(2026) 7 TWAIL Review xx–xx
ISSN 2563-6693
Published under a Creative Commons licence. 

This article examines how the rules governing amicus curiae submissions from Non-Disputing Parties in Investor-State ICSID arbitration can operate to silence Indigenous groups and other third parties with a direct interest. It interrogates how the nexus that Indigenous groups have with investment disputes is more akin to that of an intervener than an amicus. It critiques the bounded conception of international investment law adopted by certain Tribunals demonstrating an intolerance which makes the law unable to accommodate a plurality of voices, by denying that Indigenous law and rights can form part of the applicable law, and by finding Indigenous groups have too much of an interest to be amici. It argues that the 2022 ICSID Rules were a missed opportunity to create a new category of Third-Party Intervener.