Measuring Without a Ruler: Assessing Compliance with Calculative International Norms

Measuring compliance with international norms is usually taken to be a relatively straightforward exercise. To determine whether a state is compliant, scholars typically measure the level of conformity between their behavior and "the letter of the law." IR theorists often disagree over whether compliance tells us anything meaningful about the causal effects of international norms, but most believe that it can at least be measured. We argue that, for certain norms and laws, this claim is too optimistic. We draw on recent insights from moral philosophy and moral psychology to distinguish between two types of international norms: (1) proscriptive norms that govern state practices by providing fairly specific rules of appropriateness for how states or other actors are expected to behave and (2) calculative norms, which do not stipulate any particular rules of appropriateness, but rather require that states take efforts to maximize or minimize a specific value. The laws of war, for example, hold that states cannot target civilians (proscriptive), but they do allow for tactics that generate collateral damage, as long as it is minimized (calculative). Because assessments of conformity between state practices and calculative norms require evaluation of intentions-which can be difficult at best to obtain, particularly in instances where actors have incentives to mislead or dissemble-measuring compliance by assessing behavior and its consequences can be very misleading and lead to false negatives. Using US bombing policy in Vietnam as an illustrative case, we show that failing to observe the differences between norm types can lead to confusion when evaluating the effects of international law.