Jennifer Gilligan says she wasn't drinking at the party and didn't know other underage people were.

But when Naperville (search) Police pulled up, the 20-year-old and more than a dozen others were ticketed, not for underage drinking, but for simply being at a party where their peers had alcohol.

"I was very upset because I don't drink," Gilligan said.

She isn't the only one complaining about the Chicago suburb's unusual ordinance. So are parents who say they teach their children to be responsible and stay away from alcohol until they reach the legal drinking age of 21 — no matter what their friends are doing. They say police are punishing the wrong group.

It's become such a contentious issue, police have stopped publicizing the names of those ticketed and the city has called for a public hearing in September.

"The ticket is bogus because it gives kids a ticket for choosing not to drink," said RuthAnn Wood, whose 18-year-old son was cited at a graduation party in May but later found not guilty.

Garrison Wood's citation was one of more than 100 police wrote in the first six months of the year under the new ordinance targeting people under 21 who aren't drinking, but who are with underage peers who are. Those cited must appear in court and can be fined $35 and ordered to perform 20 hours of community service.

Naperville, a community of 135,000 named last year by Money Magazine (search) as one of the nation's most desirable places to live, already prohibited minors from attending drinking parties. Last year, the City Council changed the wording to create a specific ordinance to ticket minors at the parties who aren't drinking.

"We're trying to be involved in the situation and recognize the tragic and sometimes horrific outcomes of these underage parties," said Naperville police Lt. Dave Hilderbrand. "We're trying to take a bit more of an ambitious step."

In 20 years of researching problems associated with underage drinking, James Mosher, a research attorney at the nonprofit Pacific Institute for Research and Evaluation, said he hadn't heard of a law like it anywhere else in the country.

Mosher questioned the law's effectiveness — "You don't want to punish young people who have made the decision not to drink," he said — and its legality.

"I think there is a fundamental constitutional problem with it," Mosher said. "I can certainly appreciate the police wanting to have this. But the idea that you have to leave a place because someone is committing a crime and you are not, is fundamentally unfair."

Naperville's city attorney, Frank Cuneo, said minors don't belong at parties with alcohol. "If parents did their jobs, we wouldn't need this ordinance," he said.

Mayor George Pradel said it's the job of city officials to protect the community. "We love our young people, and we want them to have a clear understanding that it's against the law (to drink) and they shouldn't be there," Pradel said.

"It's a deterrent, because young people know if they go to a beer party, they'll have to appear in court."

But RuthAnn Wood said Naperville has gone too far in its commitment to promote a high quality of life. "They have to have perfect, perfect, perfect, and these teenagers are just a thorn in their sides," she said.