Causation in the Law of State Responsibility and the Problem of Overdetermination: In Search of Clarity

This article addresses the preliminary steps that must be taken in order to study the problems stemming from overdetermination in the law of state responsibility. Overdetermination, broadly defined, is the existence of multiple causes (multiple wrongdoers, external natural causes, contribution to the injury by the victim and so on) contributing towards a harmful outcome. As relationships among states become more and more complex, there is a corresponding increase in the complexity of the potentially harmful outcomes of these relationships. The fact that the harm caused may originate in diverse sources (overdetermination) poses challenges to the law of state responsibility. These challenges pertain to most aspects of state responsibility, yet their dimension regarding causality has not been studied in depth. The confusion surrounding causal analysis conducted by international adjudicatory bodies leads to decisions that are not convincing in their determination of responsibility in causal terms. The argument of the article is twofold. First, it holds that the concept of causation in international law is unclear, especially in relation to overdetermination, and it must be clarified. Second, it holds that a clearer concept of causation can provide useful guidance to the decision-making process of international courts and tribunals: the clear and principled application of causal tests will, in turn, lead to clearer reasoning. A clearer judicial reasoning will improve the foreseeability of the judicial outcome, will provide better guidance for the parties before a court and will lead to a fairer judicial