What is constitutional law?

Constitutional law in Australia is the body of law that interprets and applies the Australian Constitution and related constitutional documents. It covers the structure of government, the relationship between the Commonwealth and the states, the rights and limitations expressed or implied in the Constitution, and the operation of the federal judiciary.

The principal source of Australian constitutional law is the Australian Constitution, contained in section 9 of the Commonwealth of Australia Constitution Act 1900 (Imp). Other constitutional documents include the various state constitutions, the Letters Patent for the offices of Governor-General and state Governors, the Statute of Westminster Adoption Act 1942, the Australia Acts 1986, and the Constitution Alteration Acts that have been passed at referendums.

The High Court of Australia is the final interpreter of the Constitution. Major cases that have shaped Australian constitutional law include Engineers Case (1920, which established the broad reading of Commonwealth heads of power), Communist Party Case (1951, which struck down the Menzies government's attempt to ban the Communist Party), Australian Capital Television Case (1992, which recognised the implied freedom of political communication), Mabo (1992, which ended terra nullius), Wik (1996, which established that native title can coexist with pastoral leases), the Tasmanian Dams case (1983, which upheld broad federal external affairs power), and the dual citizenship cases of 2017 to 2018.

Constitutional law also covers the implied freedoms recognised by the High Court where the structure of the Constitution requires them. The implied freedom of political communication (recognised since 1992) limits Parliament's power to restrict communication on government and political matters. The implied right of all eligible citizens to vote (recognised in Roach v Electoral Commissioner 2007 and Rowe v Electoral Commissioner 2010) limits Parliament's power to exclude categories of voters. The Kable principle (from Kable v DPP 1996) limits Parliament's power to give courts non-judicial functions incompatible with their Chapter III role. Australian constitutional law continues to develop through ongoing High Court cases addressing novel questions about federal and state power.