Strong procedural elements are indispensable for international environmental law’s capacity to serve community interests. Procedural obligations can strengthen the rule concerning the prevention of environmental harm and flesh out its due diligence standard. Procedural obligations can also serve useful purposes when states, or judges, are reluctant to entertain substantive arguments, or find it difficult to establish that environmental harm has been caused. Violations of procedural obligations are more easily established and states can sometimes be prompted to correct harmful conduct or to take more effective preventive measures. Unfortunately, the operation of procedural rules is constrained by the dearth of practice and the continued struggle to define the substance of community obligations and the legal effects of erga omnes norms. Treaty-based approaches have proven better suited to accommodating community concerns, perhaps because they place such strong emphasis on procedural elements and employ increasingly diverse formal lawmaking and informal standard-setting approaches.