MACH Energy Australia Pty Ltd v Denman Aberdeen Muswellbrook Scone Healthy Environment Group Inc & Anor

In December 2022, the Denman Aberdeen Muswellbrook Scone Health Environment Group Inc (DAMSHEG) commenced judicial review proceedings in the NSW Land and Environment Court challenging the decision of the Independent Planning Commission (IPC) to grant development consent to the expansion of MACH Energy’s Mount Pleasant coal mine in the Upper Hunter Valley of NSW.

The project would extend the mine’s operations to 2048 and generate substantial greenhouse gas emissions, including emissions from the eventual combustion of exported coal.

The challenge was dismissed in the NSW Land and Environment Court, but upheld in the NSW Court of Appeal which declared the development consent invalid because the IPC had failed to consider a mandatory consideration under s 4.15(1)(b) of the Environmental Planning and Assessment Act 1979 (NSW) (EPA Act). That consideration was the local environmental consequences of climate change in the Hunter Valley arising from the project’s contribution to global emissions.

MACH Energy obtained special leave to appeal to the High Court.

The High Court appeal turns principally on s 4.15(1)(b) of the EPA Act, which requires a consent authority to consider “the significant likely impacts of that development, including environmental impacts on both the natural and built environments, and social and economic impacts in the locality”.

The question is essentially what counts as a “likely impact” of a development, and how far the causal chain can extend for the purpose of that provision.

The case is the first to ask the High Court to consider the extent to which climate change impacts be considered when assessing fossil fuel projects under NSW planning law.
The High Court heard the appeal on 13 May 2026.

Melbourne Climate Futures (MCF) is a University of Melbourne initiative dedicated to the advancement of multi-disciplinary climate change research. MCF’s key research areas include climate law, policy and governance, including climate litigation, with particular attention to serving our growing Indo-Pacific region.

An amicus curiae (Latin for “friend to the court”) assists the Court on points of law. Amicus are generally not parties to the proceedings, do not file pleadings or lead evidence, and may not lodge an appeal.

In April 2026, MCF was granted leave to appear as amicus curiae in the High Court proceedings alongside The Union of Concerned Scientists, The Centre for Climate Engagement and The Sabin Center for Climate Change Law.

MCF made a number of arguments to assist the High Court. In summary:

1. Section 4.15(1)(b) requires a two-stage inquiry. The consent authority must first identify the “likely impacts” of the development – including impacts that are caused by or flow from it – and then consider those impacts in deciding whether to approve the development.
2. “Likely impacts” is not geographically confined. MCF argued that the reference to environmental impacts “in the locality” does not restrict the broader category of “likely impacts”. The provision can encompass both local and non-local environmental impacts where they are relevant to the development.
3. Climate impacts are part of the causal chain. Emissions from the mine will impact the climate system and the resulting changes to the climate system will in turn affect other components of the natural and built environment, including through extreme weather, bushfires and heavy rainfall. MCF argued that s 4.15(1)(b) requires the decision-maker to consider that causal chain.

MCF relied on international and comparative climate litigation and climate attribution science to argue that MACH Energy’s claim that an individual project’s emissions cannot be causally connected to local climate impacts is inconsistent with the state of scientific knowledge and the developing jurisprudence.

MCF’s full written submissions are available here.

The hearing in the High Court of Australia took place on 13 May 2026. MCF delivered short oral submissions on the key points above.

Judgment is currently reserved.

Documents in the case can be viewed here.

Melbourne Climate Futures is represented by Equity Generation Lawyers.

Melbourne Climate Futures’ counsel are Zelie Heger SC, Zoe Bush and Rohan Nanthakumar.