San Francisco lawmakers have given final approval to an ordinance that makes it illegal for residents and visitors to bare their genitals in most public places.

The city's Board of Supervisors voted 7-4 Tuesday in favor of the ban that was introduced in response to a group of nudists that regularly gathers in the city's predominantly gay Castro District.

Mayor Edwin Lee is expected to sign the measure, which is scheduled to go into effect Feb. 1. Opponents already have brought a lawsuit seeking to get it overturned on free speech grounds.

Offenders of the law would face fines and possible jail time for multiple violations.

Exceptions would be made for permitted events such as the city's gay pride parade and the Bay-to-Breakers street race.