This contribution examines the use of third-party submissions, such as
amicus curiae submissions, in investment treaty arbitrations. The author shows
that a surprisingly low number of amicus curiae submissions have been submitted
so far and consequently have not resulted in any discernible impact on the
jurisprudence of arbitral tribunals. At the same time, interventions by
non-disputing treaty parties appear to be more effective. The author also
discusses the ambiguous nature of amicus curiae submissions made by the
European Commission, which – it is argued – are actually more akin to
non-disputing party interventions. The author concludes that amicus curiae
submissions could be better crafted and used more often to achieve greater impact.
In addition, they could also be targeted more often against States and their
failures in implementing their international environmental obligations.