Whatever you decide to do, you really should report the violation of the law in some way to one of your superiors, and do it in a documented, traceable fashion (email).
Either way things can't go back to the way they were. You're either getting fired, or you're going to choose to leave. This means changes are coming. So you've got to take charge of how your life is going to change.
Another thought- it's possible that your supervisor's manager is aware of the action being taken against you. You might be able to get better advice talking to someone in a different reporting chain if you can find them.
Whether that would actually help here and whether such markings have any weight in whatever legal system the OP is operating within are different questions, of course.