How does the transnational legal process, based on international human rights law, affect domestic constitutional law? This chapter analyses how domestic constitutional regimes interact with the Inter-American Human Rights System. It argues that structural transformations in international law together with broader legal interaction have allowed new players to behave as constitutional actors articulating political claims in the language of fundamental rights. This process inaugurates possibilities of reshaping constitutional law, allowing civil society actors to bypass domestic institutional obstacles to human rights enforcement. The parallel development of the Inter-American Human Rights System as an independent regime with a plurality of domestic answers to its normative growth leads to a unique path of development, adding an interesting set of models of transversal human rights governance to the broader field of ‘global governance’.