> rather than the fact that he went to Yemen and took up arms against the United States while inciting violence against the country.

It is difficult to call it a fact since there was no trial, no due process, nor evidence cited by US government in the killing of its citizen. Perhaps there was secret evidence presented in secret to a secret court, but that's rather grim consolation.

Also the concept of law should absolutely insert itself into matters of foreign military matters. WWI and WWII were both horror shows, Western civilization rightly decided to do their best not to repeat the worst of the atrocities committed therein. You seem all to eager to return to a world where Western governments kill millions without consequence.