U.S. military action fall under the Law of Armed Conflict (LOAC)/Geneva Conventions.
Gives a decent overview of the complexties.
Not to change the subject of the thread.....
But it is not correct that Police and Military have the luxury of impunity. Same basic concepts apply to them as to the general public.
Essentially on a individual soldier/police officer level, you cannot kill a person that is known to not be an immediate threat.
Obviously at a less personal and somewhat more strategic level, there are "targets" and "collateral damage".
However, I think this topic is more narrowly defined down to the individual level.
At this level each person must decide if the conditions and actions they choose are justified.
It is a big decision, a personal one. It is one in which your actions will be viewed either lawful or unlawful by society. It is one in which you must live with your actions based on your own internal values.
I will admit to you that I personally would not consider the legal ramifications of the law of whatever state, country, or what not. To me those are the most unimportant in me choosing the action that I make.
It is more important to me to take action based on whatever moral/value code I have chosen to live by personally.
I have resolved myself to live within and deal with the legal consequences after the fact.
Hopefully I have spent enough time through education, training, and spiritual development to process and reconcile all this prior to the event.
Hopefully the choice I make is in alignment with how the rest of society sees it.
If I do end up in jail or what not....well hopefully I can personally live with the choice I made...knowing deep inside that I made the right choice morally and spiritually!
Watch a "Man for all Seasons" if you want a good lesson on tough choices.
Personally I think this is what defines a warrior or a warrior mentality and separates them from the rest of the flock.
Those that have the capacity, the skill, and the courage to make the right choices in the face of adversity no matter how tough those choices may be.