The High Court found that the state's planning body, the Independent Planning Commission, was obligated to consider how to minimise the greenhouse gas emissions produced from the mine's coal when it is sold and burned abroad, and that it failed to do so.
The expansion would have doubled the mine's output to 21 million tonnes per annum until 2048. The court found that 98% of the projected emissions from the project are scope 3 emissions, which occur outside the direct control of the mine operator.
"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," said Wendy Wales, president of the Denman Aberdeen Muswellbrook Scone Healthy Environment Group (Dams Heg), which brought the original case.
The case, brought by MACH Energy, is the first time Australia's highest court has been asked to consider a case on climate grounds. The community group, led by Ms Wales and her partner Tony Longeran, has pursued the case through the courts for more than four years, starting in the Land and Environment Court, where they were initially unsuccessful, before winning on appeal in the NSW Court of Appeal in 2025.
Advocates say the ruling sets a binding national precedent for fossil fuel projects in New South Wales and potentially across Australia, requiring authorities to factor in the full climate impact of a project's contribution to global emissions and their local consequences.