Because of the transboundary nature of most environmental problems, environmental policy often lies at the intersection of domestic and international forces. Yet, because domestic and international issues are usually examined with different sets of theories and models, we tend to explain the policy process and outcome by emphasizing only one arena. Analysis of domestic policy is often dominated by process models, whereas scholars of international relations tend to apply rational models to explain state behavior. We apply Kingdon's 'policy windows' model of agenda setting and Brams's dynamic game theory framework so the development of acid-rain legislation enacted by the USA in the Clean Air Act of 1990. We compare the explanations of these theories with the work of other analysts, as well as with perceptions of policymakers by using data from interviews of policymaking elites in Canadian and US government, industry, and interest groups. It is demonstrated that process models and models of strategic interaction can complement each other, providing improved explanations of policy outcomes.