and return any they already took in the wake of Hurricane Katrina.
If they don't have receipts from the confiscation (they don't as none were given) or from when they bought the weapons, but they bought them from a federally licensed dealer, then the dealer will have sales records, including the 4473 that they filled out when they bought the weapons.
Be really ironic if "gun registration" was used to protect the rights of gun owners, wouldn't it. :)