The Australian Constitution: WACE Year 12 Politics and Law
“Analyse the role of the Australian Constitution in dividing power, distributing authority and enabling change”
The Australian Constitution is the supreme legal document that created the federal system in 1901. It divides law-making power between the Commonwealth and the states, separates legislative, executive and judicial power, and can only be changed by a referendum under section 128.
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.
Section 109 only operates where both laws are otherwise valid and they genuinely conflict. It does not give the Commonwealth power it does not already have under section 51; it simply decides which valid law wins. This distinction is frequently tested.
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.
Step 1: Set up the two jobs
State that the Constitution does two things at once. It distributes power (between levels of government and between branches) and it limits power (through inconsistency, rigidity and rights). Signposting both halves earns structure marks.
Step 2: Show distribution with sections
Explain that section 51 lists the Commonwealth heads of power (trade, defence, external affairs, corporations), mostly concurrent, while residual powers (criminal law, education, health) stay with the states. Add that Chapters I to III split legislative, executive and judicial power.
Step 3: Show limitation with sections
Explain section 109 (valid Commonwealth law prevails over an inconsistent state law), section 128 (only a double-majority referendum can amend the text, so Parliament cannot expand its own power), and the handful of express rights (s80, s116) plus implied limits.
Step 4: Tie back to limited government
Conclude that these features together make Australia a system of limited constitutional government rather than unlimited parliamentary power, enforced by High Court judicial review.
A common error is treating the Constitution as just another Act of Parliament that Parliament can amend. It cannot. Ordinary legislation is made and changed by Parliament alone, but the Constitution can only be altered by the section 128 referendum process requiring a double majority of the people. Another frequent slip is saying section 51 gives the Commonwealth "all" power; section 51 is a closed list, and everything not listed is a residual power left to the states.
Exam-style questions
Questions in the style of SCSA exam questions on this dot point, each with a worked answer. They are written by ExamExplained unless tagged "Past paper"; the year shows the paper a question is modelled on.
WACE 2021-style8 marksExplain how the Australian Constitution both distributes and limits political and legal power.Show worked answer →
An 8 mark response needs distribution, limitation, and worked detail on each.
Distribution. The Constitution federates Australia, dividing law-making power between the Commonwealth (the section 51 enumerated heads of power, mostly concurrent) and the states (residual powers such as criminal law, education and health). It also distributes power between three branches across Chapters I, II and III (legislature, executive, judicature), embedding the separation of powers.
Limitation. Power is limited in several ways: section 109 makes a valid Commonwealth law prevail over an inconsistent state law; the Constitution is rigid and can only be altered by a section 128 double-majority referendum, so Parliament cannot expand its own authority; and a few express rights (s80 jury trial, s116 religion) plus implied limits restrain the Commonwealth.
Markers reward accurate use of sections (51, 109, 128) and the link between structure and limited government.
WACE 2023-style6 marksDescribe the process for altering the Australian Constitution under section 128 and assess why so few referendums have succeeded.Show worked answer →
A 6 mark response needs the process and a reasoned assessment.
Process. A proposed alteration must pass both houses by absolute majority (or one house twice in limited cases), then be put to electors, where 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 six).
Assessment. Only eight of 45 proposals have succeeded because the double majority is deliberately demanding, bipartisan support is usually required, voters are cautious about giving Canberra more power, and confusing or poorly explained questions tend to fail. The 2023 Voice referendum failed without a majority in any state.
Markers reward the double-majority detail and at least two reasons for the low success rate.