Why do states pursue different policies, and experience varying outcomes, in response to international agreements? I use an approach that focuses on the domestic political economy of states to examine the Kimberley Process, an international agreement implemented in 2003 to certify the world's diamond trade. Since the Kimberley Process is often indecisive, it is an interesting puzzle why states, even those that often ignore international agreements, will use scarce resources to raise their level of compliance with the Kimberley Process. In this research I conduct comparative case studies of four diamond wealthy countries in sub-Saharan Africa: Angola, Namibia, Sierra Leone and Zimbabwe. These cases provide a large variation in compliance and cooperation with the Kimberley Process, due to the extent that diamond dependency constrains the ability of state actors to implement their preferences surrounding policy, the preferences of private actors, and the relative amount of power within and between these groups. This research shows that cooperation and compliance with international agreements, especially those that have an economic element, can be better understood as a process that takes place domestically where different actors compete to get their policy preferences implemented and domestic economic changes lead to changes in policy implementation.