This is not legal advice, if you want same, contact a local lawyer.
As a non citizen of PRK, the state has NO authority over anyone who is not IN the state. Limited authority over persons who committed crimes INSIDE the state is reflected in extradition of suspects from other states.
It would be like PRK passing a law that no vehicle NOT equipped with PRK mandated smog equipment can be operated anywhere, even outside PRK. You can have a direct oil injector on your tailpipe and you needn't fear prosectution by PRK. They have no jurisdiction over you.
It is illegal to sell or bring in standard cap mags. Translation, if one is HERE and does so, out come the cuffs, either at the scene of the transaction or at the border where the moron brought them across.
Hypothetical, an otherwise unremarkable package sent from outside the state majically breaks open and whoever sees what's inside knows what they are and calls the authorities.
The adressee is up shit creek, but the person who unwisely put their REAL return addy on it, showing that they live in another state, is not under the jurisdiction of PRK.
This is IMHO, of course, and I would return the money order and POST next time that you won't ship where prohibited.
It is NOT a federal issue, so please don't post that the BATF or some other Fed agency has the time or inclination to enforce STATE law, as they have no jurisdiction to do so.