 First, proportionality in international law is markedly different from the version of the principle that first-order moral theory supports. At law, an act of war is proportionate insofar as the harm to civilians is not excessive in relation to the concrete and direct military advantage realized thereby. As noted above, in first-order moral terms, this is unintelligible. But there might be a better institutional argument for this neutral conception of proportionality. Proportionality calculations involve many substantive value judgements—for example, about the significance of moral status, intentions, risk, vulnerability, defencelessness, and so on. These are all highly controversial topics. Reasonable disagreement abounds. Many liberals think that coercive laws should be justified in terms that others can reasonably accept, rather than depending on controversial elements of one’s overarching moral theory (Rawls 1996: 217). The law of armed conflict is coercive; violation constitutes a war crime, for which one can be punished. Of course, a more complex law would not be justiciable, but we also have principled grounds for not basing international law on controversial contemporary disputes in just war theory. Perhaps the current standard can be endorsed from within a wider range of overarching moral theories than could anything closer to the truth.