Analyse the role of the Australian Constitution in dividing power, distributing authority and enabling change

What this dot point is asking

The Commonwealth of Australia Constitution Act 1900 (UK) came into force on 1 January 1901 and remains the legal foundation of the Australian political system. SCSA wants you to understand it as a working document that does three big jobs: it distributes power, it limits power, and it provides a controlled way to change power.

The Constitution is structured into eight chapters. Chapter I deals with the Parliament (the Senate, the House of Representatives and the legislative power), Chapter II with the executive government, and Chapter III with the judicature (the courts). This structure embeds the separation of powers, although in practice the legislature and executive overlap because Australia uses responsible government, where ministers must sit in Parliament.

The division of powers

The Constitution creates a federation, so it divides law-making authority between two levels of government. Section 51 lists the specific (enumerated) heads of power the Commonwealth Parliament can legislate on, such as trade and commerce, defence, taxation, external affairs and corporations. Most of these are concurrent powers, meaning both the Commonwealth and the states can legislate on them. A smaller set are exclusive powers belonging only to the Commonwealth, such as coining money (section 115) and customs and excise duties (section 90).

Powers not listed in the Constitution remain with the states. These are called residual powers and cover areas such as criminal law, education, health and public transport. This is why criminal law differs between Western Australia and other states.

When a valid Commonwealth law and a valid state law conflict on a concurrent matter, section 109 resolves the clash: the Commonwealth law prevails and the state law is invalid to the extent of the inconsistency. Section 109 is a major reason Commonwealth power has expanded over time.

Changing the Constitution: section 128

The Constitution is rigid, meaning it cannot be changed by ordinary legislation. Section 128 sets out the referendum process. A proposed alteration must first be passed by an absolute majority in both houses of federal Parliament (or by one house twice in limited circumstances). It is then put to electors, and to succeed it must achieve a double majority: a national majority of all voters, and a majority of voters in a majority of states (at least four of the six states).

This is a deliberately demanding test. Of the 45 proposals put since 1901, only eight have succeeded. Notable successes include the 1967 referendum (allowing the Commonwealth to make laws for Aboriginal people and to count them in the census) and the 1977 referendums on retirement age for judges and territory voting. The 1999 republic referendum and the 2023 Aboriginal and Torres Strait Islander Voice referendum both failed, the latter not achieving a majority in any state.

Interpretation by the High Court

The Constitution is also shaped by how the High Court interprets it. Because the text is brief and old, the meaning of heads of power evolves through case law. The Engineers' Case (1920) established that Commonwealth powers should be read broadly according to their natural meaning, ending the earlier doctrine of implied intergovernmental immunities. The Tasmanian Dam Case (1983) confirmed the external affairs power (section 51(xxix)) lets the Commonwealth legislate to give effect to international treaties, dramatically widening federal reach. This judicial interpretation is why studying the Constitution always means studying the High Court alongside it.

A final framing point: the Constitution does not contain a comprehensive bill of rights. It protects only a handful of express rights, such as the right to trial by jury for some federal offences (section 80) and freedom of religion (section 116), plus a few rights the High Court has implied, most importantly the implied freedom of political communication.