Cwealth of Aus Ex parte- Wardens of SW Mineral Field

The Commonwealth of Australia sought a writ of prohibition against the Wardens of the South-West Mineral Field, Western Australia. The dispute concerned the validity of certain regulations made by the Governor-in-Council of Western Australia under the *Mining Act 1895* (WA). The Commonwealth contended that these regulations were invalid as they purported to regulate mining on land which had been reserved for the purposes of the Commonwealth.

The primary legal issue before McHugh J was whether the *Mining Act 1895* (WA) and the regulations made thereunder were valid and effective in relation to land within Western Australia that had been lawfully appropriated by the Commonwealth for its purposes. Specifically, the court had to determine if the State of Western Australia retained the power to legislate with respect to mining on such Commonwealth land, or if such legislation was rendered inoperative by reason of the Commonwealth's constitutional powers.

McHugh J reasoned that the Commonwealth, by virtue of its constitutional power to acquire land for public purposes, could exclude the operation of State laws within that land. His Honour applied the principle of paramountcy, which dictates that where a valid Commonwealth law is inconsistent with a State law, the Commonwealth law will prevail to the extent of the inconsistency. In this instance, the appropriation of land by the Commonwealth for its purposes was held to be inconsistent with the State's power to regulate mining on that land, thereby rendering the State regulations inoperative. The court found that the State could not legislate in a manner that would interfere with the Commonwealth's use and enjoyment of its acquired land.