My research focuses on the intersection of international relations and international law. Specifically, I seek to understand the different ways international law constrains the conduct of states. There is a growing tendency in the literature to argue that international law shapes the behavior of states via a logic of appropriateness rather than the logic of consequences stressed by realists and neoliberal institutionalism. By contrast, I understand the core evolution in law to be a more nuanced understanding of reciprocity. Building on Robert Keohane’s distinction between specific and diffuse reciprocity, I distinguish between two types of specific reciprocity: legal and strategic. While legal reciprocity involves the reciprocal commitments that states build into the wording of international law, strategic reciprocity can be used as a policy device regardless of the law. This understanding of reciprocity gives my research an appreciation of domestic debates regarding international obligations that are missed by other logic of consequences approaches.

I explore one aspect of this theme in my book The Persistence of Reciprocity in International Humanitarian Law (Cambridge University Press, 2019). Here, I consider the ability of international humanitarian law to constrain state behavior. This project involved a study of both the history of the law itself and the diplomatic negotiations surrounding the updating of the Geneva Conventions in 1949 and the creation of Additional Protocols I and II in 1977. My more nuanced theory of reciprocity demonstrates that, with respect to applying Geneva Convention III obligations, states have always understood these obligations as contingent on the reciprocal compliance of their opponents. I then applied this finding to the Johnson administration’s decision to apply Geneva Convention III to the War in Vietnam and the Bush administration’s decision to deny its application to the War on Terror. Contrary to critics who dismissed the Bush administration’s decision as a rejection of its international legal obligations, my approach demonstrates a continuation of a reciprocity-based understanding of such laws.