I know this is kind of looked down on but what is stopping anyone from going to a bordering state and buying whatever mags they want and bringing them back home? Obviously Pmags have a date of manufacture stamped on them but as far as I know regular 30 round USGI mags don't have dates, I dont think any other mags have dates on them unless they are printed inside somewhere? What if a date stamp is scratched out and no longer legible?

Is it even specifically against this law to bring them in from another state? They are not being transferred here. What about people who move here, do they just surrender them at the border?