Particularly in the context of public law, comparative law scholarship typically involves a comparison of legal norms, principles, actors, or legal institutions in different state jurisdictions or across legal traditions. The rise and increasing prevalence of transnational regulators – particularly transnational non-state regulators, but also hybrid and intergovernmental varieties – challenges this methodological default. It invites us to consider the nature of regulation across different legal regimes, some of which might be overlapping, and which, in their claims to authority, might be complementary or conflictual. Acknowledging the presence of transnational regulators within a plurality of legal orders raises questions about how state-centric regulatory institutions at the sub-national, national, regional, or international levels differ from hybrid (state/non-state) and predominantly non-state regimes, whether in terms of their functions (e.g., in terms of standard-setting, enforcement, and dispute resolution) or in terms of their relative claims to authority and political legitimacy. This chapter shows how transnational law poses a conceptual and methodological challenge for comparative lawyers, yet one that reinforces recent innovations in the comparative law field, reflected in this Handbook, that extend comparative law beyond functional comparisons of rules, legal systems, or legal traditions.