1 Samuel 15:18 and the LORD sent you on a mission, and said, 'Go and utterly destroy the sinners, the Amalekites, and fight against them until they are exterminated.'
Evidently not all killing is murder. Just saying.
But that isn't to say that just because a country passes a law that says “go forth and kill” does not mean that those going forth with that law (which says it is ok) doesn't necessarily make it ok.