RENO ? The nation’s drug czar said Nevada’s ballot issue to legalize possession of marijuana is ludicrous, and that the measure’s supporters are relying on distortions and voter naivete.

“This is a con and it’s insulting to the voters of the state in which it is presented,” John P. Walters said Friday at a news conference.

“We have a momentous decision in this state. We saw the problem that marijuana was massively underestimated in the public mind and if we didn’t do anything it would grow,” he said. “That’s why I came.”

Nevada’s measure would allow adults to possess up to three ounces of marijuana that could be sold and taxed in state-licensed smoke shops.

“This is the most extreme ballot issue they’ve done so far,” he said. Gesturing to three ounces of marijuana in three sandwich-sized bags, he added, “That’s enough to make 250 cigarettes. That’s not personal use.”