Section 51(xxxi) of the Australian Constitution

Section 51(xxxi) of the Australian Constitution grants the Commonwealth Parliament the power to make laws with respect to: "The acquisition of property on just terms from any State or person for any purpose in respect of which the Parliament has power to make laws."

This section is a crucial limitation on the Commonwealth's power to acquire property. It has two key components:

• Acquisition of Property: The Commonwealth’s action must constitute an “acquisition” of property. This does not simply mean the Commonwealth benefits; the previous owner must suffer a deprivation or loss of property rights. The definition of "property" is broad and includes both tangible and intangible assets.

• Just Terms: The acquisition must be on "just terms." This phrase requires the Commonwealth to provide fair and adequate compensation for the property acquired. What constitutes "just terms" is a matter for the courts to determine, taking into account factors such as market value, special value to the owner, and the circumstances of the acquisition. Disputes over just terms are often litigated.

The purpose limitation in section 51(xxxi) is also significant. The acquisition must be for a purpose within the Commonwealth Parliament's legislative power. This means the purpose of the acquisition must be linked to another head of power granted to the Commonwealth in the Constitution, such as defense, trade, or corporations.

Section 51(xxxi) operates as a protection for individuals and states against the potential abuse of power by the Commonwealth. It ensures that if the Commonwealth needs to acquire property, it must do so fairly and for legitimate purposes. This provision has been the subject of considerable judicial interpretation and remains a significant aspect of Australian constitutional law.