Say the words "I like guns" anywhere today and you'll be treated with all the respect kindness those accused of being witches were in the Dark Ages, heretics during the Inquisition and so on.
CBSA, RCMP, etc take all the items under dispute as to if they are guns or replicas and so to highest spot in the Hawaii and toss them into a volcano.
If they float above the magma they're OK to posses and are returned to the owner. If they sink and melt they were prohibited. Additional punishments may be assessed at that point also.