nternational Investment Law (IIL) is a highly specialized discipline, but does not exist in a legal vacuum. It is created, applied and interpreted in a context of general, legal concepts, including the law of treaties, State responsibility, diplomatic protection and State immunity. The contributions to this volume assess the interrelation between IIL and these areas of general international law. They provide evidence of IIL ‘opting out’ of the general framework, but also of integration and cross-fertilisation. Taken together, they illustrate the varied interactions between general international law and one of its most dynamic sub-areas.