红州蓝州开枪的区别也很大, stand your ground, castle doctrine，duty to retreat

Types of Self-Defense Laws

Although some states use a blend of doctrines, self-defense laws generally fall into the following three categories:

1. Stand Your Ground: No duty to retreat from the situation before resorting to deadly force; not limited to your home, place of work, etc.
2. Castle Doctrine: No duty to retreat before using deadly force if you are in your home or yard (some states include a place of work and occupied vehicles)
3. Duty to Retreat: Duty to retreat from a threatening situation if you can do so with complete safety