The Queensland government in April denied an environmental licence to Waratah Coal, which is owned by Mr Palmer's company Mineralogy, for a coal project in the Galilee Basin.

The decision was recommended by the Land Court in November last year, which ruled the proposal to extract up to 56 million tonnes of coal a year "risks unacceptable climate change impacts" on the environment and on human rights.

Land Court President Fleur Kingham found that even though the mine was intended for exports, "wherever the coal is burnt the emissions will contribute to environmental harm, including in Queensland".

Indigenous-led activist group Youth Verdict had also opposed the project over its claimed impact on human and cultural rights.

Waratah Coal, starting in December last year, filed two lawsuits in the Brisbane Supreme Court against the Queensland Department of Environment, the Land Court and Ms Kingham as well as multiple climate change activists in an attempt to overturn the licence refusal.

Supreme Court Chief Justice Helen Bowskill on Wednesday granted an application by Waratah Coal to discontinue the last of the appeals and ordered the mining company to pay costs.

Comment has been sought from the Waratah Coal and the activists' legal defence team.

The Department of Environment's licence refusal could still be subject to challenge via an investor-state dispute arbitration brought by Mr Palmer's Singapore-registered company Zeph Investments against the Australian government.

Zeph Investments has claimed damages of $41.3 billion from Australia allegedly breaching its free trade agreements over mineral exploration permits held by Waratah Coal in the Galilee Basin.

The federal Attorney-General's Department has previously labelled the claims "unsubstantiated" and indicated it will "vigorously defend the claim".

Australian Associated Press