A more thorough explanation:

Repeal means to cancel or get rid of an existing law. This can be done by passing a new law or changing the constitution. When a law is repealed, it is no longer in effect and cannot be enforced.

• The Twenty-First Amendment to the U.S. Constitution repealed the Eighteenth Amendment, which had banned the production and sale of alcohol. This ended the era of Prohibition in the United States.
• The National Highway Designation Act of 1995 explicitly repealed the National Maximum Speed Law of 1974, which had set a speed limit of 55 miles per hour on U.S. highways.
• In State v. Davidson, the Idaho Supreme Court found that a later law on negligent homicide had repealed an earlier law on involuntary manslaughter by implication. This means that the two laws were so similar that the later law effectively cancelled out the earlier one.

These examples show how repeal can happen in different ways. Sometimes it is done explicitly, with a new law specifically stating that an old law is no longer in effect. Other times, it happens implicitly, when a new law conflicts with an old one and effectively cancels it out.