MACH Energy v Denman Aberdeen Muswellbrook Scone Healthy Environment Group - High Court of Australia
(Filed 2025, HCA, ongoing)
Johnson Legal with counsel and Wendy Wales and Tony Lonergan of DAMSHEG outside the High Court of Australia in Canberra (from left: Anita O’Hart, Matthias Thompson, Naomi Sharp SC, Stephanie Patterson, Wendy Wales, Tony Lonergan, Asha Keaney, Elaine Johnson, Tracey Lynch, Georgia Zhang, Natalie Jakacic and Rachael Chick). Credit: Zoe Lonergan
Johnson Legal is defending the landmark decision of the NSW Court of Appeal in Denman Aberdeen Muswellbrook Scone Healthy Environment Group Inc v MACH Energy Australia Pty Ltd [2025] NSWCA 163, where the Court of Appeal overturned approval of the Mount Pleasant Coal Mine expansion on climate grounds. We are acting for local Hunter Valley community group, Denman Aberdeen Muswellbrook Scone Healthy Environment Group (DAMSHEG).
The NSW Court of Appeal found that due to the direct causal link between the mining of coal in the Upper Hunter and climate impacts experienced by local communities, local climate impacts like bushfires, floods, heatwaves, drought and associated costs are a mandatory relevant consideration when assessing the impacts of the coalmine expansion in the locality.
MACH Energy filed an application for Special Leave to appeal the decision to the High Court of Australia. The application was granted on 4 December 2025.
Principal Lawyer Anita O’Hart of Johnson Legal is representing DAMSHEG in the High Court, defending the unanimous decision of the three-judge bench in the NSW Court of Appeal. Naomi Sharp SC, Matthias Thompson and Stephanie Patterson of counsel are appearing for DAMSHEG in these proceedings.
The matter was heard by the High Court of Australia in Canberra on 13 May 2026.
The High Court is the apex court in the Australian jurisdiction. This appeal will be the first time that the High Court of Australia will conduct a hearing on the issue of climate change.
Submissions were filed by MACH Energy, DAMSHEG and four institutions seeking to be heard as amici curiae (“friends of the court”).
The Court granted leave for each of the amici curiae to be heard. The Union of Concerned Scientists and Melbourne Climate Futures were heard on their written submissions and orally at the hearing on 13 May 2026. The Sabin Centre for Climate Change Law and the Centre for Climate Engagement were heard on their written submissions.
05 February 2026: Written submissions and chronology (MACH Energy - Appellant)
05 March 2026: Written submissions (DAMSHEG - First Respondent)
19 March 2026: Written submissions (The Union of Concerned Scientists - amicus curiae)
19 March 2026: Written submissions (Sabin Centre for Climate Change Law, Colombia Law School and Centre for Climate Engagement, University of Cambridge - amici curiae)
19 March 2026: Written submissions (Melbourne Climate Futures, University of Melbourne - amicus curiae)
26 March 2026: Reply submissions (MACH Energy - Appellant)
30 March 2026: Written submissions on amici curiae (DAMSHEG - First Respondent)
13 May 2026: Hearing transcript (High Court of Australia)
13 May 2026: Outline of oral argument (MACH Energy - Appellant)
13 May 2026: Outline of oral argument (DAMSHEG - First Respondent)
13 May 2026: Outline of oral argument (Melbourne Climate Futures - amicus curiae)
13 May 2026: Outline of oral argument (The Union of Concerned Scientists - amicus curiae)
The audio-visual recording of the hearing is available here
