Courts and commentators frequently use the noun ‘subsidiarity’ and the adjective ‘subsidiary’ to help explain certain of unjust enrichment’s relations with other areas of law – especially property, contract, and statute. However, the vocabulary of subsidiarity is unsuited for that purpose. It should disappear from unjust enrichment discourse. After a brief introduction, this paper proceeds in four further sections. Sections II and III analyse accounts of unjust enrichment as subsidiary to property and contract. They show that the instances in which unjust enrichment claims are said to be subsidiary to property and contract are ones in which a given enrichment is not unjust in the first place. This means that they are situations where, as a matter of law, no unjust enrichment claim actually exists to be subsidiary to any other claim or institution. They cannot logically, therefore, represent examples of the so-called subsidiarity of unjust enrichment. They are better explained through the spectrum of the ‘unjust question’ in the unjust enrichment inquiry. Section IV applies the same arguments to the interaction of unjust enrichment and statutes which are entirely inconsistent with unjust enrichment claims. It also demonstrates that unjust enrichment is not subsidiary to statutes which, though not exclusive of unjust enrichment, nevertheless alter its normal operation. Section V concludes.
Campbell, Mat, Doubting the Subsidiarity of Unjust Enrichment (July 18, 2020).