Amici curiae are individuals or organisations who do not have the right to participate in the dispute as parties but want to intervene because the outcome of the proceedings may affect their interests. The participation of amici in investor-state arbitration has been justified as a useful tool...

Amicus curiae is a developing feature of modern international investment arbitration. This chapter starts by describing how investment arbitration shifted from a confidentiality-based practice to a model that is more open to the participation of civil society. It then proceeds to discuss the...