(Marcio Jose Sanchez/AP Photo)

San Franciscans may be forced to wear clothes outside of their homes and some nude activists aren't pleased.

City lawmakers are scheduled to vote Tuesday on an ordinance that, if passed, would make it illegal for anyone over the age of 5 to expose their genitals in public. Exemptions will be made for parades and festivals held under a city permit, according to the ordinance.

A group of activists filed a federal lawsuit against the city on Wednesday, asking that a judge issue a temporary restraining order to stop the vote on Tuesday and provide the court enough time to determine the merits of the case.

One of the plaintiffs, Mitch Hightower, has organized an annual "nude-in" demonstration over the past several years.

"The 'Nude In' is intended to promote a spirit of tolerance, peace and fellowship among the attendees," the lawsuit said, claiming that if enacted, the ordinance would violate the constitutional right of free speech.

"It attempts to criminalize nudity even when engaged in for the purpose of political advocacy," the lawsuit said.

George Davis, who ran for mayor in 2007 and District 6 supervisor in 2010, both times as the "nude candidate," joined the suit, claiming he uses nudity "as part of his political expression."

If the ordinance is enacted, first time offenders would be fined $100. The fine increases to $200 if it's the second offense within 12 months. The third time a nudist is caught, they could be slapped with a $500 fine and potentially charged with a misdemeanor.