The laws vary so much by state, let alone the cities, you need to check into the laws for state and city. May look in the hometown forums on ar15.com. I'm still learning the laws here in colorado, but in Oklahoma, there isnt a 7yd rule or anything of the such. You have to be aproached by leathal force, overwhelming odds(10 guys lets say), or someone known to be convicted of a violent offense(IIRC) to be ok to use lethal force. Still isnt cut and dry, as an over zealous DA will still try to make a name for himself. Out in the liberal northeast, I would go with the assumption they are like canada, no rights to protect yourself, just dial the 911 dial a prayer hotline and hope.
Now I await my stalker to come attack me....