The definition of a crime is doing something that is against the law. By holding a fake I.D. you are committing a crime and therefore breaking the law.

Now, if you never use it, chances are you will never be caught for your actions of breaking the law. This doesn't mean that just because you are not caught breaking the law, that you are not in fact breaking the law by the mere possession of the fake I.D. It is a very, very serious offense. And if you are ever stopped by the police and caught with fake I.D., you will be arrested with no questions asked.