Climate Constitutionalisation in Europe—After KlimaSeniorinnen and the ICJ’s Advisory Opinion

Several European courts have vested mitigation obligations with a hierarchically higher legal rank than ordinary state action. They construe these obligations from human rights in combination with international commitments and climate science. This phenomenon is here called ‘climate constitutionalisation’. In addition, we see an increasing escalation of climate cases to the European Court of Human Rights (ECtHR) and we now have the advisory opinion of the International Court of Justice (ICJ). Climate constitutionalisation in Europe is an incremental process of replication and reiteration. It can only be understood by studying the developing body of national case law in the context European and international law. Studying general emission reduction cases against states in Europe, this paper traces how non-enforceable legal norms, political commitments, and climate science are used to interpret binding and enforceable human rights norms. It reflects on the present and future consequences of the ECtHR’s decision in KlimaSeniorinnen and ICJ’s Advisory Opinion on climate obligations. The paper argues that Europe’s multilayered legal and judicial landscape strengthens climate constitutionalisation and herewith deepens the fault line between the judiciary and the elected institutions. Europe’s openness towards international law facilitates this process. The paper then offers tentative normative justifications for this process.