This chapter examines the most significant limitations on the power of private parties to choose a governing law, identifying a variety of approaches in different legal systems. Three such types of restrictions are analysed. The first is based on the subject matter of the dispute or the characteristics of the parties, such as limitations on choice of law for consumer and employment contracts. To protect weaker parties a choice of law may be excluded entirely, limited in terms of possible options, open to review, or subject to limited effectiveness. A second type of restriction is based on whether and to what extent the parties are able to choose foreign law in a situation purely connected to a single legal system. A third type of restriction arises from the doctrines of mandatory rules and public policy. Mandatory rules are typically forum statutes which override the application of foreign law, including where that law has been chosen by the parties. Protecting their application may also be considered to require restricting party choice of forum. Public policy operates as a final residual safety-net where the content of foreign law, including a law chosen by the parties, is contrary to forum values.