Against the background of climate change, the Energy Charter Treaty and the law and policy of the European Union are no longer fully aligned with each other: in the case of a conflict in the area of investment regulation, what norms should apply? Within the framework of the ongoing reform of the international investment system, notably, investor-State dispute settlement, and of the modernisation of the Energy Charter Treaty, Ottavio Quirico explores how to approach regulatory conflicts and re-harmonise the Energy Charter Treaty with the law of the European Union.