As Israel wages its war against Hamas in Gaza, world leaders have called for international law to be observed. But this emphasis on the rules around the conduct of war falls short of what people imagine. The law is so permissive that Israel's actions might well be within its limits, and even if they aren't, there is no mechanism for the law to be enforced. In this interview, Samuel Moyn argues that a focus on humane warfare can be counterproductive, and that international law is impotent in the absence of a Hobbesian superstate.