My view is that the truth is almost exactly the opposite of this. It is true that the sort of reasons that a court, including a Supreme Court, can bring to bear in reaching a decision are much more circumscribed than those of a legislature. But judges observably change the law. The common law is observably not the same as it was in 1700 and all of the changes cannot be ascribed to changes in society or the correction of mistakes. Someone changed it, and it wasn't elves.

The role of the judge in interpreting the law is like that of a painter working on a vast canvas which has been, is being and will be worked on by others. The judge is trying to paint the best picture of the law that he can. The judge is not free, unlike a legislature, to whitewash over any area of the painting as he sees fit and start again. A judge is never painting on an entirely blank piece canvas. But, the best picture which can be painted changes. As the picture develops, as the strokes of judicial decisions are added over time, early work which once fitted may no longer do so and may need to be painted out. every judicial decision, however trivial, changes the law, even if only in an infinitesimal way. After DMG v IRC future judges are faced with a new picture that includes that decision. Even a banal decision which simply follows earlier authority adds strength to it which should influence future judges in deciding whether to continue to follow the standard set down.

We must accept that the law changes as a result of judicial decisions. If such changes are given retrospective effect, which they are, so that they apply to events prior to the time of judgment, it must be accepted that our commitment to the rule of law is not absolute.

Robert Stevens

Charles Mitchell writes:

Re 2a: I'm afraid that I disagree with Jason and Robert that the only source of difficulty here is the artificiality of saying that the payor was mistaken. Problems also flow from the fact that the content of law is an objective social fact that can be determined at any given moment. The question whether the law requires X to pay Y in a given situation may sometimes be difficult to answer because the law is uncertain, but suppose that we know the answer because a judicial decision gives us a clear 'yes'. If X pays Y pursuant to the rule and then seeks to recover his payment, then Y can say that the rule established by the case constitutes a legal ground for the transfer. If X pays Y, and then in a different case the rule is overturned, it is fictional to say that X can now recover from Y because there never was a legal ground for X's payment because there never was a rule requiring the payment. To say that there is no fiction 'because the law can be changed with retrospective effect' (Rob) is mere assertion, and to say that 'the judges are for the most part stating what they think the law always demanded' (Jason) does not really meet the point. I don't deny that the courts (and Parliament) have the power to deem there never to have been a legal ground for X's payment if they want to - but I want them to tell me explicitly why they think this is a good idea, and I don't think it's wise to let them off the hook by telling them that repayment just follows 'automatically'.