Repealing a law means to rescind or annul an existing law by subsequent legislation or constitutional amendment. It can be explicit or implicit. Explicit repeal occurs when a legislative body repeals existing legislation through the jurisdiction’s constitutionally proscribed legislative process. For example, in 1933, Congress passed the 21st Amendment which explicitly repealed the 18th Amendment, thereby ending the prohibition on the production or importation of alcohol. Implicit repeal, also referred to as repeal by implication, occurs when a legislative act conflicts with an existing law but the legislature did not explicitly repeal the existing law. While the later act supersedes the existing ones, effectively repealing it, courts generally disfavor construing legislative acts to implicitly repeal existing laws.

To repeal any element of an enacted law, Congress must pass a new law containing repeal language and the codified statutes location in the U.S. Code (including the title, chapter, part, section, paragraph, and clause) . In this way, Congress (and the president) must follow the same rules and procedures for passing any law. When statutes are repealed, their text is simply deleted from the Code and replaced by a note summarizing what was repealed.