Shared responsibility in international law, a conceptual framework

his paper explores the phenomenon of the sharing of international responsibilities among multiple actors who contribute to injury to third parties. It examines the manifestations of shared responsibility, identifies the normative questions that it raises, assesses its possible consequences for international law and legal doctrine and sets forth a conceptual framework that allows us to analyze questions of shared responsibility. By doing so, the paper lays out the foundations, scope and ambitions of the SHARES Project - a five-year research project funded by the European Research Council and carried out by a research group at the Amsterdam Center for International Law.

The paper more particularly explores the current framework of international state responsibility, how it can apply to situations of shared responsibility and what are its limits. It then suggests revisiting the foundations of international responsibility and proposes, in light of its public/private nature and objectives to move away from a unitary to differentiated regimes of international responsibility. It is within this new framework that some key normative questions, both substantial and procedural, that arise in situations of shared responsibility are discussed (joint and several liability, relationship between multiple wrongdoers, changes to the bilateral nature of international dispute settlement).

The paper concludes with a 'semantic toolbox' of shared responsibility, defining concepts such as 'shared accountability', 'shared attribution or 'shared liability' which will provide a useful point of reference for subsequent research on the topic.