This is something that is controlled by state law, so it varies from state to state. In some states you are required to retreat if possible and you can only shoot if that is not possible. So if a thug enters your home you have to run out of the house if you can. That's stupid; you have to leave while the crook remains in
your house.
This is what the Mississippi law says:
"SB 2426 states that if a criminal breaks into your home, your occupied vehicle or your place of business, you may presume he is there to do bodily harm and may therefore use any force necessary against him.
Mississippi courts have consistently recognized the "stand your ground" principle - both inside and outside the home - since the late 1800s. SB 2426 would codify such court precedent into law.
Furthermore, the “Castle Doctrine” law provides protection from criminal prosecution and civil litigation for those who defend themselves from criminal attack."
http://www.nraila.org/CurrentLegislation/Read.aspx?ID=2096Seems reasonable to me