The Peace of Westphalia released forces leading to the Industrial Revolution, ultimately freeing sovereign states to develop competing systems of economic development that had in common the uncontrolled exploitation of the environment. Over time, a law of humanity developed in response to the failings of a law of sovereign states in two main spheres: that of the dignity of the individual and that of matters of “common concern” that require a global, humanitarian response. Environmental issues have moved to the forefront of the latter, as can be demonstrated by an examination of terms used in international law to describe environmental matters, and have given rise to new forms of international and transnational cooperation. By being reminded that humanitarian issues of common concern were at the root of the Westphalian shift itself, we see that it is the radical form of sovereignty that developed in the 19th and 20th centuries that in fact proved inadequate. The key questions, therefore, are what the global environmental challenge teaches us about the potential for sovereignty to be “reclaimed” for humanity, and how and whence authoritative norms to modulate sovereignty will arise.