This article presents a legal perspective on regulatory institutions, procedures and processes. Analysis of legal instruments examines justifications for regulatory interventions, and considers the inadequacies of private law remedies to instances of market failure (such as monopolies, inadequate or asymmetric information, externalities and co–ordination problems). A distinction is drawn between social and economic regulation: the former deals with such matters as health and safety, and environmental and consumer protection; and the latter is needed where there is insufficient competition. Instruments of social regulation include prior approval, mandatory standards and information disclosure. A range of instruments of economic regulation is also assessed, including competition law, public ownership, price and quality regulation, and competitive public franchising. Analysis of regulatory processes focuses on regulatory rule–making, delegated regulation and self–regulation. Particular weight is given to different forms of accountability—financial, procedural and substantive—which draws attention to the significance of the public interest dimension of regulatory systems.