Indeed, Hathaway and Shapiro have to explain why a treaty signed in 1928 caused wars of conquest to begin to slow only two decades later—after the Axis powers had invaded far and wide and the Red Army had planted itself in Eastern Europe. They claim that the pact, given its momentous nature, took time to win genuine acceptance, and also that it led to the creation of the United Nations, which helped to end wars of conquest after the dust of World War II had settled. But this long chain of causal links—leaving aside for the moment whether they actually connect—undercuts the authors’ effort to single out the pact itself and the idealistic jurists who shaped it.
In fact, when one looks at the history of this period, something like the opposite story makes as much sense. By outlawing war, one might argue, the great powers sought to freeze the territorial gains they had already made. This attempt, in turn, spurred their competitors to grab everything they could. As historians like Adam Tooze have shown, the Axis powers feared that, if they did not gamble on rapid conquest, they would drop forever to the second tier, below the internationalist poseurs who had already seized Africa, Asia, and North America and now pronounced their consciences shocked when others followed suit. If the pact had any direct effect, then, it was this: to spur Germany, Japan, and Italy to grab imperial hinterlands of their own before it was too late.
The Allies prevailed in the end, of course. Yet their victory did not eliminate the hazards of “outlawing” war. Now that making war is theoretically forbidden, many war-makers claim to be doing something else—engaging in self-defense, or policing the commons, or taking military measures that stop just short of war. In the United States, for example, Congress has not formally declared war since 1942. Yet American presidents still order troops into battle while the public and its representatives cheer, carp, and, above all, watch.
Outlawing war has also given powerful states a paradoxical new rationale for waging war: enforcing international law. This danger was detected at the time by Carl Schmitt, the right-wing jurist and Nazi who submitted liberal internationalism to relentless criticism in the 1920s and ’30s. Where liberals hoped to subordinate states to rules and war to peace, Schmitt retorted that the devices needed to do this would inevitably be wielded as weapons by the powerful. The Paris Peace Pact, he argued, “does not outlaw war, but sanctions it,” because the signatories put forward a raft of exceptions (on grounds like self-defense and vital interest) that would allow them to wage war when they wanted and yet attack their enemies for violating this solemn pledge. Frank Kellogg went so far as to exempt any action that the United States took under the Monroe Doctrine, through which it claimed the right to police the Western Hemisphere.