The High Court has dismissed MACH Energy’s appeal over the expansion of its Mount Pleasant coal mine near Muswellbrook, in the Hunter Valley, leaving the approval for that expansion invalid.
The judgment was handed down on Wednesday 7 October. It ends a case that a local residents’ group had fought for more than four years.
The ruling was split 3-2, Guardian Australia reported, with three of the five judges in the majority, according to the ABC. Two of the five judges dissented.
It is the first time the High Court has dealt with a case on climate grounds, according to Guardian Australia and legal experts cited by the ABC.
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What the Court Decided
The case was about what the NSW Independent Planning Commission had to take into account before it approved the expansion. The question before the judges was whether the commission had considered everything it was legally required to consider.
The majority found that the commission was required to consider imposing conditions to minimise the project’s greenhouse gas emissions. That included scope 3 emissions, which in this case are the emissions from the mine’s coal when it is burnt overseas. The majority found the commission did not consider those conditions, Guardian Australia and the ABC reported.
Because the commission did not consider those conditions, the approval for the expansion does not stand.
The expansion would have almost doubled the output of the Mount Pleasant coal mine. It would also have kept the mine running until 2048, both outlets reported.
How the Case Reached the High Court
The challenge was brought by the Denman Aberdeen Muswellbrook Scone Healthy Environment Group, a residents’ group from the area around the mine.
In 2025, the NSW Court of Appeal ruled against the approval. MACH, which had lost at that stage, then appealed to the High Court and asked it to overturn the decision. Wednesday’s decision dismisses that appeal, so the Court of Appeal’s ruling against the approval remains in place.
The Reactions
The residents’ group, the miner and the coal industry each responded to the ruling.
Wendy Wales, president of the group that brought the case, welcomed the decision. “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,” she said, as reported by Guardian Australia.
The group’s principal lawyer, Anita O’Hart, spoke about what the ruling means for planning authorities. “The High Court has confirmed that planning authorities cannot ignore the chain of causation from a project’s emissions,” she said, according to the ABC.
MACH Energy said it accepts the decision and will review it. “We advanced this appeal to obtain clarity on important questions regarding the scope of mandatory considerations in environmental decision-making,” the company said in a statement reported by the ABC.
For the mining industry, Tania Constable of the Minerals Council of Australia described the ruling as “a further blow to Australia’s prospects of meeting continued demand for our high-quality coal from global customers”, Guardian Australia reported.
Her comment on global demand comes in the same month that G7 leaders agreed to free 100 million barrels of oil over four months from their reserves.
What the Ruling Changes
The ruling deals with the approval for the expansion, the part of the project that was before the court. It does not shut the existing mine.
A separate state approval, granted in August, allows the current operation to keep running for about six more years, Guardian Australia reported. The ABC reported that approval as running until the end of 2032.
The existing operation and the expansion are now on different footings. The current mine is covered by the August approval, while the approval for the expansion, which would have run the mine to 2048, is invalid.
Outside New South Wales, its reach is narrower. A University of Melbourne lecturer cited by the ABC said the ruling turns on NSW law, so its direct effect in other states is limited.
For now, MACH Energy is reviewing the judgment, which ends a case the residents’ group had pursued for more than four years.
Sources: ABC News, “High Court rules in favour of climate group in Hunter Valley coalmine case”, 7 October 2026 (https://www.abc.net.au/news/2026-10-07/mount-pleasant-coal-mine-high-court-ruling/107233650); Guardian Australia, “Hunter Valley community group wins landmark high court climate change case over Mount Pleasant coalmine”, 7 October 2026 (https://www.theguardian.com/environment/2026/oct/07/mount-pleasant-coalmine-case-high-court-climate-change-hunter-valley)
Photo: DaHuzyBru, CC BY-SA 4.0, via Wikimedia Commons.
The High Court of Australia building in Canberra, January 2026. Pictured for context; no part of this frame was taken on the day of the judgment.