“[i]n a context where we cannot assume that everyone present is a combatant, then we have to figure out who is a combatant and who is not.
Funny, our enemies don't seem to have that problem. :P
If you are referring to terrorists, they generally claim that democracy or whatever makes us all complicit, IIRC.
This rather serious report should be of interest to LW. It argues that autonomous robotic weapons which can kill a human without an explicit command from a human operator ("Human-Out-Of-The-Loop" weapons) should be banned, at an international level.
(http://www.hrw.org/reports/2012/11/19/losing-humanity-0)