Desuetude

In law, desuetude (/dɪˈsjuːɪˌtjuːd/ or /ˈdɛswɪtjuːd/; from the French: désuétude, from the Latin: desuetudo English: outdated, no longer custom) is a doctrine that causes statutes, similar legislation or legal principles to lapse and become unenforceable by a long habit of non-enforcement or lapse of time. It is what happens to laws that are not repealed when they become obsolete. It is the legal doctrine that long and continued non-use of a law renders it invalid, at least in the sense that courts will no longer tolerate punishing its transgressors.

The policy of inserting sunset clauses into a constitution or charter of rights (as in Canada since 1982) or into regulations and other delegated/subordinate legislation made under an Act (as in Australia since the early 1990s) can be regarded as a statutory codification of the common-law doctrine.

The doctrine of desuetude is not favoured in the common law tradition. In 1818, the English court of King's Bench held in the case of Ashford v Thornton that trial by combat remained available at a defendant's option in a case where it was available under the common law. The concept of desuetude has more currency in the civil law tradition, which is more regulated by legislative codes, and less bound by precedent. The doctrine went into decline after the Middle Ages when the idea that the need for the king's assent to nullify a law became prevalent.

...
Wikipedia