Private Law Theory

ABSTRACT
Private international law – or conflict of laws, as it is commonly referred to in the United States – deals with the co-existence of different legal systems and determines which state’s law applies (should apply) in cross-border cases. It is traditionally regarded as a rather apolitical and value-neutral field of law. In the 20th century, however, private international law has undergone a ‘regulatory turn’. The chapter explores the nature, origins and implications of this transformation with a particular focus on European private international law. It argues that private international law today not only coordinates legal systems but actively contributes to the pursuit of regulatory goals. Specifically, it shows that private international law advances regulatory goals in two ways: First, in an indirect fashion through the extension of the spatial reach of substantive rules and through the protection of substantive rules from displacement. And, second, in a direct fashion through the integration of regulatory goals into its very own choice-of-law rules. At the same time, the chapter critically examines the role of party autonomy and argues that, while it supports broader policy objectives such as the functioning of the internal market, it should not be understood as a regulatory instrument in a strict sense, but rather as a form of legal infrastructure. Building on these insights, the chapter highlights the increasing importance of private international law for the effectiveness of national and European regulation in cross-border contexts. It concludes that many contemporary challenges – such as the regulation of digital markets, the fight against climate change and the pursuit of sustainability – can only be effectively addressed if the regulatory function of private international law is fully recognised and appropriately developed.

Ruhl, Giesela, Regulating Contracts across Borders: The Role of Private International Law (May 16, 2026) in Yesim Atamer and Alexander Hellgardt (eds), Oxford Handbook on Regulatory Contract Law, Oxford University Press, forthcoming.