New horizons for the law of armed conflict—the adjudication of international humanitarian law before investor–State tribunals

Abstract Past investment treaty arbitrations (ITAs) that have arisen out of armed conflicts in Libya and Ukraine, as well as the current geopolitical climate, highlight the increasing relevance of international humanitarian law (IHL) before investor–State tribunals. Whilst previous scholarship has focused primarily on the legal bases upon which tribunals may consider IHL, this article examines both the legal and, more importantly, the theoretical foundations for its consideration in ITA. It first provides a brief overview of the ITAs in this field, and then addresses the legal basis on which IHL may be taken into account in ITA. As its principal contribution, the article proceeds to examine the theoretical relationship between IHL and international investment law. It argues that, notwithstanding their apparent differences, the two regimes share important historical, structural, and normative points of convergence which support their concurrent consideration in ITA. The fifth part of the article addresses some of the practical difficulties that investor–State tribunals might face in considering IHL in ITA, and argues that the procedural flexibility of ITA enables such challenges to be addressed. Overall, the article demonstrates that there are strong legal and theoretical bases for the consideration of IHL in ITA.