One possibility that the article seems to ignore is that in the future, robots may be explicitly programmed to follow laws of war and rules of engagement. There's already been some research into this [1], and some people argue that autonomous robots could eventually be better than humans at following international law in combat. It does seem like a stretch given the present state of AI, but in the future there might be treaties that specify the algorithms that autonomous systems have to implement if they're going to be deployed to combat situations.
[1] http://www.cc.gatech.edu/ai/robot-lab/online-publications/fo...