wikipedia | A Castle Doctrine (also known as a Castle Law or a Defense of Habitation Law) is an American legal doctrine that designates a person's abode (or, in some states, any legally-occupied place [e.g., a vehicle or workplace]) as a place in which that person has certain protections and immunities permitting him, in certain circumstances, to use force (up to and including deadly force) to defend against an intruder -- free from legal responsibility/prosecution for the consequences of the force used. Typically deadly force is considered justified, and a defense of justifiable homicide applicable, in cases "when the actor reasonably fears imminent peril of death or serious bodily harm to himself or another". The doctrine is not a defined law that can be invoked, but a set of principles which is incorporated in some form in the law of most states.
The legal concept of the inviolability of the home has been known in Western Civilization since the age of the Roman Republic. The term derives from the historic English common law dictum that "an Englishman's home is his castle." This concept was established as English law by 17th century jurist Sir Edward Coke, in his The Institutes of the Laws of England, 1628. The dictum was carried by colonists to the New World, who later removed "English" from the phrase, making it "a man's home is his castle", which thereby became simply the Castle Doctrine. The term has been used in England to imply a person's absolute right to exclude anyone from his home, although this has always had restrictions, and since the late twentieth century bailiffs have also had increasing powers of entry.