As more and more countries around the globe are amending their constitutions to recognises environmental rights and duties relating to air, water, the use of natural resources, sustainability, climate change, and more, courts are increasingly engaging with these provisions and developing a common constitutional law of environmental rights. This article examines this growing jurisprudence and surveys the central axes around which debates about environmental constitutionalism revolve. First, we examine whether environmental rights are more suitably advanced at the international level or at the national level of constitutional law, as is increasingly the case; the former offers two alternatives—protecting the environment for its own sake or protecting it as a human right, whereas constitutionalism tends to integrate the two approaches. Concluding that international protection presents problems of articulation and enforcement, we examine the arguments for protection of environmental rights at the level of national constitutionalism. Lastly, we argue that engaging in comparative constitutionalism is a necessary component of understanding the envisioned reach and inherent limitations of environmental constitutionalism.