Lesley Wexler

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How do states manage disagreements about the application and interpretation of International Humanitarian Law (IHL)? As countries find themselves embroiled in conflicts across the globe and in need of allies' political, economic, and military support, this question is important from a practical standpoint as well as a theoretical one. This essay provides one set of answers by looking at the United States’ approach to potential IHL disputes with its allies. It opens with an exploration of the issues most likely to create divergence: the existence, typology, and scope of armed conflicts; the interaction between IHL and International Human Rights Law, as well as disagreements about permissible means and methods of warfare. I use modern examples from the war on terror to then illustrate how other states can manifest their preferences for the United States to follow or accommodate a distinct IHL approach. In particular, allies may significantly constrain the United States’ ability to maintain a divergent approach by: limiting interoperability; restricting territorial access; refusing to cooperate on intelligence matters; and denying access to individuals. This Essay concludes by dissecting the United States’ options for managing potential IHL divergence and identifying the costs and limitations of various strategies. In the war on terror, the United States sometimes uses secrecy and obfuscation; legal precommitments; and political or economic persuasion to get other states to accept its position on IHL. In other cases, the United States may abandon its IHL approach and harmonize out of deference to an ally. And lastly, the United States may, of course, continue to use its existing interpretations and maintain its preferred behavior without the support of specific allies. But even then, divergence may shape U.S. national security policy by encouraging it to find new partners for particular activities or forcing it to go it alone on activities and procurement for which it would prefer to have support.