The chapter deals with well-established doctrine dealing with business regulation, including rate regulation, and intergovernmental tax immunity and other issues associated with the structure of government. The cases discussed show a sometimes simple, sometimes complex interplay between the stated doctrine and economic considerations, including concerns about the extent to which regulation nominally in the public interest actually served the narrow interests of specific economic actors. The chapter also examines the novel doctrine of propsective overruling, where formalism sharply conflicted with practicality.