A remedy under contract developed by the courts of chancery as a way of addressing the manifold injustices of a doctrinaire application of the common law of contract. Sometimes damages ain’t enough, you see (where contractual privity is a harsh mistress; also frequently under a confidentiality agreement).
So, “M’lud I don’t want money. I want this blighter to stop doing what he’s doing, that he promised me he wouldn’t do (injunction), or start doing what he’s not doing, if he said he would (specific performance), or account to me for stuff he shouldn’t have ever got in the first place (restitution) (okay in this case I do want money).”
An injunction is an equitable remedy for breach of contract — or, for that matter, tort, but finance types tend not to care so much about them — that originated in the English courts of equity. Its aim: to stop someone behaving inequitably — to “enjoin” the person so to speak, from indulging in turpitude — thereby providing a redress for wrongs for which an award of money damages — the usual tool in the common law’s armoury — doesn’t quite scratch the itch. An injunction can be given only when there is “no adequate remedy at law” — meaning, principally, the common law, but we suppose it could include statute and regulation as well. Compare with specific performance.
Specific performance one of the great equitable remedies for breach of contract — designed to wrap an innocent, clean-handed contractual counterparty with the warm blanket of the courts of chancery when the cold economic rationalism of the common law leave his moral senses — and those of the Ch.D — still outraged. All it really amounts to is a court order directing a contracting party to do what it has promised to do, where the court has plausible grounds to think that it might not — most likely, where “damages would not be an adequate remedy” — you will hear that phrase chucked about a lot — and the innocent party cannot find someone else to perform the contract in the breaching party’s stead (and thus have a clear and adequate measure of loss for a damages claim).
Restitution — a.k.a unjust enrichment, or money had and received — is a claim made feasible through an imaginative synthesis of long-“forgotten” rules of the common law, dreamt up by Lord Goff to bring justice to little old ladies, welsh hoteliers and others — not, apparently, including financial services conglomerates — who have been dealt a short hand by the cosmic game.
Difficult cases involving such unfortunates (and the odd gambling-addict conveyancer) gave rise to an entire branch of civil law known as restitution, a common lawyer’s duck-billed platypus: an ancient civil action, latterly back in fashion, that sounds neither in contract — there is none — or tort — there has been none — but sits uneasily between them, in its own jurisprudential space, rather like our old friend Bob Cunis: neither one thing nor the other; a sort of law of equity for people who don’t like the law of equity or the floppiness and uncertainty it tends to bring.