See post #45 - all replica weapons (guns, etc) are what the laws prohibit or restrict in some states... not specific items or toys.
If Customs were targeting a specific item (like MP Megatron when it came out), it would only have been an internal memo/alert to look out for a specific x-ray image, as that toy was in robot mode, and they don't open any package until it has been scanned, swabbed or sniffed first.