Restitution and Equity: An Analysis of the Principle of Unjust Enrichment

The law of restitution is said to embody a principle against unjust enrichment: one person should not be unjustly enriched at the expense of another. This article is a study of the principle against unjust enrichment and its connection, if any, to "equity." The principle against unjust enrichment can be understood in at least three ways. First, it can be interpreted as a principle of Aristotelian equity, providing correction when normally sound rules produce unjust results in particular cases. Second, the principle against unjust enrichment can be characterized as a "legal principle" incorporating a broad ideal of justice, from which courts can deduce solutions to particular restitution problems. Finally, the principle can be understood simply as expressing a common theme of restitution cases; on this view, unjust enrichment is a descriptive and organizational concept, which plays no direct role in judicial decision-making. The first two interpretations associate unjust enrichment, and hence the law of restitution, with equity. The third view does not imply a special affinity between restitution and equity, in contrast to other areas of law. The article concludes that restitution should not be confused with Aristotelian equity, because there is nothing both unique to restitution and common to all instances of restitution that justifies courts in according less respect to rules than they would in other areas of law. Although the second interpretation of the principle against unjust enrichment, as a principle from which courts can deduce outcomes, is more plausible, it seems unwise to confer authoritative legal status to a notion as vague as unjust enrichment. Accordingly, the third interpretation is the most appealing.