War criminal under whose law?
Understand me. "Crime" is a social construct that is specific to whatever country you're in. What's considered a crime in the US isnt a crime in Saudi Arabia, and vice versa.
With that being said, Obama did what he had to do to keep Americans safe. At any given point in time, there are plans underway to attack this country; and the job of the President is to keep the country safe, and at times, that requires hard imperfect choices.