RECENT INVESTMENT TRIBUNALS HAVE ADOPTED A VARIETY OF transparency standards in investor-state arbitral practice. The requirements for openness in investment dispute settlement have  included: considering amicus briefs, publishing memoranda, awards, and witness statements and allowing for access to parties’ pleadings, transcripts and public hearings either digitally or physically. This practice leads actors to reconsider their positions on transparency as set out in international investment agreements (IIAs), annexes to arbitral rules or memoranda of state. Under pressure to keep further arbitration proceedings open to the public, some actors are now eager to create a new multilateral standard of transparency. The United Nations Commission on International Trade Law (UNCITRAL) Working Group II (WG) has proposed a standard (Standard) which, to some extent, may find consensus within the mandate of the WG and the arbitral community. However, it is uncertain how such a standard will interact with existing IIAs and contractual obligations of host-states and investors.

This paper examines the likely effects of applying the proposed Standard in investor-state disputes arising from existing IIAs and investigates how the proposed Standard should be implemented in order to overcome potential obstacles. It argues that a multilateral memorandum of understanding, including commitments from both investors and homeand host-states, is necessary to ensure participation from the maximum number of investors and states.