Section 109 of the Constitution of Australia

Section 109 of the Constitution of Australia 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 jurisdictions is considered persuasive in the others.

Section 109 of the Constitution of Australia provides that:

When a law of a State is inconsistent with a law of the Commonwealth, the latter shall prevail, and the former shall, to the extent of the inconsistency, be invalid.

Section 109, together with section 5 of the Commonwealth of Australia Constitution Act 1900 (which is not part of the Australian Constitution) have been considered to be the foundation for the existence of the judicial review power in Australia. The section provides:

5. This Act, and all laws made by the Parliament of the Commonwealth under the Constitution, shall be binding on the courts, judges, and people of every State and of every part of the Commonwealth, notwithstanding anything in the laws of any State...

"Invalidity of a State law" does not mean that the State law is invalid in the postitivist sense that the State Parliament lacks power to pass it. The State law, though enacted with full procedural validity, merely ceases to have operative force. Hence, in order for s.109 to come into operation at all, there must be a valid State law and a valid Commonwealth law. When s.109 takes effect, the State law yields to the Commonwealth law, but remains a valid law of the Parliament which enacted it. The practical significance of this will become apparent if, at some later date, the overriding Commonwealth law ceases to operate. This effect applies also to laws passed by a state (ie., while it was a colony) prior to the establishment of the Australian Constitution as well as those passed by a state after the Commonwealth had passed a relevant law.

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.

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