What is "desuetude"

Desuetude \Des"ue*tude\, n. [L. desuetudo, from desuescere, to grow out of use, disuse; de + suescere to become used or accustomed: cf. F. d['e]su['e]tude. See Custom.] The cessation of use; disuse; discontinuance of practice, custom, or fashion.

The desuetude abrogated the law, which, before, custom had established.
--Jer. Taylor.

1620s, from Middle French désuétude (16c.), from Latin desuetudo "disuse," from desuetus, past participle of desuescere "become unaccustomed to," from de- "away, from" (see de-) + suescere "become used to" (see mansuetude).

n. disuse, obsolescence (for example, the state of a custom that is no longer observed nor practised)

n. a state of inactivity or disuse

In law, desuetude ( or ; from the , from the ) 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 It is what happens to laws that are not repealed when they become obsolete.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.