SAN FRANCISCO – Four protesters were arrested in the buff as they took to the steps of San Francisco City Hall in a brazen challenge of the city’s ban on public nudity Friday, the first day it went into effect.

One woman and three men were taken into custody as about a dozen other protesters in various states of undress paraded around with slogans painted on their bodies, holding up signs with messages such as “The Human Body is Beautiful.”

In December, the Board of Supervisors voted 7-4 in favor of the ordinance, which prohibits exposed genitals in most public places, including streets, sidewalks and public transit.