A "Castle Doctrine" (also known as a Castle Law or a Defense of Habitation Law) is an American legal concept derived from English Common Law, which designates one's place of residence (or, in some states, any place legally occupied, such as one's car or place of work) as a place in which one enjoys protection from illegal trespassing and violent attack. It then goes on to give a person the legal right to use deadly force to defend that place (his/her "castle"), and/or any other innocent persons legally inside it, from violent attack or an intrusion which may lead to violent attack. Within the legal paradigm, therefore, it functions as a type of justifiable homicide.

Other states have a "stand-your-ground law," which expressly relieves the home's occupants of any duty to retreat or announce their intent to use deadly force before they can be legally justified in doing so to defend themselves. In states where Castle Law is included as a part of a larger personal-self-defense law, there may be a duty to retreat if the altercation happens in a place outside the home, even though there is no duty to retreat if the altercation happens at the home.

States with a Castle Law and a stand-your-ground provision include: Alabama, Alaska, Arizona, Connecticut, Florida, Hawaii, Idaho, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maine, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, North Carolina, Pennsylvania, Rhode Island, Texas, Tennessee and Utah. States with no known Castle Law include: Iowa, Maryland, West Virginia and Ohio. -- source wikipedia.org