This book examines the systematic constraints on US law enforcement agencies' efforts to regulate business behaviour. It looks specifically at the postwar development of laws regulating water pollution and at the Environmental Protection Agency's efforts to enforce them. The discussion traces the factors leading to legal change and analyses the ways in which the impacts of environmental laws vary from their stated purposes and goals, even under relatively favourable conditions for their enforcement. It shows how legal processes and social relations mutually constrain and shape one another as the state struggles to manage often contradictory responsibilities, in this case to encourage both economic growth and environmental welfare.