Australia's High Court has delivered a 3-2 ruling that the approval of MACH Energy's Mount Pleasant coalmine expansion in Muswellbrook, NSW, was invalid because the Independent Planning Commission failed to consider how to mitigate scope 3 emissions — the greenhouse gases generated when exported coal is burned overseas. This is the first time Australia's highest court has adjudicated a climate change case, and the ruling creates a binding national precedent for fossil fuel project assessments in New South Wales. The Mount Pleasant expansion would have doubled coal output to 21 million tonnes per annum through 2048, with 98% of projected emissions classified as scope 3. The majority found the IPC was required not merely to acknowledge these emissions but to consider imposing conditions aimed at minimising them to the greatest extent practicable. The court invalidated the approval on different grounds than the earlier NSW Court of Appeal decision, but the practical effect is the same: the expansion cannot proceed under its current approval. The immediate downstream target is obvious. The Hunter Valley Operations coalmine extension — described as the biggest in NSW history — was approved by the IPC just one week ago. NSW Greens MP Sue Higginson noted that HVO's environmental impact statement did not even account for scope 3 emissions. If the legal test established by this ruling is applied consistently, that approval is vulnerable to immediate challenge. The case was brought by retired science teacher Wendy Wales and the Denman Aberdeen Muswellbrook Scone Healthy Environment Group (DAMS HEG), who pursued it through three levels of courts over more than four years. The community group won at the NSW Court of Appeal after losing in the Land and Environment Court, and now prevailed at the High Court after MACH Energy appealed. The persistence is notable: a volunteer community group outlitigated a coal company through Australia's entire judicial hierarchy. The coal industry response reveals the structural tension. MACH Energy said it would "continue to actively pursue all available options" for the mine's continuity, noting a separate modification approved in August extends operations by six years. The Minerals Council of Australia called the decision "a further blow to Australia's prospects of meeting continued demand" and highlighted the absurdity of mines being required to reduce emissions from their export customers. That framing is precisely the point the court rejected — the IPC cannot treat scope 3 emissions as someone else's problem. The ruling's real force is systemic. Australia is the world's second-largest coal exporter. If every NSW coal approval must now demonstrate that scope 3 emissions have been minimised to the greatest extent practicable, the planning approval pathway for new or expanded coal exports becomes vastly more complex and legally precarious. This does not ban coal mining, but it inserts a binding legal friction point into every future approval that was previously absent. What remains uncertain is the practical meaning of "minimised to the greatest extent practicable." The court established the obligation but did not define its ceiling. Does it mean carbon offsets? Contractual conditions on buyers? Reduced output volumes? The IPC and future courts will have to operationalise a standard that the High Court has declared mandatory but left deliberately open. That ambiguity is where the next decade of litigation will live.
