The Australian government has won an appeal against a ruling that it has a duty of care to protect children from harm caused by climate change.
Last year, eight teenagers and an 87-year-old nun convinced a court that the government had a legal duty to children when assessing fossil fuel projects.
The decision was hailed as a world first, but it has been successfully challenged by the environment minister.
The teenagers could still take the case to Australia's highest court.
"Today's ruling leaves us devastated, but it will not deter us in our flight for climate justice," said 17-year-old Anjali Sharma, in a statement released by their lawyers.
Their case attempted to stop the expansion of the Vickery coal mine in New South Wales, which is estimated to add an extra 170 million tonnes of fossil fuel emissions to the atmosphere.
Three judges in the Federal Court of Australia unanimously sided with Environment Minister Sussan Ley on Tuesday, but their list of reasons differed.
Chief Justice James Allsop said he thought elected officials should decide policy matters, but noted there was "no dispute" in the case that climate change itself caused harm.
Justice Michael Wheelahan said there was an "incoherence" between the law and the minister's obligations to rule that she had a duty of care. Justice Jonathan Beach said there was not "sufficient closeness or directness" between the minister's decision and "any reasonably foreseeable" harm from the mine.
Ms Ley did not immediately comment on the decision.
Another student involved in the case, 15-year-old Izzy Raj-Seppings, said: "Our lawyers will be reviewing the judgment and we may have more to say in the coming weeks."
"While today's judgement did not go our way, there is still much to celebrate. The court accepted that young people will bear the brunt of the impacts of the climate crisis."
Catholic nun Brigid Arthur acted as the teenager's legal guardian in the case. Last year, she told the BBC that they had "every right to be calling people to account".
A report published at the COP26 global climate summit last year ranked Australia last among 60 countries for policy responses to the climate crisis.
The country is the world's second-largest coal exporter and Prime Minister Scott Morrison has said the industry will operate there for "decades to come".
Australia has committed to achieving net zero carbon emissions by 2050, but it has faced criticism over its 2030 targets.