On 13 May 2026, the High Court of Australia will hear the nation’s first ever climate change case to reach our highest court— a landmark moment that will set a binding national precedent on whether Australian planning authorities are legally required to consider the local climate impacts of fossil fuel project approvals.
The case, MACH Energy Australia Pty Ltd v Denman Aberdeen Muswellbrook Scone Healthy Environment Group Inc (DAMS HEG), was brought by a grassroots Hunter Valley community group challenging the approval of a major expansion of the Mount Pleasant open-cut coal mine near Muswellbrook. The NSW Court of Appeal ruled unanimously in July 2025 that the mine’s approval was unlawful — finding that planning authorities are legally required to consider the specific local climate impacts of a project’s downstream emissions. MACH Energy is asking the High Court to overturn that ruling.
The case arrived at an extraordinary moment. Just 12 hours before the NSW Court of Appeal’s ruling, the International Court of Justice in The Hague delivered its own landmark advisory opinion, finding that fossil fuel-exporting nations bear legal responsibility under international law for the climate harm their exports cause. Australia had argued to the ICJ that it bore no such responsibility for emissions from its coal and gas exports. The ICJ rejected that argument.
Four of the world’s leading climate law and science institutions have been granted leave to intervene in the High Court in support of DAMS HEG — from the Universities of Cambridge, Columbia and Melbourne, and the Union of Concerned Scientists. The case is being watched internationally as a test of whether domestic law can hold fossil fuel producers accountable for the local consequences of dangerous climate change.
The case directly affects 18-plus coal proposals in the NSW planning pipeline, and other fossil fuel developments under consideration across Australia. It will provide a foundation for other major climate cases including the Pabai Torres Strait appeal, the North West Shelf challenge, and future climate litigation across Australia and internationally.
Wendy Wales , President, DAMS HEG
Wendy Wales is a retired science teacher and the president of the Denman Aberdeen Muswellbrook Scone Healthy Environment Group — the community group that brought this case. She and her partner Tony Lonergan run a farm in the Upper Hunter Valley, surrounded by open-cut coal mines. She has driven this case through three court levels over four years.
“Our communities are enduring increasingly terrifying climate disasters, and nature is deteriorating before our very eyes. Yet our governments are continuing to throw fuel on the fire by approving massive new projects and expansions like MACH Energy’s Mount Pleasant Optimisation Project. We have felt the catastrophic impacts of droughts, bushfires, floods and a myriad of other tragic events. The short term economic benefits can not be given priority over the exponentially increasing long term consequences”.
Tony Lonergan , Treasurer, DAMS HEG
Tony Lonergan is a retired science teacher and farmer whose family has worked land in the Upper Hunter Valley for generations. His property sits adjacent to the Mount Pleasant mine, and he has joined his wife Wendy Wales and DAMS HEG through this legal journey.
“What could be more important than protecting our unique natural heritage and biodiversity, or ensuring we can live safely in Muswellbrook and the Upper Hunter for generations to come? The continuation of coal mining in NSW prioritises the private interests of a few over a safe climate and the future of our children and grandchildren. Our planning laws are clearly not climate ready if projects as harmful as the Mount Pleasant Optimisation Project are allowed to proceed. Addressing global heating means cutting our greenhouse gas emissions, and fast. Political parties have to face reality. Do you want to address this existential problem or not? Stop pretending.”
Elaine Johnson , Director, Johnson Legal (can not do interviews before hearing)
Elaine Johnson is the founder and director of Johnson Legal, the firm representing DAMS HEG in the High Court proceedings. She has supported her clients through the Court of Appeal proceedings, and now the High Court.
“Continued fossil fuel production is driving climate harms here at home, and Australia is still one of the largest exporters of coal in the world. We look forward to supporting our clients in their defence of the NSW Court of Appeal’s decision overturning the Mount Pleasant Coal Mine expansion.
“The NSW Court of Appeal’s decision was truly groundbreaking, and is already changing how proposals for new and expanded fossil fuel projects are assessed in NSW. The High Court will now determine whether that decision holds at law on appeal.”
Professor Nicole Rogers, Professor of Climate Law, Bond University
Professor Rogers has particular expertise in climate litigation, climate activism and the law, and interdisciplinary climate studies. She is author of two monographs on the legal ramifications of the climate crisis and a co-author of the 2026 Edward Elgar publication Re-imagining Environmental Law . She has published widely on the transformative potential of climate litigation in reshaping legal and policy frameworks.
“Australia’s apex court hearing its first climate change case is a watershed moment in the history of Australian law. Courts around the world — from The Hague to London to Canberra — are being asked the same fundamental questions: can legal systems keep pace with the climate crisis and to what extent are decision makers who continue to approve fossil fuel projects accountable for climate impacts? The Mount Pleasant case is Australia’s latest contribution to that global conversation, and the High Court’s answer will be studied by others well beyond the Upper Hunter Valley.”
“In light of the recent findings of the International Court of Justice, this case and others highlight the growing legal and economic risks for anyone seeking to continue approving fossil fuel projects without considering the real-world climate consequences. Australia is positioning itself as a prime target for future climate litigation if its federal and state governments fail to heed these risks.”
Emeritus Professor Mark Howden AC, ANU Institute for Climate, Energy and Disaster Solutions; Vice Chair, Intergovernmental Panel on Climate Change (IPCC)
Emeritus Professor Howden has worked on climate variability, climate change and climate impacts for over 36 years. He is a Vice Chair of Working Group II of the IPCC — the group responsible for assessing climate impacts, adaptation and vulnerability — and helped develop both the national and international greenhouse gas inventories that underpin the Paris Agreement. His core expertise covers climate science, climate impacts on agriculture and food security, ecosystems, water and energy systems.
“The science on this is unambiguous. Every tonne of carbon dioxide added to the atmosphere contributes to global warming — and that warming is already measurably increasing the frequency and severity of extreme heat, drought, flood and fire events across south-eastern Australia and globally. This is not a projection about the future. It is a description of what is happening now, documented across decades of observation and confirmed by arguably the most comprehensive global scientific assessment process in history.”
“Drawing quantitative linkages between individual greenhouse gas emitters and particularised harms is now feasible, making science no longer an obstacle to the justiciability of climate liability claims. The science linking human activity to observed and future climate changes is clear and unequivocal. The question before the High Court is whether Australian law is prepared to recognise it.”
BACKGROUND
· The Mount Pleasant open-cut coal mine sits 3km upwind and northwest of Muswellbrook in the Upper Hunter Valley, NSW. It is owned by MACH Energy Australia Pty Ltd, a subsidiary of Indonesia’s Salim Group. MACH Energy sought to double the mine’s output to 21 million tonnes per year and extend its life to 2048 — generating an additional 870 million tonnes of CO₂, 98% of it as Scope 3 emissions from coal burned overseas.
· The NSW Court of Appeal ruled unanimously on 24 July 2025 that the Independent Planning Commission had failed a mandatory obligation under s.4.15(1)(b) of the Environmental Planning and Assessment Act 1979 to consider the specific local climate impacts of the mine’s emissions. MACH Energy was granted special leave to appeal on 4 December 2025.
· The ICJ Advisory Opinion on climate change obligations of states was handed down on 23 July 2025 — the day before the NSW Court of Appeal ruling — finding that fossil fuel production, export licensing and subsidies can constitute internationally wrongful acts.
· Five institutions have been granted leave to intervene in the High Court in support of DAMS HEG: Melbourne Law School Climate Futures (Prof. Jacquie Peel), Oxford Faculty of Law (Harj Narulla), Cambridge Centre for Climate Engagement, Sabin Centre for Climate Change Law (Columbia University), and the Union of Concerned Scientists (Dr Christopher Callahan).
· DAMS HEG is represented by Johnson Legal. Lead barrister at the High Court hearing is Naomi Sharp SC. The hearing is scheduled for 13 May 2026 in Canberra.