The concept presented by your example is described by the legal term 'desuetude'. In law, 'desuetude' constitutes a doctrine with this nutshell definition:
The exceptional doctrine of judicial abrogation of a criminal statute where there has been a long period of non-enforcement.
(From Duhaime's Law Dictionary.)
A more detailed legal definition of the 'desuetude' doctrine:
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 The concept encompasses situations in which a court refuses to enforce an unused law even if the law has not been repealed.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. (n.d.) West's Encyclopedia of American Law, edition 2. (2008). Retrieved November 25 2015 from http://legal-dictionary.thefreedictionary.com/desuetude .]
The general use of 'desuetude' (that is, not the specifically legal term) is this:
A state of disuse or inactivity.
[desuetude. (n.d.) American Heritage® Dictionary of the English Language, Fifth Edition. (2011). Retrieved November 25 2015 from http://www.thefreedictionary.com/desuetude .]