I've been waiting for a test case for this for awhile, as is, the law is completely unenforceable. Aside from obvious post ban mags like pmags and ones stamped with "le/mil only" everything is pretty much fair game until some DA decides to make you prove what you have is actually pre-ban. People always say its up to the state to prove they are post-ban, but we all know the extent these people will go to bring someone up on firearms charges.
When faced with huge legal bills to defend themselves, expect them to plea out on the charges and settle for PP status and a slap on the wrist.