Nudists in famously tolerant San Francisco have lost a bid to block a city ban on nakedness in public places. A federal judge on Tuesday threw out a legal challenge that argued public nudity was akin to political expression.

San Francisco city leaders last month approved the ban on baring it all in streets, public plazas and the transit system to curtail public nudity, which some residents and business owners complained had gotten out of control.

The efforts to clamp down have caused a flap in the city, where men in particular are known to parade naked through the streets of the predominantly gay Castro District.

Some residents say nudists, and specifically a group known as the Naked Guys, have gone too far with their constant presence at a square in the Castro District. But nudists claim they have a right go naked in public and say politicians in San Francisco, which has often celebrated the bizarre and unconventional, should leave them alone.

Four nudist activists sued in November, even before the measure barring public nudity was passed by a slim majority of the Board of Supervisors, saying it would violate their constitutional right to free expression.

However, US District Judge Edward Chen concluded that “nudity in and of itself is not inherently expressive,” and denied the nudists’ request for an injunction blocking the measure, which is due to go into effect on Friday.

Violators face fines of up to $100 (€74) for a first offense and $200 for a second. A third violation can bring a year in jail and a $500 penalty.

“Unlike the burning of a flag, burning of a draft card, or wearing a black armband in protest against the war, public nudity in and of itself is not commonly associated with expression of a particular message,” Judge Chen wrote in his decision.

He also noted that the law allows nudity on beaches and during certain events that require city permits, such as the gay pride parade.

The attorney for the nudists, Christina DiEdoardo, said they were still determining their next step. But she said nudists could mount a renewed challenge once the ordinance goes into effect if they are arrested while protesting the law, since they could then explicitly link their nudity to political expression.

“The judge seemed to issue an open invitation to file an amended complaint,” she said.

A demonstration is scheduled for tomorrow outside San Francisco City Hall.