The state of being unused; legally, the doctrine by which a law or treaty is rendered obsolete because of disuse. The concept encompasses situations in which a court refuses to enforce an unused law even if the law has not been repealed.
Desuetude saw use as a defense during the U.S. Supreme Court's landmark 2003 decision in Lawrence v. Texas, which dealt with Texas' Sodomy law. Lawrence successfully argued that since statutes prohibiting sodomy had either fallen into obscurity or been overturned in most states, Texas' statute was similarly invalid.
DESUETUDE. This term is applied to laws which have become obsolete. (q.v.)