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)
Okay, that actually seems like quite a good isolation of the correct empirical cluster. Presumably guided missiles fall under the 'not allowed' category there, as you don't know what path they'll follow under surprising circumstances.