Unethical, morally questionable, in poor taste, impolite, unprofessional, or underhanded is pretty normal and you can find it in every job in every industry and you might not even realize without the benefit of hindsight that what you did was any of those things. But illegal feels different when it happens, even if you don't know exactly the law something will be off. You'll be apprehensive in a way you weren't before, people around you will act different, this little pit of anxiety will form in your stomach even if you haven't done it yet.