From my state we can't, if we are legally licensed gun owner, regardless if our life is in danger we would lose our gun and face a judge no questions asked, a lot of people here think you can start pot shotting people if you own a gun.. but its not like that. thats one of the things demonstrated when we sit our gun course
if our life is in danger, we would have to use other means to defend ourselves, another reason is if you shoot someone, you don't know whats behind that person, and depending on how powerful your gun is.. you'd probably take out the neighbours house too lol
if a burglar smacks you, you can smack him back
if a burglar stabs you, you can stab him back
if a burglar tries to kill you, you have the right to take his life away
but one of the things that always gets pumped into your head, is no matter what.. never use your gun in self defence; because when you sit your test, its not for self defence, its for recreational hobby / game hunting, or target shooting
anyways, thats in my state, of course mildly different to other states :)
edit: don't get me wrong, I would love to have an american style self defence law.. would get rid of alot of the cockroaches