The High Court of Australia will today hand down its ruling in the nation’s first climate change case to reach the country’s highest court, with implications for a major coal mine expansion near Muswellbrook and for planning decisions across the state.
The case, MACH Energy Australia Pty Ltd v Denman Aberdeen Muswellbrook Scone Healthy Environment Group Inc, was originally brought by a grassroots Hunter Valley community group challenging the approval of the expansion of the Mount Pleasant open-cut coal mine. The court will decide whether planning authorities are legally required to consider the local climate impacts of a mine’s downstream emissions, known as Scope 3 emissions, before granting approval.
The NSW Court of Appeal ruled unanimously in July 2025 that the approval was unlawful, finding the Independent Planning Commission had failed to meet a mandatory obligation under the Environmental Planning and Assessment Act to consider the specific local climate impacts of the mine’s emissions. MACH Energy was granted special leave to appeal in December 2025 and asked the High Court to overturn the ruling at a hearing on 13 May 2026. Judgment has been reserved since.
MACH Energy sought to double the mine’s output to 21 million tonnes a year and extend its life to 2048, which DAMSHEG claim would generate an additional 870 million tonnes of carbon dioxide, 98 per cent of it from coal burned overseas.
The ruling will have direct implications for more than 17 coal proposals in the NSW planning pipeline, as well as climate litigation nationally and internationally.
