A group of families - including one from Fiji - are appealing against the decision to reject their attempt to sue the European Union over its climate targets.
The 'People's Climate Case', as it has been dubbed, was thrown out in April by the General Court of the European Union, which said individuals didn't have the right to challenge the bloc's environmental plans.
But the families, who said climate change imperils their homes and livelihoods, are appealing that decision to the European Court of Justice, the 28-nation bloc's highest court.
Backed by a group called the Climate Action Network, they want the EU to do more to limit climate change caused by greenhouse gas emissions and to mitigate its effects.
Experts have said the lower court ruling could have a major impact on future climate change litigation.