Pure Claptrap. No way to enforce it outside of yard to yard searches with metal detectors and then they would miss the majority buried out in the woods.
You’re right about the difficulty enforcing such a law on a national or even widespread basis — but the fact of such a law existing is a danger in itself....
Think of Capone — it was income tax evasion that locked his ass up..
With the law as proposed, the Feds would only have to “find” a single round to render a citizen a felon....