Section 51(vi) of the Australian Constitution

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 naval and military defence of the Commonwealth and of the several States, and the control of the forces to execute and maintain the laws of the Commonwealth".

ection 51(vi) and the Australian States

Generally, powers in section 51 of the Australian Constitution 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. Section 114 of the Australian Constitution provides that "a state shall not, without the consent of the Parliament of the Commonwealth, raise or maintain any naval or military force...". As a result, the power in section 51(vi) is generally exclusive to the Commonwealth.

Section 119 of the Australian Constitution compliments section 114 by placing an obligation on the Commonwealth to exercise the power granted in section 51(iv). Section 119 provides that "the Commonwealth shall protect every State against invasion and, on the application of the Executive Government of the State, against domestic violence."

Breadth of Section 51(vi)

The defence power allows the Commonwealth to raise an army and navy. Although aeroplanes 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 World War 1 and World War 2 the power was held to apply very broadly, even to domestic issues. For example, it was used in 1942 to support the Commonwealth taking away income tax powers from the states. This was upheld in the First Income Tax Case. After the war the Commonwealth redesigned the scheme to rely on Section 96 tiered grants, which demonstrates that perhaps the Commonwealth felt the scheme would not be upheld based on the defence power during peace time. (see Constitutional basis of taxation in Australia).

A broad interpretation may continue after the cessation of war. In 1949 the Commonwealth used the defence power to support the Snowy Mountains Hydroelectricity Scheme, as although wartime hostilities had ceased a secure electricity source was needed should Australia be attacked. This creative use of the defence power illustrates that the power is potentially quite broad.

However, the defence power does have limitations. The defence power was one of the powers relied on to support the Communist Party Dissolution Act, which attempted to dissolve the Communist Party of Australia. In the Communist Party Case, the High Court held that the Cold War, or the Korean War, did not justify this use of the defence power.