a little term called treason. The punishment for treason is death. I know, I know...the dude wasn't convicted in absentia. Unfortunately, highly complicated drone attacks like that are very time sensitive. If the order wasn't given at the time, the douche could have escaped.
Also, there wasn't anything alleged about the guy. He was a high ranking al quaeda official and one of their top recruiters. Please stop with the ridiculousness. Have a good evening.