The Proliferation of Joint Interpretation Clauses in New International Investment Agreements: A Mixed Blessing?

Joint interpretation clauses (JICs) are among the most controversial control mechanisms on the interpretative powers of tribunals brought by the current wave of reform of the investor–State dispute settlement system (ISDS). Literally proliferating in the new generation of international investment agreements (IIAs), these clauses give contracting States the power to issue joint interpretations (JIs) that are expressly recognized as binding upon dispute settlement bodies and may even be issued in relation to matters pending before such bodies. This article discusses several issues raised by the ‘authentic interpretation’ enhanced by JICs. In the first part, JICs are assessed against the background of the general rule on treaty interpretation, including, in particular, subsequent agreements under article 31(3)(a) of the 1969 Vienna Convention on the Law of Treaties. The second part of the article addresses the tensions between judicial bodies and treaty parties sharing the interpretative authority over IIAs and investigates whether there are any limitations on the interpretative powers of States under JICs. The third part is devoted to the impact of JIs on the proper conduct of investment arbitration proceedings, considering the participation of private actors (the investors) in the proceedings and the ‘dual role’ of States (as treaty parties and respondents) in this field. The concluding part of the article speculates whether a greater institutionalization of the international investment regime is likely to prompt more frequent forms of judicial reactions against ‘ill-perceived’ JIs and fuel the tension between States and dispute settlement bodies.