The study of the
uneasy interplay between investor-state dispute settlement (ISDS) and
sustainable development has already caused a great deal of ink to flow. While
there are some separate attempts to align international investment agreements
(IIAs) with sustainable development goals, most IIAs cannot accommodate such
objectives within their traditional frameworks. These tensions are especially
evident when an investment tribunal is invited to decide on a dispute that ultimately
produces long-term effects on societies. Amicus curiae and other forms of
third-party participation can enhance sustainable development standards within
international investment law, constituting one of the crucial procedural
pillars between these two competing regimes. This article scrutinizes various
forms of third-party participation in defending sustainable development
standards in the context of existing transparency and accountability safeguards
in investment arbitration. It explores the general legal standards and
developments in judicial practice, the critical modifications of investment
treaties and arbitration rules and assesses their impact on revitalizing
third-party participation, primarily through amicus curiae briefs, to advance
compliance with sustainable development standards.