(CNN) -- San Francisco residents who like to relax around town naked will have to keep their pants on.
The city's Board of Supervisors approved a public nudity ban Tuesday in a 6-5 vote.
As soon as the measure passed, some protesters inside City Hall tore off their clothes. Authorities draped them in blue blankets and led them away.
Supervisor Scott Wiener, who introduced the ordinance, disputed claims that the measure violates freedom of expression.
"We're a city that believes in freedom, and we've always believed in freedom and free expression," Wiener told CNN affilite KGO. "But taking your pants off at Castro and Market and displaying your genitals to everyone, that's not free expression."
But some nudists have filed a lawsuit claiming the ban violates their First Amendment rights.
"Is the First Amendment more powerful and more important than the passions of an intolerant mob and the ambitions of one or more city supervisors? We would contend that it is, and that's what our case is based upon," the nudists' attorney, Christina DiEdoardo, told KGO.
The ban does not apply at "permitted parades, fairs and festivals."
Otherwise, those caught naked in public could face fines of $100 to $500, depending on the number of prior offenses. A person who violates the ordinance three times in a year could also face one year in jail.
CNN's Melissa Gray contributed to this report.