An international public debate over the law and ethics of autonomous weapon systems (AWS) has been underway since 2012, with those urging legal regulation of AWS under existing principles and requirements of the international law of armed conflict, on the one side, in argument with opponents who favor, instead, a preemptive international treaty ban on all such weapons, on the other. This Chapter provides an introduction to this international debate, offering the main arguments on each side. These include disputes over defining an AWS, the morality and law of automated targeting and target selection by machine, and the interaction of humans and machines in the context of lethal weapons of war. Although the Chapter concludes that a categorical ban on AWS is unjustified morally and legally — favoring the law of armed conflict’s existing case-by-case legal evaluation — it offers an exposition of arguments on each side of the AWS issue.

Note: This Chapter was principally drafted in 2015 and reflects developments only up to that point. The Chapter appears in final form in the Oxford Handbook of Law, Regulation, and Technology (July 2017). This final galley pdf appears by permission of OUP.