What it does
The Coastal Waters (Northern Territory Powers) Act 1980 is a short but constitutionally significant statute whose core function is to extend the legislative competence of the Northern Territory Legislative Assembly to the coastal waters adjacent to the Territory. It does so without altering the Territory's land boundaries or disturbing the Commonwealth's overarching responsibility for Australia's territorial sea under international law.
Section 3 supplies the two central definitions. "Coastal waters of the Territory" is given a bifurcated meaning: paragraph (a) captures the part or parts of the territorial sea of Australia that lie within the "adjacent area" previously described in Schedule 2 to the repealed Petroleum (Submerged Lands) Act 1967; paragraph (b) adds any sea on the landward side of the territorial sea that is also within that adjacent area but outside the existing limits of the Territory. The "adjacent area" itself is frozen by reference to the boundary description that existed immediately before the commencement of this Act. This deliberate use of a repealed statute's schedule ensures geographic certainty while linking the new regime to the pre-existing offshore petroleum settlement.
Section 4 then fixes the spatial extent of both the territorial sea and the coastal waters. Subsection (1) provides that the limits of the territorial sea are those "existing from time to time" ascertained consistently with the Seas and Submerged Lands Act 1973, any instruments made under it, and any relevant international boundary agreements. Subsection (2) contains an important safeguard: if Australia ever declares a territorial sea wider than 3 nautical miles, the coastal waters of the Territory for the purposes of this Act do not include the additional expanse. The practical effect is to cap the automatic extension of Territory legislative power at the historic 3-nautical-mile limit even as the Commonwealth's sovereignty expands.