Term for law that is not practiced in reality

I am looking for a (legal) term that describes the following concept: A law that should describe the reality of a situation, but in practice, since the law is not enforced, reality is not so. One example would be: Congress passed many laws during the post- Civil War era protecting the rights of African Americans, but since Redeemer government not only disrespected these laws but passed legislation against them, these federal laws were a reality solely on paper.

Thanks

It is called dead letter. Per Cambridge Online

: a ​law or ​agreement that is no ​longer ​effective:

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 The concept encompasses situations in which a court refuses to enforce an unused law even if the law has not been repealed.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 .]