High Court rejects Mount Pleasant coal mine expansion approval over emissions assessment

Australia’s High Court dismissed MACH Energy’s appeal on 7 October 2026, leaving invalid the 2022 approval for an expansion of its Mount Pleasant coal mine near Muswellbrook in New South Wales’ Hunter Valley. The court found that state planners had failed to consider whether conditions could minimise greenhouse gas emissions from the project, including emissions produced when exported coal is burned overseas. The ruling affects the proposed expansion; a separate approval allows the existing mine to operate until 2032.

Why the Mount Pleasant expansion approval failed

The case concerned a decision by the New South Wales Independent Planning Commission. A majority of three High Court judges found that the commission had not considered imposing conditions to minimise the project’s greenhouse gas emissions to the greatest extent practicable. That requirement extended to Scope 3 emissions: those associated with the eventual use of the exported coal. Two judges dissented on whether the commission had met this obligation.

The distinction matters because the emissions generated by burning the coal abroad account for almost all of the project’s estimated climate impact. The High Court record put Scope 3 emissions at 98% of total greenhouse gas emissions and said the challenged approval imposed no conditions to minimise them. The ruling requires the planning authority to consider possible conditions; it does not specify what those conditions should be or decide whether the expansion should ultimately proceed.

The ABC reported that MACH Energy’s proposal involved extracting 444 million tonnes of coal and projected more than 870 million tonnes of carbon dioxide-equivalent emissions from its combustion overseas. Those are estimates for the proposed project, not emissions already produced. Scope 3 emissions from coal burned abroad are also outside Australia’s domestic greenhouse gas inventory, the ABC reported. The court’s finding concerns how those emissions were handled in the state approval process.

What happens to the mine and its workers

The expansion approval had already been overturned by the New South Wales Court of Appeal in July 2025 after a challenge brought by the Denman Aberdeen Muswellbrook Scone Healthy Environment Group. MACH Energy appealed that outcome to the High Court. The dismissal of its appeal leaves the expansion without the challenged 2022 approval, while the existing mine’s separate permission remains in force.

MACH Energy told the ABC it would review the decision and pursue available options for Mount Pleasant’s long-term continuity. It said it would work with regulators, governments and local communities on the practical implications. The New South Wales government likewise said it would examine the full judgment and engage with the company. Neither statement establishes a timetable or outcome for a fresh decision on the expansion.

Could the ruling affect other coal approvals?

The ruling may influence how New South Wales planning authorities assess future fossil fuel projects, but it does not automatically overturn other approvals. The state government said the recently approved Hunter Valley Operations project included detailed consideration of Scope 3 emissions and conditions to minimise them. Greens state MP Sue Higginson, however, argued that the High Court judgment could create legal difficulty for that extension. Her assessment concerns a separate project and is not a court ruling on its approval.

The possible reach beyond New South Wales is also uncertain. University of Melbourne lecturer Liz Hicks told the ABC that the decision turns on state law, limiting its direct effect elsewhere, although courts and decision-makers around Australia will take note. Federal Environment Minister Murray Watt told the Guardian that he had not yet reviewed the full judgment and said it did not automatically transfer to Commonwealth decisions or legislation.

The community group that brought the case sees the decision as recognition that emissions from exported coal can still affect communities near the mine. Its president, Wendy Wales, told the ABC that this was the group’s position throughout the dispute. Opponents of the ruling have drawn a different policy lesson: Liberal leader Angus Taylor and Nationals leader Matt Canavan called it a threat to Australia’s reputation as a reliable energy exporter and urged changes to New South Wales law, the Guardian reported.

For now, the practical result is narrow but consequential: the proposed expansion lacks its 2022 approval, while Mount Pleasant may continue operating under its separate permission. Any renewed expansion decision will depend on the process New South Wales follows after reviewing the judgment, including how it addresses possible emissions-minimisation conditions. The available statements do not establish when that process will begin or whether a new approval will be granted.