When a person is outside their home or workplace deadly force to defend yourself is illegal. There is a duty to retreat when outside your home or workplace.
Stand Your Ground Laws are often expansions of the Castle Laws. They address the use of force outside of one's home, place of work, or vehicle. They cover most of the same issues as the castle laws (the places where this law applies, the requirements fro use of deadly force, if there is a duty to retreat, the amount of force that maybe used in defending one's self or others) the main difference is the location. Some states that do not have a technical Stand Your Ground Law have extensive Castle Laws that address locations outside of the home, place of work, etc. The circumstances of the law vary widely from state to state.