High Court says the Mount Pleasant expansion skipped Scope 3 conditions

The High Court of Australia on Wednesday dismissed an appeal by MACH Energy and held, by majority, that the Independent Planning Commission of New South Wales failed to consider imposing conditions to minimise Scope 3 greenhouse gas emissions from the Mount Pleasant coal expansion. The case is Muswellbrook Scone Healthy Environment Group, reported as [2026] HCA 35. The existing approval that lets the mine operate until 2032 is a separate decision and is not set aside.

Mount Pleasant is an open-cut mine in the Hunter Valley. MACH Energy applied to extend its life by 22 years and to expand the pit. After public hearings the Commission approved the application. Scope 3 emissions, the gases from burning the coal after it is sold, were 98 percent of the project's predicted total. The Commission imposed no condition aimed at those emissions. Denman Aberdeen Muswellbrook Scone Healthy Environment Group, known as DAMSHEG, sought judicial review.

The legal question was narrow. Section 4.15 of the Environmental Planning and Assessment Act 1979 requires a consent authority to consider the matters the law lists, including instruments that apply to the land. Clause 2.20(1)(c) of the State Environmental Planning Policy (Resources and Energy) requires consideration of conditions that would minimise, to the greatest extent practicable, the greenhouse gas emissions of the development. The High Court held unanimously that the Commission had complied with section 4.15(1)(b), the general duty to consider impacts. By majority it held that the Commission had not considered conditions on Scope 3 emissions, as clause 2.20 and section 4.15(1)(a)(i) required. The Court said its summary is not a substitute for the reasons.

The New South Wales government answered the same day. The natural resources minister said Mount Pleasant has a separate approval to keep operating until 2032, and that Wednesday's ruling does not change that. The ruling concerns how the expansion was assessed and approved in 2022, under the previous government. It does not say an expansion can never be approved. The minister pointed to the state's coal policy for 2026 to 2050, and to the later approval of Hunter Valley Operations, which did include a detailed Scope 3 assessment and conditions. MACH has said it will keep pursuing options. The government said it will look at the judgment before the next decision.

The 98 percent figure is the fact that makes the case travel. If almost all of the counted emissions sit in the coal after it leaves the mine, a consent that minimises only the diesel and the methane on site has addressed the small share. The Court's majority did not order a tonne limit. It said the Commission had to consider whether a condition could cut Scope 3 emissions as far as practicable, and that this consideration did not happen. A future commission can still approve an expansion. It has to show the consideration the 2022 decision skipped.

For the workforce the operable line is the minister's. The mine's approval to 2032 stands. Rosters tied to that approval are not cancelled by [2026] HCA 35. What is open is the 22-year extension. MACH can go back. The commission that hears it will have the High Court's map of the duty. Buyers of Hunter coal will read the same map. A cargo's Scope 3 count is now a matter a New South Wales consent authority must consider, on this mine and, by the same clauses, on the next one.