This regulation is unenforceable and everyone knows it. There is no way that all ammo in the hands of citizens can be checked for legality. This bill doesn't have a chance, IMHO.
Oh, but it is. You don't bother to check the populace for compliance. It's just that -- bingo! -- when you pick somebody for something else, here's another nice, juicy felony you can stick him with.
Like so much unreasonable legislation, many of us have too much at stake to break it, but criminals do not. It's another "disarming good citizens" measure.