As chapter 3 has shown, the ability of international institutions to monitor states' compliance varies. Perhaps more interesting is the fact that, even when international institutions provide compliance information, it is often not states that use the information to either reward or sanction other states. We are thus confronted with another puzzle: when international institutions do not seem to be enabling states to use carrots and sticks on each other at the international level, what drives states to comply with international commitments?

This chapter investigates domestic sources of compliance. As reviewed in chapter 2, the analytical foundation of cooperation theory and regime theory has an enduring impact on the contemporary study of compliance. To answer the realist challenge, scholars of international institutions have sought to demonstrate the direct effect of international institutions on states' behavior. As a result, these studies have not paid systematic attention to a critical piece of the compliance puzzle. That is, why do different countries participating in the same agreement achieve different levels of compliance? To answer such questions, we must bring domestic politics into the study of compliance and international institutions.

I argue that problems that resemble a PD at the international level may present governments with an entirely different strategic environment domestically. Within a country, some actors gain while others may lose if the government does not comply with an international agreement.