The Emergence of the Concept of 'General Principle of International Law' in Investment Arbitration Case Law

This article examines the concept of 'general principle of international law' and the way it has so far been used by tribunals in investment cases. It will first outline the nature and meaning of these principles emerging on the international plane and distingue them from other general principles grounded in States' domestic laws. The empirical analysis of four general principles (burden of proof, estoppel, res judicata and abuse of rights) shows that many tribunals have explicitly recognized them as general principles of international law. The reasoning of other tribunals, the expressions they have used and the international law material they have referred to strongly suggest that they have also come to the same conclusion. Finally, this article considers the reasons why this concept is important to the further development of investment arbitration.