Derogation is a legal term of art, which allows for part or all of a provision in a legal measure to be applied differently, or not at all, in certain cases. The term is also used in Catholic canon law,^{[full citation needed]} and in this context differs from dispensation in that it applies to the law, whereas dispensation applies to specific people affected by the law.

Black's Law Dictionary defines derogation as "the partial repeal or abolishing of a law, as by a subsequent act which limits its scope or impairs its utility and force". It is sometimes used, loosely, to mean abrogation, as in the legal maxim lex posterior derogat priori ("a subsequent law derogates the previous one").

According to West's Encyclopedia of American Law, derogation "implies the taking away of only some part of a law", or it is a "partial repeal of a law, usually by a subsequent act that in some way diminishes its original intent or scope", so distinguished from annulment, defined as the destruction of the law by "an act of the legislative power, by constitutional authority, or by usage". Black's also distinguishes from what it calls "abrogation, which means the entire repeal and annulment of a law".

In the law of treaties, derogation means the setting aside of some provision or requirement of the treaty. The party to the treaty is said to have "derogated from" that provision.

In human rights law, the term may carry the additional meaning of a national legislature suspending an obligation for a legitimate objective, usually a national security exception or some other extraordinary circumstance relating to the maintenance of public order.

In the conflict between English common law and ecclesiastical courts, both existed as legal systems of equal validity in one geographic space. By the mid 14th century the English Parliament had attempted to limit ecclesiastical jurisdiction with the Statute of Praemunire. Based on the legislation, litigants in ecclesiastical courts argued that canon law, under the authority of Rome, was a derogation of the rights of the English crown, and argued for damages and criminal penalties under that statute.

After the Reformation, appealing to the Roman (or "spiritual") jurisdiction was considered punishable as an offence in derogation of the king's authority. Edward Coke argued that derogating from the common law was the same as diminishing the authority of the King. According to Coke, the royal power had been undermined by the ecclesiastical jurisdiction: "the pope had usurped spiritual jurisdiction of this realm in derogation of the imperial crown of the king." Coke defended royal supremacy in De Iure Regis Ecclesiastico in a historical commentary of the common law's protection of royal authority against papal subversion.

There is a legal maxim: Statutes in derogation of the common law are to be strictly construed. This is also called the "derogation canon". After the American Civil War legislation started to become more important, and some people saw common law as a way of expanding and discovering new rights under the Due Process Clause jurisprudence. Others thought that legislative statutes that changed common law ought to be narrowly interpreted without expansion, as the derogation canon suggested. This became a source of political conflict. Henry Campbell Black (of Black's Law Dictionary) wrote: