The notion that arbitrators owe duties to the parties in investor-state disputes is familiar. This article explores less-trodden terrain. It argues that, notwithstanding the party-centric norms of arbitration, investment arbitrators also owe duties to non-parties. It begins by establishing a beachhead – a clear example of a duty to a non-party, as a proof of concept – before moving into rougher territory. The article catalogs and surveys various duties owed to non-parties, discussing the nature of these duties and how they are enforced. Finally, the article shows that recognizing duties to non-parties both informs a proper understanding of the investment arbitration system and may help improve that system
