09 October 2026
6 min read
#Planning, Environment & Sustainability
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This week, the High Court of Australia, comprising Justices Gageler, Gordon, Edelman, Jagot and Beech-Jones, delivered judgment in the matter of Mach Energy Australia Pty Ltd v Denman Aberdeen Muswellbrook Scone Healthy Environment Group Inc & Anor [2026] HCA 35. The case has attracted significant media attention, painting its impact in various lights. But what does the case really mean for applicants and consultants?
The Mount Pleasant coal mine, owned by Mach Energy Australia Pty Ltd (MACH), is an open cut mine in the Hunter Valley, New South Wales (NSW).
The ‘state significant development’ application made by MACH to the NSW Department of Planning and Environment (the Department), had included an environmental impact statement (EIS), which included ‘potential impacts of the Project’ and ‘potential impacts on the Project’. The EIS addressed greenhouse gas emissions (GHG), covering Scope 1, 2 and 3 emissions – but mitigation measures offered only in terms of the Scope 1 and Scope 2 emissions. It is relevant to note at this juncture, that under the NSW regime applicable at the time, the onus was on MACH to provide a full description of mitigation measures intended to mitigate any adverse effects of the development in its EIS.
In terms of the Scope 3 emissions, the EIS expressed that ‘a significant majority’ of these would occur overseas, such that they would not count towards Australia’s emissions for the purposes of the Paris Agreement, and that they would be addressed and regulated by the expected export countries.
What followed was the Department recommended conditions to minimise Scope 1 and 2 emissions but did not recommend conditions in relation to Scope 3 emissions.
The Independent Planning Commission of NSW (the Commission), following an objections hearing, approved MACH’s application to extend the life of the mine by 22 years, and expand its operations, subject to conditions. The Commission’s conditions addressed Scope 1 and 2 emissions, but included none which addressed Scope 3 emissions.
Denman Aberdeen Muswellbrook Scone Healthy Environment Group Inc (the Environment Group), applied for judicial review of the Commissions’ decision, which was dismissed by the Land and Environment Court of NSW (which found inference in the Commission’s reasons as a whole, that it had exercised discretion not to attach conditions directed to Scope 3 emissions, and that the Commission did not need to identify ‘specific impacts’, because matters that were considered – were ‘largely impacts of climate change generally’). That dismissal was overturned by the NSW Court of Appeal.
The NSW Court of Appeal found that the Commission had not complied with section 4.15(1)(b) of the Act (in that it did not engage with “the impacts of the proposed development on the locality of the development. A causal enquiry as to the impacts on the locality was required”). The NSW Court of Appeal remitted the matter back to the Land and Environment Court for consideration under Part 3, Division 3 of the Land and Environment Court Act 1979.
Application for leave to appeal the NSW Court of Appeal’s decision was granted by the High Court. The appeal largely turned on two very specific NSW provisions, namely:
“Before granting consent for development for the purposes of mining, petroleum production or extractive industry, the consent authority must consider whether or not the consent should be issued subject to conditions aimed at ensuring that the development is undertaken in an environmentally responsible manner, including conditions to ensure the following:……(c) that greenhouse gas emissions are minimised to the greatest extent practicable”.
In terms of (1) above, the High Court found that a consent authority, operating in accordance with section 4.15(1)(b) of the Act must firstly identify what the ‘likely impacts’ of the proposed development are (noting that no geographical limits are set in section 4.15(1)(b) of the Act). Having done so, the consent authority must ‘take into consideration’ those likely impacts. All five Justices concluded that the Court of Appeal had erred in its interpretation of section 4.15(1)(b) and found in favour of MACH with respect to this issue.
In terms of (2) above, with separate reasons, Justices Gordon, Elderman and Beech-Jones found that the Commission had failed to consider whether conditions should be imposed to minimise (to the greatest extent practicable), Scope 3 emissions. Conditions regarding Scope 1 and Scope 2 emissions had been considered and imposed (accounting for 2% of the project’s emissions), but conditions regarding Scope 3 emissions had not been considered. Rather, the Scope 3 emissions (accounting for 98% of the total emissions), were said to be occurring overseas – where they were to be regulated and addressed via other means (such as the Paris Agreement). It was the failure by the Commission to consider whether to impose conditions going to the Scope 3 emissions (to make up the ‘all GHG emissions’ consideration) that was the issue here (cf. Mullaley Gas and Pipeline Accord Inc v Santos NSW (Eastern) Pty Ltd (2021) 252 LGERA 221). Once this was found by the High Court, it determined that this error was material and a jurisdictional error.
This determination arose out of a judicial review context – concerning very specific provisions in NSW legislation. Accordingly, it does not follow that the findings in this appeal, will automatically have far reaching implications across the country. The High Court was not considering the merits of the mine, nor was it the function of the High Court, “the Court of Appeal or the Land and Environment Court (in this case) to assess the environmental effects of any of the CHG emissions involved in or arising from MACH’s mining and related activities, or to address the merits or otherwise of the Commission’s decision to grant the consent” (paragraph 264). The decision here focused on whether the consent was impacted by jurisdictional error.
Any finding of jurisdictional error, should serve as a reminder to all assessing authorities, that their duties and obligations need to be properly discharged in accordance with the instruments that establish their operating parameters. This case is no different.
Finally, applicants and their consultants who input materials into the system of development assessment, need to pay particular attention to this case. At its heart – one view of this case, is that it could have been avoided (in the form it took), had the application materials addressed what conditions may have been imposed to have addressed not just the Scope 1 and Scope 2 emissions identified, but also the significant extent of Scope 3 emissions. Had the application materials addressed this as was required by the statutory framework, the Commission would then have had its basis to have properly discharged its functions.
The take home - getting applications right, has never been more important.
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Disclaimer
The information in this article is of a general nature and is not intended to address the circumstances of any particular individual or entity. Although we endeavour to provide accurate and timely information, we do not guarantee that the information in this article is accurate at the date it is received or that it will continue to be accurate in the future.
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