Australia's highest court has upheld a ruling which blocked the expansion of Australian producer Mach Energy's 10.5mn t/yr Mount Pleasant thermal coal mine in New South Wales (NSW) in a landmark climate decision that could curb future coal mine approvals.
The High Court of Australia today dismissed Mach Energy's appeal against a July 2025 NSW Court of Appeal ruling which found the state's Independent Planning Commission (IPC) had failed to properly consider indirect greenhouse gas (GHG) emissions when it approved Mount Pleasant's expansion in September 2022. The proposal sought to extend Mount Pleasant's operations from 2026 to 2048 and raise its annual ROM production limit to 21mn t/yr.
The proposed Mount Pleasant expansion will need to be reassessed by NSW authorities following this latest decision. The case against Mach Energy was lodged by community group the Denman, Aberdeen, Muswellbrook and Scone Health Environment Group, represented by Johnson Legal.
The NSW court in 2025 determined that the IPC's approval of Mount Pleasant was invalid because the planning authority failed to fulfill its legal obligation to consider whether to impose conditions to minimise GHG emissions, including scope 3 emissions, to the greatest extent practicable. Mach Energy appealed the decision in May.
The High Court upheld the NSW court's determination, finding that the IPC had imposed conditions relating to the project's scope 1 and 2 emissions, but failed to do the same for scope 3 emissions. Scope 3 emissions accounted for 98pc of the project's estimated emissions.
The High Court ruling suggests NSW planning authorities will need to demonstrate they have considered imposing conditions to manage scope 3 emissions to the greatest extent practicable before issuing approvals. This could mean additional hurdles for coal mine approvals, where scope 3 emissions are often a significant issue.
Mach Energy said it was disappointed with the High Court ruling and would actively pursue all available options to ensure long-term continuity at Mount Pleasant. The decision does not affect a separate approval granted to Mount Pleasant in August, which raised its approved extraction rate to 12.5mn t/yr and extended its operations from 2026 to 2032.
The ruling comes a week after the IPC approved a 19-year extension to the nearby Hunter Valley Operations (HVO) complex after finding the project's social and economic benefits outweighed its climate impacts. Scope 3 emissions account for 98pc of HVO's estimated emissions.
The Mount Pleasant ruling comes at a time of rising climate litigation risks following a 2025 judgement from the International Court of Justice (ICJ), which found that countries have binding legal obligations to cut emissions, and could be found legally responsible if they did not regulate emissions caused by "private actors" in their jurisdictions.
The NSW state government said in March it would stop issuing permits for greenfield thermal coal developments under its NSW Coal Industry 2026-50 framework but would continue to assess extensions of existing coal mines.

