Bridging Comparative and International Law:Amicus CuriaeParticipation as a Vertical Legal Transplant

Legal transplants scholarship has thoroughly examined the transnational diffusion of legal institutions. Although Article 38 of the Statute of the International Court of Justice acknowledges that international law draws upon domestic legal systems, the exchange of legal institutions between states and international law has yet to receive similar treatment. This article highlights the process of vertical diffusion – that is, the borrowing of legal institutions between the nation-state and international law. Vertical diffusion takes place in two forms: downward and upward diffusion. Scholarship on the internalization and vernacularization of international law has highlighted the process of downward diffusion. This article offers a theory of internationalization of law and the emergence of internationalized legal transplants. It draws on a study of the internationalization of the amicus curiae participation procedure from the United Kingdom to the European Court of Human Rights. Three main conditions must be present for internationalization: the institution’s structural transformation that results in a law-making opportunity, norm entrepreneurs, and access to the decision-making body. The study of internationalized legal transplants is important to have a more fine-grained perspective on the making of international law. The evidence of the diffusion of legal institutions between domestic law and international law also creates a bridge between international law and comparative law scholarship.