Rejecting Lex Specialist, Affirming Systemic Integration: The ICJ’s Advisory Opinion in Obligations of States in Respect of Climate Change

In its landmark advisory opinion on the Obligations of States in Respect of Climate Change, the International Court of Justice opined that States have obligations under a wide range of treaties, and customary international law, to, among other things, ensure the protection of the climate system from anthropogenic greenhouse gas emissions, and to prevent significant harm thereof. While its findings will be studied on many issues for decades to come, the present commentary focuses on an underlying matter of methodology. As a Court with general subject- matter jurisdiction, the Court was entrusted with the request for an advisory opinion to opine on the implications of a variety of international legal norms. It was argued by some participants that the climate change treaty regime constituted lex specialis, i.e., a body of special rules which precluded the applicability of other rules of international law that may, otherwise, have been relevant as regards the conduct of States with respect to climate change. The Court, however, rejected this argument; not only that, the Court affirmed the necessity to interpret certain norms in question whilst taking account of other relevant rules of international law, i.e., it signalled support towards the systemic integration principle in the climate change context. This commentary studies the approach of the Court on both a general and granular level, seeking to examine the key insights and noteworthy omissions in the reasoning of the Court on the interrelationship between a variety of international legal norms. It will be seen that the Court’s approach reflects a balance of harmonisation, respecting the consent of States not to be bound by certain rules, and a pragmatism in international climate change governance.