Abstract This Article examines international law from the perspective of compliance Using insights from international relations theory, the article adopts a theory in which compliance comes about in a model of rational, self-interested states. Specifically, states are concerned about both reputational and direc t sanctions tor their conduct The model allows us to consider international law in a new strikingly, one is forced to reconsider two of the most fundamental doctrinal points in the field -the definitions of customary international law( CIL) and of international law itself. A reputational model of compliance makes it clear that Cil affects the behavio of a state because other states believe that the first state has a commitment that it must honor. A failure to honor that commitment hurts a state's reputation because it signals that it is prepared to breach its obligations. This implies a definition that turns on the existence of an obligation in the eyes of other states rather than the conventional requirements of state practice and a sense of legal obligation felt by the breaching state Classical definitions of international law look to two primary sources of law treaties and CIL. A reputational theory, however, would label as international law any commitment that materially alters state incentives. This includes agreements that fall hort of the traditional definition, including what is often referred to as "soft law. "The Article points out that there is no way to categorize treaties and Cil as " law"without also including soft law. Agreements such as ministerial accords or memoranda of understanding represent commitments by a state which, if breached, will have a reputational impact. For this reason, these soft law agreements should be included in the definition of international law The Article also calls for a refocusing of international law scholarship. Because international law works through reputational and direct sanctions, we must recogni that these sanctions have limited force. As a result, international law is more likely to have an impact on events when the stakes are relatively modest. The implication is that many of the topics that receive the most attention in international law- the laws of war territorial limits, arms agreements, and so on - are unlikely to be affected by international law. On the other hand, issues such as international economic matters, environmental issues, and so on, can more easily be affected by international law. This suggests that the international law academy should focus greater attention on the latter subjects and less on th e formerAbstract This Article examines international law from the perspective of compliance. Using insights from international relations theory, the Article adopts a theory in which compliance comes about in a model of rational, self-interested states. Specifically, states are concerned about both reputational and direct sanctions for their conduct. The model allows us to consider international law in a new light. Most strikingly, one is forced to reconsider two of the most fundamental doctrinal points in the field – the definitions of customary international law (CIL) and of international law itself. A reputational model of compliance makes it clear that CIL affects the behavior of a state because other states believe that the first state has a commitment that it must honor. A failure to honor that commitment hurts a state’s reputation because it signals that it is prepared to breach its obligations. This implies a definition that turns on the existence of an obligation in the eyes of other states rather than the conventional requirements of state practice and a sense of legal obligation felt by the breaching state. Classical definitions of international law look to two primary sources of law – treaties and CIL. A reputational theory, however, would label as international law any commitment that materially alters state incentives. This includes agreements that fall short of the traditional definition, including what is often referred to as “soft law.” The Article points out that there is no way to categorize treaties and CIL as “law” without also including soft law. Agreements such as ministerial accords or memoranda of understanding represent commitments by a state which, if breached, will have a reputational impact. For this reason, these soft law agreements should be included in the definition of international law. The Article also calls for a refocusing of international law scholarship. Because international law works through reputational and direct sanctions, we must recognize that these sanctions have limited force. As a result, international law is more likely to have an impact on events when the stakes are relatively modest. The implication is that many of the topics that receive the most attention in international law – the laws of war, territorial limits, arms agreements, and so on – are unlikely to be affected by international law. On the other hand, issues such as international economic matters, environmental issues, and so on, can more easily be affected by international law. This suggests that the international law academy should focus greater attention on the latter subjects and less on the former