Book excerpt: General Principles of Law in Investment Arbitration surveys the function of general principles in the field of international investment law, particularly in investment arbitration. The authors’ analysis provides a representative case study of how this informal source operates alongside and in the absence of other sources of applicable law. The contributions are divided into two parts, devoted respectively to substantive principles and procedural ones. The principles discussed in the book are selected for their currency in the practice, their contested nature and their relevance.