A television commercial challenging the government's ad campaign linking marijuana use to terrorism will begin airing Thursday in the Washington area.

The ad is a parody of the "Nick and Norm" spots -- sponsored by the White House Office of National Drug Control Policy -- in which two men discuss whether buying marijuana ultimately funds terrorists.

In the spoof, Nick tells Norm the marijuana trade supports violence only because marijuana is illegal. "If I buy a beer, that doesn't support terror, because beer is legal, right?" Nick asks. When Norm agrees, Nick concludes, "So what you're saying is if we make marijuana legal and regulate it like beer, it wouldn't support violence."

Produced by the Washington-based Marijuana Policy Project, which advocates marijuana legalization, the 30-second ad is to air through March 7 on the ABC, CBS and Fox affiliates in Washington at a cost of $20,000.

Tom Riley, a drug policy office spokesman, said the argument is flawed because the same rationale also would support legalizing heroin and cocaine.

"Imitation is the sincerest form of flattery," Riley said of the parody. "Our ads have obviously struck a nerve."

Marijuana Policy Project spokesman Bruce Mirken said the government's campaign is misleading.

"The drug czar has really gone heavily on the anti-marijuana binge with the campaign he's running," Mirken said. "The point is really that marijuana doesn't cause violence, prohibition does."