and landmines, if you're looking for precedent.
Neither land mines nor pit-traps are "autonomous robotic weapons" of course. But speaking of precedent, there are numerous campaigns to ban land mines (eg. http://www.icbl.org/), for reasons which are rather similar to those advanced in "The Case against Killer Robots".
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)