I'm not asking whether it's a political question or not. Let me explain in greater detail. You stated:

Below a certain violence level, they are criminals; above that level, they are combatants (albeit probably irregular and not privileged under the GCs).
I have not seen that distinction made before - that a person's status as either a criminal or combatant is determined by "violence level." I understand articles I & II and the AUMF and I have a passing non-lawyer understanding of the various cases and issues - However, none of those, to my knowledge, use "violence level" as the distinguishing factor splitting combatants from criminals.

To put my question another way, where is the threshold between criminal and combatant violence, who/what has the authority to set and/or alter that threshold, and what is the basis for using "violence level" as a threshold in the first place?