Methodological Innovations in the ICJ's Climate Advisory Opinion: A Systemic and Science-Based Approach to International Law

While the International Court of Justice (ICJ) advisory opinion on Obligations of States in Respect of Climate Change has already been widely discussed, little attention has yet been paid to the method followed by the Court, which is the subject of this commentary. Indeed, the Court followed a methodological approach advancing a progressive interpretation of international climate law. The ICJ made choices that enabled it to issue a bold opinion. First, the Court drew on climate science to establish the legitimacy and authority of its opinion. Second, it mobilized a wide range of international law sources, very clearly and firmly rooting the opinion in a systemic vision of international law, which allowed it to interpret the various applicable norms in a synergistic manner.