The lawsuit, filed in federal court in Chicago on Thursday on behalf of the union’s Local 1546, alleges that Treasure Island violated the Worker Adjustment and Retraining Notification Act because all employees will be laid off less than 60 days after they received written notice “on or about” Sept. 26, according to the complaint. Under the law, employers can’t order a “plant closing or mass layoff” until the end of a 60-day period after serving written notice to employees.