Self defence is not listed as a reason to own a gun in Oz. All our firearms have to be locked in a certified gun safe. If you shot an intruder you would most likely be grilled how you accessed you gun and ammo so quickly! Auto rifles and shotguns are only allowed on a special licence. Handguns are very tightly controlled and I think you have to be a member of a club or a collector to own one but I don't know too much regarding these. Each state may also differ slightly. It is not to difficult to own a type a or b firearm but you have to apply for a purchase permit to buy one which may take 14 days or however long it takes while they do background checks etc.