South Centre Report, September 2026

Beyond Amicus Curiae: Rethinking the Role of Third-Party Participation in Investment Arbitration and Environmental Governance

By Paulina Kuehme, Lakshmi Swathi Ganti, Brian Kelly Nyaga, Mattia Semenza

Supervisor: Prof. Elena Cima

Prepared for the South Centre as part of the Geneva Graduate Institute’s LL.M. Legal Clinic Programme, International Environmental Law and Governance Stream

This document examines third-party participation in Investor-State Dispute Settlement (ISDS), with a particular emphasis on environmental considerations. It investigates how to ensure procedural fairness and enable meaningful involvement of affected communities in cases concerning environmental protection. The study assesses the scope and challenges of such participation, including the ability to present evidence and legal arguments related to environmental impacts. It also explores the potential role of third-party involvement in shaping counterclaims against investors for environmental damage, and its possible influence in mitigating compensation by introducing arguments and evidence related to environmental costs. Through this analysis, the project aims to support a more balanced and sustainable ISDS framework – one that protects both investors and the environment – while fostering community empowerment and strengthening accountability for environmental harm.

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Beyond Amicus Curiae: Rethinking the Role of Third-Party Participation in Investment Arbitration and Environmental Governance