JUSTIFYING THE UNJUST ENRICHMENT PRINCIPLE
Even though the unjust enrichment principle has been clearly recognized at the highest level in England, the location of that principle within the law of obligations and the identification of its function still require careful justification.
(A) THE PLACE OF UNJUST ENRICHMENT WITHIN THE LAW OF OBLIGATIONS
The unjust enrichment principle has a vital and distinct role within the law of obliga- tions. Whenever it can be shown that the defendant has been unjustly enriched at the expense of the claimant the defendant will be obliged, by operation of law, to restore to the claimant the value of the benefit which the defendant has received. Consequently, liability for unjust enrichment is properly regarded as falling within the law of obligations and it should be treated as being on a par with the law of tort and law of contract. But, crucially, liability for unjust enrichment is very different from these other aspects of the law of obligations, hence the justification for treating it separately. The law of tort is concerned with the identification of wrongdoing, whereas liability for unjust enrichment does not depend on proof of any wrong. Equally, whereas liability for breach of contract arises from the agreement itself, liability for unjust enrichment is imposed by operation of law and does not depend on any agreement having been made between the parties. Indeed, liability for unjust enrichment will be excluded if a contract between the parties is subsisting.
-  AS Burrows, ‘Contact, Tort and Restitution—A Satisfactory Division or Not?’ (1983) LQR 217.
-  This was recognized by Lord Wright in Fibrosa Spolka Akcyjna v Fairbairn Lawson Combe Barbour Ltd AC 32, 61. See also Banque Financiire de la Cite v Parc (Battersea) Ltd  1 AC 221, 227 (LordSteyn) and Restatement Third: Restitution and Unjust Enrichment (American Law Institute, 2011), 3.
-  See p 134, below.