Just Security schools us on international law and points out the US government’s rationale for the assassination-by-drone of Anwar al-Awalaki (no less his teenage son at a later date) was illegitimate for a number of reasons, including AQAP’S lack of “central command and control”:
Under International Humanitarian Law, or IHL, an armed conflict only exists if hostilities are taking place between a state and another state, or between a state and a clearly defined non-state group with a central command and control structure. To constitute an armed conflict, hostilities must reach a level of intensity that is more than sporadic acts of terrorism…"
Just Security, You Can’t Have an “Associated Force” with No Core
The Atlantic, from October 2012 on “How Team Obama Justifies the Killing of a 16-Year-Old American"… al-Awalaki’is teenage son… "…a senior adviser to the president’s campaign suggests he should’ve "had a more responsible father."