"Nobody wants to take your guns! Unless you try to obey the law

and tell us you have them, THEN you're screwed!"

The LEAST I can see this going is the SWAT team at the door(assuming they don't just bust in and shoot the dog so as to set an example):
"You're under arrest for having an unregistered assault weapon.  Where is it?"
"I sold it."
"Show us proof you disposed of it as required!"
"Screw you."  Downhill from there.