State-society differentiation and political centralization interact to influence the amount, focus, and effect of legal activity. Using case studies of antinuclear power litigation in the 1970s in the United States, West Germany, France, and Sweden, this article develops a general theory of political systems and legal activity. While the United States, West Germany, and France all had considerable amounts of antinuclear litigation, in France and Germany such litigation was directed almost exclusively at the state. In the United States, the targets of antinuclear litigation were much more diffuse. Centralized Sweden with its corporatist political system had significantly less antinuclear legal activity than the other three countries, which were roughly comparable. Germany was the only country in which the state took an active role in shaping the content of legal cases, and it was the only country where litigation became a critical factor in modifying national policy. Through these case studies, this article explores how contextual factors such as the political frames of nation-states, which exist apart from individual litigiousness and even apart from legal systems themselves may create particular cross-cultural variations in patterns of legal activity.