University of Pennsylvania Journal of International Law

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States are often enriched by the flow to their coffers of wealth accrued to private actors through internationally harmful conduct such as overfishing, acts causing transboundary air or marine pollution, cyber attacks, and international corruption. A portion of the wealth acquired by private actors through such conduct is often passed on to the State through its tax system. This article argues that this form of income to the State triggers the application of the international norm against unjust enrichment. Under the international law of unjust enrichment, such income could give rise to a duty of restitution owed by the enriched State to any State harmed by the conduct of the private actors.

This article argues that the purposes of the norm against unjust enrichment – promoting individual justice between parties and removing incentives for wrongful conduct – require its application in international law to the indirect enrichment of a State as a result of internationally harmful conduct by its taxpayers. Such application of the international norm against unjust enrichment is particularly important because of (a) evidentiary difficulties in the international arena, which significantly erode the efficacy of the remedial regime that is based on the rules concerning the responsibility of States for internationally wrongful conduct; (b) the unavailability in international law of a cause of action against private actors engaging in internationally harmful conduct; and (c) the limited capacity of a State harmed by the conduct to recover from such actors under its domestic legal system. The article suggests that the purview of the international norm against unjust enrichment extends to situations of an indirect link between the loss of the claimant State and the gain of the enriched State, provided that such link is sufficiently close.