Before 1901, Australia was made up of six separate, self-governing British colonies.

Within its borders, each colony had its own constitution and its own laws relating to defence, immigration, postage, trade and transport. People wanted to unite the colonies to form a single Australian nation for a number of good reasons. Enforcing the law across borders was difficult. The separate colonies also had weak systems of defence. More importantly, Australia had outgrown its humble beginnings and a sense of patriotism and national identity was rapidly taking shape.

On January the First, 1901, when the Constitution took effect, the Australian colonies became one independent nation, known as the Commonwealth of Australia. The Commonwealth of Australia Constitution Act of 1900 is the legal document that sets out the basic rules binding the government of Australia.

The Australian Constitution established the form of the Parliament, created with a House of Representatives and a Senate. It also established the High Court of Australia, which has the ultimate power to apply and interpret the laws of Australia. The Australian Constitution can only be changed through a special vote called a referendum.

In a referendum, there needs to be a “double majority” for the Australian Constitution to be changed. This means that the majority of voters in a majority of states across the nation must vote for the change expressed in the question asked at the referendum.