A repeal is the removal or reversal of a law. This is generally done when a law is no longer effective, or it is shown that a law is having far more negative consequences than were originally envisioned.
If a campaign for the repeal of a particular law gains particular moment, an advocate of the repeal might become known as a "repealer". This happened in 19th century Britain to a group in favour of the re-separation of Ireland from the United Kingdom
Many repeals are the result of changes in society, such as the old Jim Crow laws or blue laws. Other repeals are for more mundane things,