Perhaps Lt Watada is LEGALLY wrong in the U.S. military's court of "justice", but he appears to be ETHICALLY right!
If your commanding officer tells you to shoot women and children and you do it, you may be LEGALLY correct, but how can you live with yourself, assuming you have some notion of ethics?
In my mind, ETHICS trumps LAW (which represents the majority or the politically powerful). In WW2 Germany, it was the "law" to exterminate people (incl women & children) because they were members of an ethnic group. Should ethics not trump law?