In December last year, the 8th edition of the seminal work on the law of restitution by Goff & Jones was published (by Sweet & Maxwell – ISBN 9781847039101); only it is no longer edited by either Goff or Jones, or entitled, as formerly, “The Law of Restitution”, taking up the new (and one might say more trendy) name, “The Law of Unjust Enrichment”.
The new authors (lead by Professor Charles Mitchell, who takes over from Gareth Jones for this edition) explain their reasoning for breaking with several decades of naming tradition on the basis that “restitution” describes the law’s response to an event, whereas they wish to focus on the event itself, which is best classed as “unjust enrichment”. Further, they write, unjust enrichment can have responses other than restitution, and restitution can be invoked by events other than unjust enrichment. Indeed, this latter category had formerly been covered by the work, but the section on what had become known as “restitution for wrongs” (such as the recovery of bribes in private civil proceedings) has been excised from this latest version for this reason, although the authors promise a separate work covering this topic in the future.
What is now recognised as “unjust enrichment”, the authors explain, was once scattered across disparate corners of the law, appearing as the obfuscatorily labelled “quasi-contract”, the action for money had and received, or (in the case of an agent), money paid to the use of another and the actions of quantum meruit and quantum valebat, and no common principle underlying them recognised. In more recent times, first academics and then judges came to recognise these various individual rules as being part of a more general principle of unjust enrichment, that a person should not be unjustly enriched at the expense of another. The relief given by the law in cases traditionally classified as for money had and received (such as a person finding a lost banknote and paying it into his own bank account, mixing it with his funds) and quantum valebat (a person taking ownership of goods other than under a contract or by way of gift and in circumstances in which the transferor ought be entitled to payment) has more recently been classified under the more general heading of “unjust enrichment”. The recognition of the more general principle of unjust enrichment, extending outside these categories, was first made by the English courts in Lipkin Gorman v Karpnale Ltd  2 A. C. 548 (H. L.), where a casino was made to repay bets placed with it (which, being payments in the course of gambling, were not pursuant to enforceable contracts) by an individual who had, unbeknownst to the operator of the casino, embezzled the funds that he was gambling form his employer, a firm of solicitors. The court granted relief (subject to the casino being entitled to set off prizes that it had paid to the embezzler, pursuant to the defence of change of position, also recognised for the first time in that case) despite the case not fitting into any of the hitherto well recognised categories of claims for restitution.
Whilst the principle so simply stated seems impossibly broad and vague, the law of unjust enrichment as it is actually applied is neither: the requirement that the enrichment of one “at the expense of” another is narrowly interpreted such as to require some direct transfer of value – usually money, but sometimes goods or services – from the claimant to the defendant. Indeed, the law of unjust enrichment is set about with so many detailed rules about precisely what can be recovered when that it is as predictable and intricate as the law of tort or contract. This is by no means a bad thing: it would be a disorderly and unworkable system of justice if, for example, a business person was able to claim that a rival unjustly enriched itself at her or his expense by undercutting her or him, or that wealthy people are unjustly enriched at the expense of the poor by not giving more money to charity – whatever one’s political views on these questions, these are not questions properly answered by the private law of obligations.
That is all very well in so far as it goes, but one cannot help but wonder whether the category of “unjust enrichment” properly understood as a category of the highest degree of generality into which a whole range of sets of detailed rules that have in common the reversal of unjust enrichment at the expense of another (and not necessarily anything else) is so broad a category as to be of only limited usefulness. Indeed, it might be said that it is as meaningful and useful as an equivalent category of “unjust impoverishment” covering all cases in which a person unjustly suffers loss as a result of another’s legal wrong, into which all manner of hitherto separately treated areas of law, such as breach of contract, tort, breach of trust, unfair dismissal and doubtless many others could be lumped and covered by a single omnibus work bearing that title, and explaining that, until recent academic analysis, these areas were thought to be entirely distinct but that they really should be treated as all instances of the same thing, and that the fact that the category is not closed was recognised by the House of Lords in Caparo Industries plc v. Dickman  2 AC 605 (the relevance of this case being one specifically on negligence being the same as the relevance of the Lipkin Gorman case being specifically on money had and received).
In any event, is it not worthwhile or meaningful to have a work dedicated to the principles of law involved in what the new authors of Goff & Jones term a “response”? If Professor Mitchell thinks not, he might wish to explain that to the authors of McGregor on Damages (also published by Sweet & Maxwell), who have not yet, apparently, got the message.