The Australian Constitution is the set of rules by which Australia is run. The first three chapters of the Constitution define three largely separate groups - the Parliament, the Executive and the Judiciary - and the roles they play in Australian governance. The powers to make and manage federal law is divided between these three groups. This division is based on the principle of the 'seperation of powers'. This fact sheet explains the seperations of powers in Australia.

http://www.peo.gov.au/students/fact_sheets/separation_powers_parliament_executive_judiciary.html