This article starts by discussing a number of public interest explanations for regulating the markets of legal services: information asymmetries, negative externalities and public goods. Since professional associations of lawyers meet the requirements for acting as effective lobbyists, the article subsequently investigates private interest explanations. Empirical work to test alternative theories of professional regulation so far remains limited and the results are ambiguous. Even if empirical studies are able to show that there exists a correlation between levels of professional regulation and profits earned, firm policy conclusions cannot be drawn as long as quality is not adequately assessed. After an overview of the theoretical and empirical literature, the article suggests a number of best practices for policy making. The two most important guidelines seem to be the following. Regulation should not be profession-focused but targeted at market failures in particular segments of the legal services markets. Changes of the regulatory infrastructure that create scope for competitive self-regulation may be the best way for coping with market failures and at the same time reducing the scope for rent-seeking.