Section 51(vi) of the Constitution of Australia

Section 51(vi) of the Australian Constitution, commonly called the defence power, is a subsection of Section 51 of the Australian Constitution that gives the Commonwealth Parliament the right to legislate with respect to the defence of Australia and the control of the defence forces. The High Court has adopted a different approach to the interpretation of the defence power, which emphasises the purpose of the legislation, primarily the defence of Australia, rather than the subject matter.

The defence power is set out in section 51 of the Constitution as follows:

51 The Parliament shall, subject to this Constitution, have power to make laws for the peace, order, and good government of the Commonwealth with respect to:

Generally the Commonwealth powers in section 51 can also be legislated on by the states, although Commonwealth law will prevail in cases of inconsistency. However, the defence power must be read in conjunction with other parts of the Australian Constitution — namely,

114. A State shall not, without the consent of the Parliament of the Commonwealth, raise or maintain any naval or military force, or impose any tax on property of any kind belonging to the Commonwealth, nor shall the Commonwealth impose any tax on property of any kind belonging to a State.

and

This effectively makes the defence power exclusive to the Commonwealth.

The defence power allows the Commonwealth to raise an army and navy. Although air forces did not exist in 1901, "military defence" has been considered broad enough to include an air force. What other laws the defence power will support has been held by the High Court of Australia to vary based on external circumstances.

During the two World Wars, the power was held to apply very broadly, even to domestic issues. In October 1914 the Australian Parliament enacted the War Precautions Act 1914, which gave the Governor-General a broad power to "make regulations for securing the public safety and the defence of the Commonwealth". These powers were retrospectively amended in 1916 to specifically include price controls. A determination was published in the Gazette fixing the maximum price for 4 pounds of bread to be sold in Melbourne at 6 ¹⁄₂ pence. The High Court considered the validity of this legislation in Farey v Burvett, with the majority, Griffith CJ, Barton, Isaacs, Higgins & Powers JJ, holding that the defence powers in sub-section 51(vi) of the Constitution was sufficient during the war for the Commonwealth to fix the maximum price for bread.

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