Third-Party Participation in Investment Arbitration Proceedings

Abstract

This article examines the development of thirdparty participation in investment arbitration, particularly through amicus curiae submissions, as a significant manifestation of increased transparency in investor–State dispute settlement. It analyzes the legal foundations and codification of such participation in international procedural rules and investment agreements, highlighting UNCITRAL, ICSID, and U.S. and Canadian models. It also reviews arbitral practice through landmark cases such as Methanex, UPS, and Biwater Gauff. The article concludes that thirdparty participation has brought investment arbitration closer to judicial adjudication and strengthened consideration of the public interest, while raising challenges concerning confidentiality, party autonomy, and procedural rights.