Reasoning Up: Environmental Rights as Customary International Law

Most inquiries into the existence of customary law either reason inductively to derive custom from the course of state-to-state interactions, or deductively from multilateral instruments. Either way, this analysis is top-down, looking at whether international conduct has crystallized into customary norms. This chapter takes a different, bottom-up approach, looking at the obligations states have imposed on themselves through their own domestic laws. Focusing on the near-universal adoption of environmental impact assessment laws, it argues that some key components of a human rights-based approach to environmental protection have hardened into customary international law. The chapter also shows how similar inquiries could be conducted for other elements of the right, including in particular procedural duties relating to public participation and access to remedies for environmental harm, which are reflected in many domestic and regional environmental laws.