An employer can not force somebody to do something. In other words they cannot lock them in or make them do something through some kind of compulsion, but the employer can ask the employee to stay later. The employee could say no and the employee could say yes. The issue is, does the employee want to retain that employment relationship and does the employer want to continue to retain that employee? Business conditions may be such that the employer needs the employee’s assistance, but the employee’s free to say no and the employer then can consider that as to whether or not they want to retain that employee or if they want to promote that employee.