Chapter 3 delves into the functions and foundations of international environmental law. International environmental law is an institution based on the deliberate redundancy of parallel and overlapping networks that contribute to its resilience and to the maintenance of the minimum public order. We analyze the foundational purposes of international environmental law: the quest for equity and the pursuit of effectiveness. We underline that addressing matters of distributive equity successfully is the sine qua non condition for the effective protection of environmental commons. The tragedy of the commons rationale that precipitated the enclosure of common pool resources in national systems is also driving the enclosure of global common resources. This chapter analyzes the specifics of this enclosure, as it has been unfolding in fisheries, marine genetic resources, germplasm resources and related knowledge, deep-seabed resources, freshwater resources, air, seas, chemicals, wastes, and space. The nature of inclusionary and exclusionary enclosures and how these types of enclosure affect perceptions of distributive equity are critically examined. Finally, international environmental regimes are evaluated based on the effectiveness of the enclosure they have commanded and the perceptions of equity held by the stakeholders and participants in the regimes.