Jus in Bello: AI is not just another weapon

Unlike most other weapons, those which incorporate AI into their systems have the potential, and often the reality, of replacing the human decision maker in lethal contexts. Whereas the traditions of Just War contain within them distinct moral considerations which, in the context of war using conventional weapons, are for the guidance of the human user, when AI is introduced, this moral capacity cannot be taken for granted. Here, we discuss the necessity of introducing the moral character of the user into the design and use of AI-driven weapons, since neither the market in arms nor the tenets of utilitarian reasoning will ensure this. We go on to note the potential for AI to enable weapons systems to be more effective in defensive situations, especially where speed of calculation is key to successful defence, and to AI’s potential to enhance the Just War principles of proportionality and discrimination. However, because the boundary between defensive and offensive usages is permeable, we conclude that no AI application in combat can be regarded as ‘just another weapon’ and that the place of the human decision maker in, or on, the loop requires constant consideration.