The city temporarily shut down performances of "Naked Boys Singing!" in August 2005 while it considered the Milwaukee Gay Arts Center's application for a theater permit. The group later received a permit and reopened the show.

Larry Dupuis, legal director for the American Civil Liberties Union of Wisconsin, which is handling the case, said the city's enforcement seemed unusually zealous, even given the musical's content.

"I think the title made it kind of controversial," Dupuis said. "But of course, `The Full Monty' has nudity in it, and that doesn't get it threats to shut it down."

The lawsuit, filed Monday, says the city ordinance is unconstitutional because it gives officials "unbridled discretion" over when permits must be obtained and how applications will be handled. It also says the law could be used to restrict certain viewpoints.

Eileen Force, a spokeswoman for Mayor Tom Barrett, declined to comment on the lawsuit, and a call to the office of City Attorney Grant Langley rang unanswered Monday afternoon.

Dupuis said few, if any, other nonprofit theater groups have been required to get permits from the city.