MACH Energy loses High Court bid over Mount Pleasant coal mine expansion in NSW after landmark climate challenge

Australia’s highest court has upheld a first-of-its-kind climate change challenge in a landmark ruling that could have far-reaching consequences for future fossil fuel projects around the country.

The High Court’s decision on Wednesday found planning authorities are required to take into account the impact on local climate change before approving such development.

The test case stemmed from MACH Energy’s move to extend the life of its Mt Pleasant coal mine in NSW by 22 years and nearly double its yearly output.

The State planning commission in 2022 approved the plans before local Hunter Valley residents launched a legal challenge.

The first bid to block the expansion was tossed before the NSW Court of Appeal unanimously ruled the approval unlawful in 2025.

The appeal court found planning authorities are legally required to consider the climate impact of so-called scope 3 emissions -— caused when the coal is eventually burnt, including when exported overseas — on local communities.

MACH Energy took the finding to the High Court, which struck down the appeal on Wednesday morning.

“By majority, the High Court held the (planning) commission had failed to consider imposing conditions to minimise to the greatest extent practicable all greenhouse gas emissions, specifically ‘scope three’ emissions as required (by law),” the court said in a summary.

The Denman Aberdeen Muswellbrook Scone Healthy Environment Group brought the case, led by Hunter resident Wendy Wales and represented by Johnson Legal.

The local leader previously said she hoped the court would uphold the decision and “turn a super tanker around”.

On Wednesday she said the court’s decision acknowledged the risks to Australians posed by climate-influencing activities.

“This ruling acknowledges that many Australian communities have already suffered extreme weather devastation,” she said.

“Now the true and complete long-term costs of export coal on Australians, via the climate impact from burning that coal, must be considered.”