There are many reasons why the Australian Parliament might agree to repeal—undo or remove—an existing law; the law might be outdated or the government might want to address an issue differently.
Repealing a law requires the same process as making a new law. A repeal bill—proposed law—must be debated and agreed by both the Senate and House of Representatives before it is signed into law by the Governor-General. The repeal bill will state when it comes into force.
Some laws do not need to be repealed because they have an expiry date called a sunset clause. All delegated law made by ministers and government departments has an expiry date unless the Parliament decides to renew it.