While I agree some cases may be like that, Law of War isn't very complex stuff and it is typically pretty easy to know whether an order is lawful or not (i.e., is a person or thing a lawful target or is it civillian in nature, etc.) The scenario outlined in the comment below about refusing Trumps orders wouldn't be interpreted by a low ranking grunt, but between much higher eschelons who will have access to an entire team of lawyers to determine legality.
While I agree some cases may be like that, Law of War isn't very complex stuff and it is typically pretty easy to know whether an order is lawful or not (i.e., is a person or thing a lawful target or is it civillian in nature, etc.) The scenario outlined in the comment below about refusing Trumps orders wouldn't be interpreted by a low ranking grunt, but between much higher eschelons who will have access to an entire team of lawyers to determine legality.