The cessation of use; disuse; discontinuance of practice, custom, or fashion.

a state of inactivity or disuse

In law, desuetude (from the French word désuet, outdated) is a doctrine that causes statutes, similar legislation or legal principles to lapse and become unenforceable by a long habit of non-enforcement or lapse of time; it is what happens to laws that are not repealed when they become obsolete.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 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.