Conrado M. Cornelius delivered a presentation titled “Conceptualizing International Climate Obligations Erga Omnes” at the 3^rd Edition of the Lisbon Climate Conference with the theme “Paris Climate Agreement.” The Conference was held in Lisbon, Portugal, on 24 October 2025; hosted by the Católica Faculdade de Direito Lisboa.

ABSTRACT: 

Conceptualizing International Climate Obligations Erga Omnes

• Certain climate obligations under international law are erga omnes. Drawing upon the jurisprudence of the International Court of Justice (ICJ), this dissertation examines the defining characteristics of erga omnes obligations, their emergence and evolution in international law, and their distinctiveness from bilateral obligations and jus cogens norms, and contextualizes them in the context of climate change. This dissertation analyzes how climate obligations, particularly those arising from treaties, customary international law, and unilateral declarations, can be classified as erga omnes or erga omnes partes.
• This research addresses the complexities of enforcing erga omnes obligations in international law and the ambiguities surrounding the legal standing of non-injured third-party States in bringing erga omnes claims, particularly those stemming from customary international law. The recognition of some international obligations as erga omnes does not necessarily follow, as a corollary, that any State may seize the jurisdiction of international courts and tribunals, particularly the ICJ, to seek the enforcement of those obligations by way of actio popularis. As a solution to the problem of enforcing erga omnes obligations in international law, this dissertation argues that while the notion of actio popularis enforcement of erga omnes obligations may be controversial as a matter of general public international law, there is a possibility to justify the granting of actio popularis standing as a general principle of law, aided by a systemic integration approach, at least in the international environmental-climate law regime. However, despite its prospects, the enforcement of these international climate obligations erga omnes may be limited only through mechanisms of special agreement, forum prorogatum, and/or optional clause.

The actio popularis enforcement of these international climate obligations erga omnes also has the potential of shifting the paradigm for future (international) climate litigation from the idea of corrective justice to distributive justice. By granting prospective litigant States with actio popularis standing, the structure of future international climate litigation will no longer be confined to the bilateralist logic of State responsibility between an injured State and the State committing the wrongful act guided by corrective justice, but shifting to an international responsibility for non-bilateral international obligations guided by the communitarian logic of distributive justice.