The Structure and Content of the Right for Restitution for Unjust Enrichment

I Introduction

John Austin held that the principal analytic distinction to be drawn in the law of obligations is that between primary and secondary rights and duties.¹ Secondary rights and duties, on Austin's account, are those that arise from violations of other rights and duties, or, as he variously puts it, from delicts or injuries.² Primary rights and duties are those that do not arise from violations of other rights and duties.³ Conjoining this distinction with the principle that 'every right of action arises from an injury, or violation of some other rights'⁴ gives us what, on Austin's telling, is the basic structure of actions in private law. A civil action is, or perhaps asserts, a claim that the defendant is under a secondary duty to set right the effects of a breach of a primary duty correlative to a primary right held against her by the plaintiff.

Austin excepts, with some reservations, one category of case from this account: that comprising those cases 'in which a right of action is given, although there has been no wrong, on account of the want of wrongful consciousness on the part of the defendant.'⁵ An example is a claim for the return of money paid and received under a mistake. In such a case, '[s]o long as the unconsciousness lasts, the possessor is not guilty of a wrong, but lies under a quasi-contract to restore. So soon as consciousness arises, he is guilty of a wrong.'⁶ It is not clear whether Austin held that this subsequent wrong is what anchors the cause of action. That would reconcile the action for the recovery of mistaken payment with the general principle that 'every right of action arises from an injury, or violation of some other rights.' But it would do so at the expense of defining away the category that Austin introduced the case of mistaken payment to illustrate, namely cases 'in which a right of action does not presuppose an injury.'⁷

I think that Austin was undecided. In notes for an undelivered lecture on contract and quasi-contract, he returns to the case of mistaken payment and characterizes it as follows:

[T]he fact of my having received money through a mistake, is not a delict; but begets an obligation to repay that money or an equivalent. And the refusal (express or indicated by conduct) to repay, is the immediate cause of action: i.e., is a delict.⁸

This 'immediate cause of action,' it would seem, asserts a secondary right. Perhaps that is the answer. But Austin then adds 'Or the action may be considered a vindication'⁹ - that is, an enforcement of the payee's primary duty to repay.

Mistaken payment is the paradigmatic example of an action in what is now (most often) called the law of unjust enrichment. Austin's puzzle foreshadows a present-day debate over the question of whether the right to restitution for unjust enrichment is a primary or a secondary right, or, equivalently, whether the duty to make restitution for unjust enrichment is a primary or a secondary duty. I will say that this question asks what the structure of the right to restitution is. Here I will defend an answer to this question, and draw from it certain implications for the justification of liability in unjust enrichment, some of which cast doubt on the widely held view that an action in unjust enrichment expresses a claim in corrective justice. We will see that sorting out the structure of the right to restitution for unjust enrichment requires considering to what, exactly, it is a right. I will say that this latter question asks what the content of that right is. The answer, we will see, bears on the question of the place of unjust enrichment in private law as a whole, a question I will take up in conclusion.

II The paradigmatic case

Let us begin with a closer look at the core case of unjust enrichment, mistaken payment. The paradigmatic claim in...