International Environmental Law and Global Agreements

International environmental law is the branch of public international law concerned with preventing, controlling, and remedying environmental harm that crosses national boundaries or affects the global commons. This chapter examines how the international community constructs, operates, and seeks to enforce the treaty-based regime governing climate change, ozone depletion, marine biodiversity, hazardous chemicals, transboundary air and water pollution, and other shared environmental challenges. The body of international environmental agreements has expanded from a small number of bilateral arrangements to more than 700 multilateral environmental agreements and 1,000 bilateral agreements documented in the literature, covering pollutants, species protection, habitats, and the global commons. The chapter reviews the foundational principles underpinning this architecture, including the no-harm rule, the precautionary principle, common but differentiated responsibilities and respective capabilities, and intergenerational equity, and evaluates their use in treaty design. The Montreal Protocol, the Paris Agreement, and the Biodiversity Beyond National Jurisdiction Agreement are examined as contrasting governance cases. Persistent weaknesses are also considered, including the compliance - enforcement gap, fragmentation among overlapping regimes, and the North - South divide in obligations, finance, and technological capacity. The chapter concludes that international environmental law has developed a dense and increasingly coordinated institutional architecture, but that the central governance challenge remains converting formal commitments into measurable environmental outcomes.