From today's McClatchy Newspapers article Pentagon Exploring Robot Killers That Can Fire on Their Own:
At Georgia Tech, Arkin is finishing a three-year Army contract to find ways to ensure that robots are used in appropriate ways. His idea is an "ethical governor" computer system that would require robots to obey the internationally recognized laws of war and the U.S. military's rules of engagement.
"Robots must be constrained to adhere to the same laws as humans or they should not be permitted on the battlefield," Arkin wrote.
Arkin made a video (below) that explains his "Ethical Governor" concept. So... who gets charged with war crimes when killer robots fail "to obey the internationally recognized laws of war"?