The Commonwealth of Australia was established on 1 January 1901 when six self-governing British colonies united to form one nation. This event is known as Federation and the basic rules for the new nation are set out in the Australian Constitution.
Sections 121-124 of the Constitution allow for an increase in the number of states and territories. However, there is no mention of how an existing state or territory could secede (leave or exit) from Australia, and the Preamble to the Constitution states that the Australian federation is “indissoluble” (not able to be broken).
There has only been one major attempt to test the indissolubility of the federation. In 1933 Western Australia held a referendum (public vote) to secede from Australia. The vote was in favour of secession and the Western Australian Government petitioned the British Parliament to be allowed to leave the Commonwealth of Australia. After 18 months of consideration, the British Parliament determined it had no authority to grant secession. As a result, Western Australia remained part of Australia.