According to TMZ, authorities promptly forced Bieber and his entourage to leave, then cited the club owners for serving alcohol to a minor.
"The ticket was issued by the police to Bodi Nightclub for admitting and knowingly having underage persons in the establishment," a rep for the Chicago Department of Business Affairs told TMZ. "Typically the fine for a ticket like this would be $1,000."
The singer will await a court hearing on the matter. No date has been reported.