It fell overboard in a fishing accident.
It would depend on who was in charge of the government at that time (including Judges) they could be "grandfathered" in as legal or you could be ordered to turn them in. that is why voting is important
James, similar has happened and current owners may have their Shockwaves "Grand Fathered" in similar to Pre-Ban weapons of years past. We won't know until that bridge is crossed in actuality.