The legal system follows the common law tradition.
The Queen of Australia is Head of Government, and she appoints a Governor General - on advice of the central Commonwealth Government - to be her representative.
The Australian Parliament (in Canberra, ACT) enacts Federal laws. It is made up of two houses- the House of Representatives and the Senate.
The office of Prime Minister is held by the leader of the party with a majority in the House of Representatives, on appointment by the Governor General.
Alongside the commonwealth legal system Australia has a federation of six States and three self-governing territories, each with their own constitutions, parliaments and laws.
The distribution of powers between the federal and state governments are laid out in the Australian Constitution (63 & 64 Victoria, c.12), which first came into force in 1901.
Free resource. Commonwealth of Australia and Australian Government Gazettes from October 2012 onwards are available as individual notices in HTML, Word and PDF
Law and Justice in Australia : foundations of the legal system by 