On 7 October 2026 the High Court handed down its first climate change decision, MACH Energy Australia Pty Ltd v Denman Aberdeen Muswellbrook Scone Healthy Environment Group Inc [2026] HCA 35. It will be read for what it says about coal and emissions. For anyone who deals with regulators, the more lasting lesson is about decision-making. A decision-maker who is required to consider a matter must be shown to have considered it, and a gap in its reasons can be fatal.
The background
In 2022 the Independent Planning Commission of NSW approved a 22-year extension of the Mount Pleasant coal mine in the Hunter Valley, to 2048. The extension would allow a further 406 million tonnes of coal to be extracted. A community group, Denman Aberdeen Muswellbrook Scone Healthy Environment Group Inc, challenged the approval by judicial review. It lost at first instance and won in the Court of Appeal. The mine operator then appealed to the High Court.
Where a decision-maker must consider a matter, the Court looks to the written reasons to see whether it did. Silence on a major issue can lead a court to find the consideration never happened.
What the High Court decided
By a 3:2 majority, the High Court dismissed the appeal. The approval stays invalid, but for a different reason than the Court of Appeal gave. Gordon, Edelman and Beech-Jones JJ held that the Commission had failed to comply with a planning policy that required it to consider whether to impose conditions to minimise greenhouse gas emissions "to the greatest extent practicable". Gageler CJ and Jagot J would have allowed the appeal.
The facts mattered. About 98 per cent of the project's emissions were "scope 3" emissions, released when the coal is burned, mostly overseas. The Commission's reasons dealt carefully with conditions for the remaining 2 per cent. They did not mention conditions for the 98 per cent. Gordon J said that, given how aware the Commission was of the impacts of climate change, it would be "extremely curious" for it to have focused only on conditions for 2 per cent of the emissions. The Court found nothing in the reasons from which it could infer that the Commission had considered the question.
Three points for regulatory disputes
- Reasons are the evidence. Where a decision-maker must consider a matter, the Court looks to the written reasons to see whether it did. Silence on a major issue can lead a court to find the consideration never happened.
- The onus is not heavy. The challenger had to show the decision-maker failed to consider the matter. Once the reasons showed no consideration, that was enough.
- Materiality is a low bar. The error was material because there was a "realistic possibility" the decision could have been different without it. A challenger does not have to prove the outcome would have changed.
What this means for businesses
These principles apply well beyond planning. Licences, approvals, enforcement decisions and investigations all rest on statutory considerations. If you hold an approval, check whether the reasons behind it show that every required matter was addressed. If you are challenging a decision, read the reasons for what they leave out as well as what they say.
How GopherWood Lawyers Can Help
GopherWood Lawyers acts in regulatory disputes and investigations, including challenges to regulatory decisions. Get in touch for a free 30-minute consultation.
This article reflects the judgment as published on 7 October 2026. The Court notes that its copy of the reasons is subject to formal revision.