The relationship between international law and domestic law has long been a central topic of international law scholarship. For decades, debates raged between partisans of monist and dualist theories.1 More recently, scholars have turned away from theoretical conjectures to investigate the practical and policy implications of the rules and procedures that govern how states create international legal obligations and implement them domestically.2

It only takes a moment of reflection to realize that many of the questions raised by this scholarship lend themselves to empirical investigation. Is there a ‘‘democratic deficit’’ in international law-making? Is the traditional distinction between ‘‘monist’’ and ‘‘dualist’’ systems meaningful? Are some national legal systems generally more receptive to international law than others, and why? In addition to these more traditional questions, systematic empirical data on the status of international law in domestic systems allows us to explore the politics of international law. Depending on the question of interest, such rules can be regarded as an independent variables (e.g., does the fact that a legal system gives direct effect to treaties affect compliance with human rights obligations?) or as a dependent variable (e.g., how do various factors such as legal origins shape the regime for international law reception?)

Pierre-Hugues Verdier & Mila Versteeg, International Law in Domestic Legal Systems: An Empirical Perspective, 108 Proceedings of the American Society of International Law, 376–382 (2013).