Australia’s High Court has issued its first-ever decision in a climate case, ruling that planning authorities must consider the complete greenhouse gas footprint of fossil fuel projects — including so-called scope 3 emissions produced when coal or gas is burned by overseas customers. The decision, handed down Wednesday, concerns an attempted expansion of MACH Energy’s Mount Pleasant open-cut coal mine in New South Wales’s Hunter Valley, but its implications extend well beyond a single project.
The Mount Pleasant mine, located near Muswellbrook, was originally approved to operate until December 2026 with an annual output of 10.5 million tonnes of coal. In 2021, MACH Energy sought to extend its life by 22 years and double production to 21 million tonnes per year through to 2048. A local community group, the Denman Aberdeen Muswellbrook Scone Healthy Environment Group, challenged the NSW Independent Planning Commission’s 2022 approval of that expansion, arguing the commission had failed to properly assess how the mine’s emissions — the vast majority of which occur overseas when the coal is burned — would worsen climate change in the Hunter region. The group also contended the commission had breached a NSW planning rule requiring it to consider conditions minimising greenhouse gas emissions, including scope 3 emissions, to the greatest extent practicable.
The community group initially lost in the NSW Land and Environment Court but won unanimously at the Court of Appeal in July 2025, which declared the approval invalid. MACH Energy then appealed to the High Court. In a split decision — three judges to two — the High Court upheld the appeal court’s finding. The majority ruled the planning commission had not done enough to assess scope 3 emissions or how they might be reduced or mitigated, and rejected the argument that overseas emissions are another jurisdiction’s concern. As Justice Michelle Gordon wrote, those emissions cause the same detrimental impact regardless of how they are categorised.
The ruling directly affects 17 other coal proposals currently in NSW’s planning pipeline and could serve as a legal blueprint for climate cases elsewhere in Australia. Decision-makers approving future coal or gas projects in NSW will now be expected to consider imposing conditions — such as requiring developers to purchase carbon offsets — to address scope 3 emissions. Experts note, however, that offsets are not a comprehensive solution, as they allow companies to compensate for emissions without reducing output. The case now returns to the NSW Land and Environment Court, which may suspend the mine’s operation or set conditions that could prove costly for MACH Energy.
The ruling aligns with a broader international trend. Courts in Norway and the United Kingdom have similarly required decision-makers to account for all emissions linked to fossil fuel projects, and the International Court of Justice ruled last year that countries are legally obliged to assess the effects of such projects both domestically and abroad. With Australia co-hosting a pre-COP31 climate summit in the Pacific this week and facing pressure from Pacific leaders over its fossil fuel sector, the High Court’s decision adds legal weight to calls for a more comprehensive accounting of the climate costs of new coal and gas development.