BERLIN, Conn. — You can leave your hat on.
The rules of naked karaoke are simple: Amateur singers grab a microphone, sans clothing, and belt out tunes in the buff.

Bristol Station Cafe owner Marty St. Pierre says he was just kidding around when he advertised such an event in front of his bar. Then he got volunteers. Lots of them.

“It honestly started out as a joke,” he said. “But there were people signing up, so I just let it run.”

The planned event struck a sour note with the establishment’s neighbors, who called Town Hall to complain. Soon, St. Pierre got a visit from town authorities, who said he could face fines or arrest if he operated the naked musical performance without a permit.

The dispute is now the subject of a lawsuit challenging a town ordinance on sexually oriented businesses. While Berlin doesn’t outlaw such businesses they are required to have permits and meet certain zoning requirements, said Town Manager Richard Haberman.

He said the visit to Bristol Station Cafe was just to warn the business about the ordinance and tell the owners they needed to get a permit, before officials enforced penalties.

“Most business owners say, ‘Oh, thanks,'” Haberman said. “The next thing I know, I got a summons.”

Without a permit, a sexually oriented business can face a fine of up to $100 and an arrest on misdemeanor charges, according to the town’s code. The lawsuit contends the penalties are harsher than towns are allowed to enforce under state law.

State statutes specifically permit towns to issue fines to enforce ordinances. But David E. Koskoff, co-owner of the building since the 1980s and the lawyer who filed the lawsuit, claims that the penalties make noncompliance a crime, and that isn’t permitted under state law.

“Towns are creatures of the state, and they have such powers as the state grants to them,” said Koskoff, a Plainville-based attorney.

He also contends the business isn’t “dirty.”

“You’re not talking about the Bada Bing!” he said, a reference to the strip joint frequented in the television series “The Sopranos.” “Nobody who knows our operation would think that suggestion is anything but funny.”

Mayor Paul Argazzi, who is chairman of the town’s Ordinance Committee, told The Herald of New Britain he thought the regulation was one of the strongest in the state, and sound.

“We had constitutional attorneys look at the ordinance. We drafted it believing it to be constitutional,” he said.

Koskoff’s lawsuit also contends the ordinance “operates as a chilling factor” on constitutional rights of expression, according to court papers.

Berlin has been long-known for its battles with sex businesses. Last month local authorities shut down a swingers club that charged a $60 fee to swap spouses. Employees were charged with 14 counts of violating the sexually oriented business ordinance.

Haberman said Bristol Station Cafe owners haven’t applied for a permit, and he hasn’t reviewed whether they meet all the regulations spelled out in the town code. He said if the business meets all the regulations, he’d approve the application.

The case is due in New Britain Superior Court Nov. 17. In the meantime, St. Pierre hasn’t had the chance to actually host a naked karaoke night, but says he’s hopeful.

The billboard outside his club reads “Are you signed up for Naked Karaoke?'”