At first glance, one may think of international investment law as a response to custom (or lack thereof), instead of a field of its application. However, in fact, the opposite is the case. The interpretation and application of customary rules and principles are the bread and butter of international investment law and arbitration. With a diverse range of expert contributors, this collection traces how customary international law is practised in international investment law. It considers how custom should be interpreted and how its rules and principles should be understood and applied by investor-state arbitral tribunals. Raising and addressing vital questions surrounding custom and international law, this collection is a necessary contribution to the scholarship of the theory and history of customary international law and international investment law. This title is also available as Open Access on Cambridge Core.

Although customary international law (CIL) has been central to international law from its inception, it is often misunderstood. This edited volume remedies that problem by tracing the history of CIL and provides an in-depth study of its theory, practice, and interpretation. Its chapters tackle the big questions which surround this source of international law such as: what are the rules that regulate the functioning of CIL as a source of international law? Can CIL be interpreted? Where do lines between identification, interpretation, application, and modification of a rule of CIL lie? Using recent developments, this volume revisits old debates and resolves them by proffering new and innovative solutions. With detailed examples from international and national courts, it places CIL in a range of settings to explain, explore and reflect upon this developing and highly significant field. This title is also available as Open Access on Cambridge Core.

The law of treaties is in constant motion, understood not only as locomotion, but also as motion through time and as change. Thus, kinesis and stasis, two sides of the same concept of 'motion', are the central themes of Treaties in Motion. The concept of motion adopted in this book is based on the philosophy of Aristotle. He identified six types of motion: creation (genesis), increase (auxesis), diminution (meiosis), alteration (alloiosis), destruction (phthora), and change of place (kata topon metabole), which has been amended by the authors to change in space-time (kata topon kai chronon metavole) to reflect our modern scientific understanding of time as a dimension through which motion and change occurs. Each chapter's analysis proceeds by focusing on a specific area of a treaty's 'life-cycle', where each type of motion shines through and is described through three different frames of reference: treaties, the Vienna Convention of the Law of Treaties, and customary law.

In Article 31(3)(c) VCLT and the Principle of Systemic Integration: Normative Shadows in Plato's Cave the author tackles a provision on treaty interpretation that has risen in prominence, Article 31(3)(c) VCLT. This article, which enshrines the principle of systemic integration, and its exact scope has become and continues to be a hotly debated subject in academic and judicial circles. Through an examination of both its written and unwritten elements, the author argues that the 'proximity criterion' is the optimal way of understanding and utilizing this provision, that conflict resolution principles may be of use within Article 31(3)(c) and finally, that the principle of systemic integration is indispensable not only for interpreting treaty provisions but customary international law as well.