Although the Illinois Antitrust Act says “no person shall be authorized to maintain a class action in any court of this state for indirect purchasers asserting claims under this act, with the sole exception of this state’s attorney general,” Lawrence Hatchett — a dental patient who alleged he suffered indirect antitrust injuries under the IAA because of a price fixing conspiracy by three companies that dominate the market in providing equipment and supplies to dentists — relied on Federal Rule of Civil Procedure 23 in …