own decisions," Walters and his predecessor, Barry McCaffrey, have insisted that doctors who recommend cannabis should lose their federal prescription licenses.

Responding to a challenge brought by California patients and physicians, the U.S. Court of Appeals for the 9th Circuit rejected that threat as an unconstitutional infringement on freedom of speech. In a concurring opinion, Judge Alex Kozinski noted that "the federal government's policy deliberately undermines the state by incapacitating the mechanism the state has chosen for separating what is legal from what is illegal," since California allows marijuana use only by patients who have a doctor's recommendation.

"In effect," Kozinski wrote, "the federal government is forcing the state to keep medical marijuana illegal." Such an imposition, he suggested, amounts to unconstitutional "commandeering" in violation of a state's prerogatives under the 10th Amendment. That kind of strong-arming is especially suspect, he said, when "Congress legislates at the periphery of its powers."

The federal drug laws are ostensibly based on Congress's authority to "regulate Commerce...among the several States." Yet as Kozinski noted, "medical marijuana, when grown locally for personal consumption, does not have any direct or obvious effect on interstate commerce."

Last year the U.S. Supreme Court ruled that federal law does not allow a "medical necessity" defense against marijuana charges. In other words, the fact that marijuana is the only effective way for someone to obtain relief from debilitating nausea or agonizing pain does not protect him from federal prosecution.

But the Court did not address the question of whether the federal prohibition of medical marijuana violates the 10th Amendment or exceeds Congress's authority under the Commerce Clause. Those issues, among others, are raised in a lawsuit filed last month by two California patients who are challenging the Drug Enforcement Administration's crackdown on organizations that distribute marijuana to sick people.

Both the unsuccessful attempt to gag doctors and the (so far) successful effort to shut down medical marijuana clubs indicate that the federal government is reluctant to let states experiment with new drug policies, as they have every right to do under our constitutional system. Local resentment of this interference is so strong that San Franciscans are likely to approve a measure on Tuesday that would ask the city to explore the possibility of growing and distributing medical marijuana. An Arizona proposition that would establish a state distribution system also has attracted substantial support.

By contrast, Nevada's initiative (which has to be approved by voters twice because it would amend the state constitution) would allow private sales, not just to patients but to anyone 21 or older. Could John Walters, who can't stand the idea that sick people might use marijuana to get relief from their symptoms with state approval, learn to live with such a system, as he suggests? I hope we get a chance to find out.