Doesn't matter if it was "registered" or not, as long as you aren't a felon, or an illegal alien, you'll be ok. Self defense shootings are a fine line in the judicial system. The person you end up shooting better be threatening you, or has something within their possesion that could do bodily harm to you/others. Easy way: Man breaks in door with knife. You grab .XXX caliber weapon. Man keeps coming at you with knife in hand. You shoot. Man down, call Stanley Steamer to get the shit out of the carpet. Ohh call the police at some point.