Quick questions on Section 109 and Commonwealth-state inconsistency: VCE Legal Studies

Section 109 of the Constitution of the Commonwealth of Australia provides:

The High Court has identified three forms of inconsistency.

The state law is invalid "to the extent of the inconsistency". This is a partial, not total, invalidation: only the inconsistent portion is struck down. If the inconsistent Commonwealth law is later repealed, the state law revives.

Amalgamated Society of Engineers v Adelaide Steamship Co Ltd (1920) 28 CLR 129 (the Engineers Case). The Engineers Case reset constitutional interpretation. The High Court rejected the doctrines of reserved state powers and implied intergovernmental immunities, holding that Commonwealth laws made under s 51 powers applied to state-owned enterprises. This established the modern approach: Commonwealth heads of power are interpreted on their natural meaning and prevail under s 109 in areas of concurrent power.

The Australian Constitution distributes legislative power between the Commonwealth and the states. The states have plenary legislative power; the Commonwealth has enumerated powers under s 51 (and a few other heads). Most s 51 powers are concurrent (both can legislate). Section 109 is the device that resolves the conflict where both have legislated.

The state law and Commonwealth law impose directly contradictory obligations. Example: a state law that requires conduct the Commonwealth law prohibits.

The Commonwealth law manifests an intention to cover the field exhaustively. Any state law in that field is inconsistent. (Ex parte McLean (1930) 43 CLR 472.)

The High Court struck down the Marriage Equality (Same Sex) Act 2013 (ACT) on the ground that the Marriage Act 1961 (Cth) (as it then stood) was intended to cover the field of marriage. The ACT Act could not operate concurrently. (The Commonwealth subsequently amended the Marriage Act 1961 (Cth) to recognise same-sex marriage in 2017.)