If the company chooses not to comply with the law, then I would imagine that either the Illinois department of labor (or its equivalent) could be notifed that the company is violating the law in order to start an investigation, or a group of pilots based in Chicago that feel they have been harmed could file a lawsuit. I'm not a lawyer, nor do I play one on TV, but I would imagine this would have traction in court.
The ball is really in the company's court for them to decide if they want a lawsuit on their hands.