The Parliament House website lists all the bills (proposals for new laws or changes to existing ones) that have been introduced into the Australian Parliament since 1996. By searching this webpage you will be able to find out when the bill was introduced, information about the bill and when it received Royal Assent to become law.
All Australian laws are also listed on the ComLaw website. You will need to search by the title of a law or a date. Note: if the Act does not say when the law is to commence (come into effect), it will commence 28 days after it received Assent.
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