Retired teachers win High Court fight over coal mine expansion

What the High Court decided

Australia's High Court dismissed MACH Energy's appeal by a three to two majority on 7 October 2026, upholding the NSW Court of Appeal's unanimous ruling that the Independent Planning Commission broke the law when it approved the Mount Pleasant coal mine expansion.^[1] The Court found the IPC failed its mandatory duty under section 4.15(1)(b) of the Environmental Planning and Assessment Act 1979 (NSW) by not considering the likely impacts of Scope 3 greenhouse gas emissions on the environment in the locality.^[1]

Scope 3 emissions represented 98 per cent of the project's total greenhouse gas emissions, yet the IPC imposed no conditions to minimise them.^[2] Scope 3 emissions are those produced when the coal is burned by overseas customers, distinct from the Scope 1 and 2 emissions generated at the mine site itself.

Anita O'Hart, principal lawyer at Johnson Legal, which represented the community group, said the ruling locked in a new standard for every planning body in the state. O'Hart said the High Court confirmed that planning authorities cannot ignore the chain of causation from a project's emissions through to real, local climate harm, and that the Independent Planning Commission was required to consider those impacts, an obligation now binding across the NSW planning system.^[4]

What the expansion would have involved

The proposed 22-year optimisation project would have extended the mine's operating life to 22 December 2048, extracted an additional 406 million tonnes of coal, and doubled annual production from 10.5 million tonnes to 21 million tonnes per year.^[1] Mount Pleasant is an open cut operation near Muswellbrook in the Upper Hunter Valley, owned by MACH Energy Australia Pty Ltd, a subsidiary of the Salim Group.

The mine's existing consent was due to expire on 22 December 2026. Without a fresh and lawful approval process, the expansion cannot proceed.

What happens to the expansion now

The matter does not automatically void the project. The NSW Court of Appeal, when it ruled against MACH Energy on 24 July 2025, remitted the case to the Land and Environment Court to consider whether the consent could be conditionally validated rather than declared void outright.^[3] The High Court's dismissal of the appeal leaves that remittal in place, so the case remains remitted to the Land and Environment Court for its consideration of whether the consent could be conditionally validated rather than declared void outright.

The Land and Environment Court may suspend or vary the consent subject to specified conditions, including conditions that address the Scope 3 emissions gap the IPC failed to fill.^[1] Clause 2.20 of the State Environmental Planning Policy (Resources and Energy) 2021 already obliges the IPC to consider imposing conditions to minimise greenhouse gas emissions to the greatest extent practicable.

What the ruling means for other NSW fossil fuel approvals

Section 4.15(1)(b) of the Environmental Planning and Assessment Act 1979 (NSW) is now confirmed to require consent authorities to take into account the likely climate impacts of downstream emissions on the local environment, not only the emissions produced at the project site.^[3] That obligation applies to every consent authority in NSW, not only the IPC.

The decision is expected to reshape the approval pathway for proposed fossil fuel projects in the state. Any application that fails to model and address Scope 3 emissions as a local environmental impact now carries a legal vulnerability the High Court has placed beyond doubt.

Mining industry representatives warned before the judgment that a loss for MACH Energy would generate widespread approval uncertainty and threaten jobs in the Hunter Valley, one of Australia's largest coal-producing regions. Neither MACH Energy nor any industry body had issued a public statement by the time of publication.

Reactions: community group and legal team

Wendy Wales, president of the Denman Aberdeen Muswellbrook Scone Healthy Environment Group, said the Court had confirmed what her community had argued since December 2022. Wales said: "Today the High Court has said what we have always known: we cannot dig up coal, ship it overseas, watch it drive climate change, and then pretend the consequences have nothing to do with us and won't be felt by us. The droughts, the bushfires, the floods, are directly connected to greenhouse gases, and massive fossil fuel projects like the Mount Pleasant optimisation simply add fuel to the fire."^[4]

MACH Energy said it was "disappointed with the outcome" but accepted the court's decision. "We will continue to actively pursue all available options to ensure the long-term continuity of the Mount Pleasant operation," the company said in a statement. [AFP]

The community group's judicial review, lodged in the Land and Environment Court in December 2022, challenged the IPC's approval on the grounds that it failed to consider Scope 3 emissions under both section 4.15(1)(b) and clause 2.20 of the Resources SEPP 2021.^[1] The Land and Environment Court dismissed that challenge in August 2024. The Court of Appeal unanimously overturned the decision in July 2025, and the High Court has now upheld the appeal ruling by a three to two majority.

The matter next returns before the Land and Environment Court, where the court will determine the question of conditional validation and whether the consent can be conditionally validated rather than declared void outright.