That's exactly my point. I'm asking whether or not an employer should write a contract that specifically states the employee should modify their behaviour to ensure things aren't discovered later - namely that the employer knew (or at least "was informed") that illegal things were going on. I don't think they should. If my employer wanted me to sign something that said "If you see things happening that you believe might be illegal, please keep quiet about it because you don't understand the law" I think I ought to say no.