Restitution beyond Contract and Tort: Mapping Its Autonomous Domain in Contemporary Jurisprudence

Abstract

This paper explores the theoretical underpinning and the scope of restitution as an independent body of law. It takes a comparative look at the law of unjust enrichment in Anglo-American common law, civilian jurisdictions and argues that it is a third pillar of the law of obligations – with its very own organizing principle and internal taxonomy, as well as remedial logic. The historical story of restitutionary liability, from the Roman condictiones to quasi-contractual fictions of the common law, to the arrival of the modern analytical approach in Lipkin Gorman v Karpnale Ltd (1991) is mapped. It critically maps the four defining elements of an unjust enrichment claim enrichment, at the expense of the claimant, unjust factor, and defenses and analyses their interaction with contractual and tortious doctrines without collapse into either. The paper also interrogates the proprietary dimension of restitution, the role of subjective devaluation, the nature of enrichment by services, and the continuing controversy over the recognition of 'absence of basis' as an alternative structuring principle. Finally, the paper situates restitution within broader debates about the coherence of private law and considers its trajectory across England and Wales, the United States, Australia, Canada, and Germany.