Lethal autonomous weapons and jus ad bellum proportionality

Abstract

Much of the debate over the moral permissibility of using autonomous weapons systems (A WS) focuses on issues related to their use during war (jus in bello), and whether those systems can uphold the principles of proportionality and distinction. This essay, however, argues that we ought to consider how a state’s portended use of AWS in conflict would affect jus ad bellum principles, particularly the principle of proportionality. The essay argues that even the clearest case of a defensive war against an unjust aggressor would prohibit going to war if the war was waged with A WS. The use of A WS to fight an unjust aggressor would adversely affect the ability for peaceful settlement and negotiations, as well as have negative second-order effects on the international system and third party states. In particular, the use of A WS by one state would likely start and arms race and proliferate weapons throughout the system.