Section 109 of the Constitution of Australia

Interaction between federal and state law

Section 109 of the Constitution of Australia is the part of the Constitution of Australia that deals with the legislative inconsistency between federal and state laws, and declares that valid federal laws override ("shall prevail") inconsistent state laws, to the extent of the inconsistency. Section 109 is analogous to the Supremacy Clause in the United States Constitution and the paramountcy doctrine in Canadian constitutional jurisprudence, and the jurisprudence in one jurisdiction is considered persuasive in the others.

The High Court of Australia in D'Emden v Pedder (1904), in the first substantial constitutional case presented before the court, cited and drew on the jurisprudence of the United States case of McCulloch v. Maryland, recognising that the case was not binding. Following the reasoning in the American case, the court adopted the doctrine of implied intergovernmental immunities. In the Engineers Case (1920), the High Court of Australia swept away the earlier doctrines of implied intergovernmental immunities and reserved State powers, firmly establishing the modern basis for the legal understanding of federalism in Australia. The Court also rejected the use of American precedent and said that they would apply the settled rules of construction giving primacy to the text of the Constitution, anchoring interpretation in its express words. In 2003, former Chief Justice of Australia Sir Anthony Mason wrote:

In conjunction with the doctrine outlined in the Engineers Case, it has also significantly extended the reach of Federal legislative power in Australia.

Instances may arise when it is impossible to obey two laws simultaneously. A classical example is R v Licensing Court of Brisbane; Ex parte Daniell. A state referendum on liquor trading hours was fixed by State law for the same day as a federal Senate election. The Commonwealth law provided that a State referendum could not be held on that day. It was held that the State law, to the extent of the inconsistency, was invalid. As Isaacs J. observed:

In some situations, one law may purport to confer a legal right, privilege or entitlement, while another law purports to take away or diminish some right or entitlement. In other words, one law says that you can do X, the other that you cannot do X. For example, the Commonwealth provision in Colvin v Bradley Brothers Pty Ltd affirmed that employers in certain industries could employ women to work on certain machines whilst the State provision made it an offence to do so. It was not impossible to obey both laws, since nothing in the Commonwealth law required the employment of females. This type of inconsistency may require a working out of the actual effect of both laws in an individual case. Because of this, it could require a more subtle analysis than test 1. Similar reasoning was later used in Telstra v Worthing, in discussing conflicting workers' compensation laws, and in Bell Group v Western Australia, where a Western Australia Act that sought to accelerate the dissolution and administration of the Bell Group was held to conflict with the Commonwwealth's income tax laws. Chief Justice Knox and Justice Gavan Duffy agreed in Clyde Engineering Co Ltd v Cowburn that a simple test of logical contradiction was "not sufficient or even appropriate in every case", and enunciated this test: where one statute confers a right, and the other takes away the right, even if the right may be waived or abandoned, there is an inconsistency, whereupon the State law would then be invalid to the extent of the inconsistency.

The Commonwealth can avoid covering a legislative "field" by passing an express provision declaring its intention not to do so. This means in practice that the Commonwealth can control the operation of s.109 in a negative way by making it clear that related State laws are to operate concurrently with the Commonwealth law. The leading case is R v Credit Tribunal; Ex parte General Motors Acceptance Corporation, where Mason J. noted: