Australia High Court Rejects Mount Pleasant Coal Expansion Appeal Over Overseas Emissions

A coal approval turns on 860 million tonnes of overseas emissions

Australia's High Court has dismissed MACH Energy's appeal over the Mount Pleasant coal mine expansion by a 3–2 majority, leaving its approval invalid because New South Wales planning authorities failed to properly consider conditions addressing emissions from the coal's use overseas. The project near Muswellbrook would double permitted annual extraction from 10.5 million to 21 million tonnes and extend mining until December 2048.

The central figure is 860 million tonnes of projected Scope 3 emissions, principally from burning exported coal. Those emissions represent about 98% of the project's estimated greenhouse gas footprint. The court found that acknowledging them was not enough: the Independent Planning Commission also had to consider whether conditions could minimise them to the greatest extent practicable.

The decision, described as the High Court's first substantive climate change ruling, dismissed the company's appeal with costs. It preserves the result secured by the Denman Aberdeen Muswellbrook Scone Healthy Environment Group, known as DAMSHEG, in the NSW Court of Appeal in July 2025.

The ruling does not itself order the existing mine to close or ban all fossil fuel expansions. Although the original consent permitted extraction only until 22 December 2026, MACH Energy says a separate NSW government permit issued in August allows another six years of operation. The larger expansion remains a separate approval issue.

That distinction matters for workers, residents and investors. The judgment blocks reliance on the challenged expansion approval, while leaving questions about a revised application, operating permissions and future emissions conditions to further legal and planning processes.

What the commission approved in 2022

The Independent Planning Commission's 2022 statement of reasons, dated 6 September, approved the Mount Pleasant Optimisation Project subject to conditions. Its panel comprised chair Alice Clark, Chris Fell and Terry Bailey.

The document describes an established open cut mine about three kilometres northwest of Muswellbrook and five kilometres south of Aberdeen. MACH Energy bought the mine in 2016 and began mining in 2018. The existing consent, first granted on 22 December 1999, had undergone five modifications by June 2022.

The proposed expansion would deepen part of the mining area and permit approximately 444 million tonnes of run of mine coal over the project's life, including an estimated 406 million tonnes beyond the previous approval. Run of mine coal is the material extracted before processing, so that figure should not be treated as the quantity of finished coal exported.

The commission concluded that a conditional approval was in the public interest and consistent with the Environmental Planning and Assessment Act 1979. It also expressly recognised that, without conditions, the predicted negative impacts would warrant refusal. The legal dispute therefore concerned whether the conditions process addressed the full emissions footprint, rather than whether the commission had considered environmental effects at all.

Why counting emissions was not enough

Clause 2.20 of the NSW Resources State Environmental Planning Policy requires consideration of whether greenhouse gas emissions are minimised to the greatest extent practicable. It also requires an assessment that includes downstream emissions, taking account of applicable state and national policies, programs and guidelines.

The commission stated that it had considered all emissions, including Scope 3, and that overseas emissions would be accounted for in consumer countries. The High Court majority found that this did not discharge the separate obligation to consider conditions for minimising those emissions.

Justice James Edelman explained why the focus on emissions from operating the mine was insufficient:

By focusing only upon 2% of the project's emissions, the Commission failed in its reasons to consider whether conditions should be imposed to ensure that greenhouse gas emissions are minimised to the greatest extent practicable.

Justice Gordon likewise distinguished international emissions accounting from the commission's planning duties:

The impact of greenhouse gas emissions is the same, regardless of how they are categorised.

The ruling requires consideration of conditions. It does not establish a universal requirement to offset every tonne of exported emissions, nor does it prescribe the conditions that a future approval must contain.

What the emissions figures actually measure

Scope 1 emissions arise directly from mining activities, including methane releases and fuel use. Scope 2 emissions arise from producing electricity purchased by the operation. Scope 3 covers other emissions associated with the product, principally the coal's eventual combustion in this case.

The commission's lifetime estimates were 13.9 million tonnes of carbon dioxide equivalent for Scope 1, 2.17 million for Scope 2 and 860 million for Scope 3. Carbon dioxide equivalent expresses the warming effect of different greenhouse gases using a common measure.

Adding those categories gives 876.07 million tonnes. Scope 3 accounts for approximately 98.2% of that total, while Scope 1 and Scope 2 together account for 16.07 million tonnes, or about 1.8%. These figures explain why stronger controls on mine operations alone could leave most of the project's estimated climate footprint outside the conditions considered.

Reports differ on the combustion figure. One describes more than 870 million tonnes as emissions caused by burning the coal. The commission's table instead assigns 860 million tonnes to Scope 3 and 876.07 million tonnes to all three categories combined. Those are different measures and should not be used interchangeably.

Overseas combustion is generally recorded in the importing country's greenhouse gas inventory rather than Australia's. The court's finding concerns a different question: what NSW authorities must consider when approving the extraction project. Inventory allocation does not settle that planning obligation.

The operating controls left the biggest category unresolved

The 2022 consent included an Air Quality and Greenhouse Gas Management Plan intended to reduce direct emissions intensity below the level proposed in the application. Emissions intensity measures pollution per unit of coal produced, rather than the mine's total emissions.

The conditions sought a Scope 1 intensity of 0.028 tonnes of carbon dioxide equivalent per tonne of run of mine coal, calculated using a five year rolling average, as soon as reasonably feasible and no later than 2034. Reviews of abatement technology were required within 12 months of the plan's approval and every three years thereafter.

Other requirements addressed energy efficiency, feasible emissions reduction technology for new mobile diesel equipment, and renewable or carbon neutral electricity where reasonable and feasible. The commission allowed offsets for emissions exceeding prescribed reduction levels, but rejected requiring offsets for the entire project footprint.

These measures were directed primarily at the mine's own activities and purchased electricity. An intensity target can reduce emissions per tonne without necessarily reducing total emissions when production increases. Here, permitted extraction was to double, while overseas combustion remained the dominant category.

Australia's federal Safeguard Mechanism also operates separately from these planning duties. Its standard annual baseline decline is 4.9% for covered facilities, with credits available for compliance. That framework addresses facility emissions, not the overseas combustion of exported coal.

How the dispute reached the High Court

The case developed through several approvals and court proceedings, with the residents' group arguing that climate harm from exported coal would also be felt in the Hunter region. The main milestones are:

• 22 December 1999: The original Mount Pleasant development consent was granted.
• 2016 and 2018: MACH Energy acquired the mine and subsequently began mining.
• 6 September 2022: The Independent Planning Commission approved the optimisation project with conditions.
• 4 April 2024: Lock the Gate published concerns about a separate Mount Pleasant modification proposal while the larger expansion faced legal challenges.
• July 2025: The NSW Court of Appeal ruled against the expansion approval and sent the matter back to the Land and Environment Court.
• August 2026: According to MACH Energy, a separate NSW government permit allowed another six years of operation.
• October 2026: The High Court dismissed MACH Energy's appeal by three votes to two.

Anita O'Hart, the principal lawyer who represented the residents' group, described the decision as a confirmation that planning authorities must address the causal connection between a project and its emissions:

The High Court has confirmed that planning authorities cannot ignore the chain of causation from a project's emissions.

DAMSHEG president Wendy Wales, a retired science teacher, connected the legal outcome to the group's argument about local exposure to global climate harm:

We cannot dig up coal, ship it overseas, watch it drive climate change, and then pretend the consequences have nothing to do with us and won't be felt by us.

Jobs and local impacts remain part of the dispute

The commission's approval was based on a broader assessment of economic and environmental effects. It projected an average of 447 direct and indirect full time equivalent jobs in the Muswellbrook and Upper Hunter local government areas, 643 in the wider Hunter Valley region and 444 elsewhere in NSW. Those geographic categories should not automatically be added together because the local areas sit within the wider region.

The commission also recorded approximately A$1.4 billion in incremental direct value added benefits to NSW, measured in net present value. That calculation discounts future benefits into present terms. The commission qualified the weight it gave the economic assessment because of coal price uncertainty, discount rates and disputed methods for assigning greenhouse gas costs.

Biodiversity measures involved disturbing up to 475 hectares of native vegetation while relinquishing permission to clear 485 hectares elsewhere. The commission required biodiversity credits and a management plan, concluding that residual impacts could be offset.

Public submissions were predominantly supportive: of 988 written submissions, 72% supported the application, 26% objected and 2% provided comments. Economic and social issues accounted for 67% of submission topics, air quality and emissions for 17%, and climate change for 9%.

Those findings help explain the original approval, but they did not remove the obligation to consider emissions conditions. The court's decision concerns the legality of that process, not a fresh judicial calculation of the project's economic benefits.

A separate modification route complicates the picture

Questions about Mount Pleasant's future extend beyond the optimisation approval. Lock the Gate's coal modification analysis, published on 4 April 2024, identified a separate Modification 7 proposal while the larger project faced federal and NSW legal challenges.

The advocacy organisation said that modification would add 57 million tonnes of coal, bringing its stated total to 142 million tonnes. It listed 192 million tonnes for the contested larger expansion. Those totals differ from the commission's 444 million tonnes of run of mine coal, and the publications do not establish a common measurement basis that would allow them to be reconciled confidently.

Lock the Gate identified nine of at least 17 proposed NSW coal expansions as using modification applications, which are determined within the Planning Department rather than through the Independent Planning Commission. It argued that this reduced independent scrutiny and public participation. Four projects with disclosed emissions estimates totalled approximately 324 million tonnes of lifetime carbon dioxide equivalent.

The organisation's report predates the High Court decision by more than two years. It does not establish that Modification 7 is the same permission MACH Energy says it received in August 2026. What it does show is that multiple approval routes were already being pursued, making the legal status of the large expansion distinct from continued operation under other permissions.

Why gas producers are watching a NSW coal case

The ruling's direct legal effect rests on NSW planning law. University of Melbourne lecturer Liz Hicks said that limits its automatic reach into other states:

The decision turns on NSW law, so its direct effect on other states is limited, but courts and decision-makers across the country will take note.

Western Australia Treasurer Rita Saffioti said her government was seeking urgent legal advice. Woodside's A$30 billion Browse proposal, designed to produce more than 11 million tonnes of gas annually, remains under consideration by state and federal environmental bodies. WA Premier Roger Cook said the ruling would not spell the project's end.

Chamber of Minerals and Energy WA chief executive Aaron Morey warned that restricting Australian projects could shift investment to countries with lower environmental standards. Independent oil and gas consultant Jeanette Roberts said challenges after approvals had been granted increased investor uncertainty. Conservation Council of WA executive director Matt Roberts argued that exported emissions should form part of environmental assessments.

The Australian Conservation Foundation has brought its own climate case concerning Browse. Astrid Puentes Riano, the UN special rapporteur on the right to a clean, healthy and sustainable environment, is expected to participate as a friend of the court, providing a perspective without becoming a principal party.

The attention is unsurprising given Australia's share of about one fifth of global liquefied natural gas trade. However, the judgment does not automatically invalidate Browse or the separate approval extending Woodside's Burrup Peninsula facilities until 2070.

What remains undecided

MACH Energy said it was disappointed but would review the judgment and pursue available options for the operation's continuity. NSW Premier Chris Minns said the company was still pursuing an application through the commission. No next hearing date or deadline for a revised determination has been identified.

Federal Industry Minister Tim Ayres described the ruling as confined to NSW legislation and the planning authority's process. University of Melbourne law professor Jacqueline Peel said requiring mines to address Scope 3 emissions could nevertheless change their economics:

If you start requiring mines to actually deal with and be accountable for their scope 3 emissions and have to do something to minimise those, then it makes the coal mine a much different economic prospect than it would be if you can just deal with scope 3 emissions as someone else's problem.

Recent approvals could face further judicial review, but no finding has been made that they are all invalid. Whether a challenge succeeds will depend on the applicable law, the authority's reasoning and the conditions it considered.

The ruling also follows a 2024 UK Supreme Court decision requiring assessment of emissions from the eventual use of an oil project's output, and the International Court of Justice's July 2025 advisory opinion addressing state obligations concerning fossil fuel production. Those decisions provide an international context, rather than replacing the NSW provision at issue here.

Political descriptions of the judgment range from a climate victory to accusations of judicial overreach. Its immediate requirement is more specific: NSW authorities cannot treat overseas emissions accounting as a substitute for considering how approval conditions might minimise the emissions of the project before them.

Key Points

• The High Court dismissed MACH Energy's appeal with costs by a 3–2 majority.
• The challenged expansion would double permitted annual extraction to 21 million tonnes and extend mining until December 2048.
• The commission estimated 860 million tonnes of Scope 3 emissions, about 98% of the project's total footprint.
• NSW planning authorities must consider conditions addressing those emissions, even when coal is burned overseas.
• MACH Energy says a separate August permit allows six more years of operation, so the ruling is not an immediate mine closure order.
• The decision directly interprets NSW law; its effect on other states and other approvals requires separate assessment.