The American Civil Liberties Union (search) sued the transit authority in the nation's capital Wednesday, saying its refusal to display paid advertisements that criticize anti-marijuana laws violated free speech rights (search).

The lawsuit, filed in U.S. District Court, says the Washington Metropolitan Area Transit Authority (search) acted unconstitutionally when it declined last week to run the ads at subway and bus stops.

The ads were sponsored by the ACLU and three groups joining the lawsuit: Change the Climate (search), the Drug Policy Alliance (searchand the Marijuana Policy Project (search), which support the use of marijuanblic to know how badly our drug policy has failed, so it is trying to silence Americans who oppose the war on drugs," said Graham Boyd, director of the ACLU Drug Policy Litigation Project (search). "Fortunately, the First Amendment clearly prohibits this kind of blatant viewpoint-based censorship."

The suit challenges a new law that cuts off up to $3.1 billion in federal funds to local transit authorities if they display ads promoting marijuana or drug use.

A spokeswoman for Washington Metro, Lisa Farbstein, said city officials were forced to reject the ads to avoid a loss of at least $85 million in federal aid.

"Given our critical dependency on continued federal funding, we have no choice but to follow the law that Congress passed," she said. "To do otherwise would be a disservice to our customers and the region's taxpayers."

Only the Washington Metro transit authority is named in the lawsuit, but the groups filing it said San Francisco and New York could stand to lose at least $100 million and $75 million respectively if they accept paid ads that are seen as promoting marijuana or other drug use.