Lecture Summary: The lecture will consider the role of the conflict of laws before international courts and tribunals. Very rarely is the conflict of laws examined in the writings on public international law or is applied in the decisions of international courts and tribunals. And that is surprising given that disputes that become the subject of adjudication before investment courts and tribunals are necessarily cross-border in nature. And their cross-border character undoubtedly calls for the partitioning of legal issues among legal systems. The lecture will examine a number of inter-related issues: 1) which conflict of laws rules are to be used by international courts and tribunals in determining the rights and obligations at the municipal law, 2) what is the use, if any, of the conflict of laws in interpreting international treaties, 3) the broader question of interrelation between public international law and private international law. Dr Hayk Kupelyants is the Clifford Chance Lecturer in the Conflict of Laws at the University of Cambridge and a Fellow of Homerton College. He is the author of 'Sovereign Defaults before Domestic Courts' (OUP 2018).