The ICJ will hear testimony from nearly 100 countries, including Vanuatu. Photo: ABC News: Doug Dingwall
Vanuatu's special envoy to climate change says their case to the International Court of Justice (ICJ) is based on the argument that those harming the climate are breaking international law.
The case seeks an advisory opinion from the Court on the legal responsibilities of countries in relation to climate change, and dozens of countries are making oral submissions.
Hearings started in The Hague with Vanuatu - the Pacific island nation that initiated the effort to obtain a legal opinion - on Monday morning, Netherlands time.
Ralph Regenvanu told RNZ Morning Report they are not just talking about countries breaking climate law.
Vanuatu-led climate case gives evidence at International Court of Justice
He outlined their argument as: "This conduct - to do emissions which cause harm to the climate system, which harms other countries - is in fact a breach of international law, is unlawful, and the countries who do that should face legal consequences."
He said they are wanting a line in the sand, even though any ruling from the Court will be non-binding.
"We're hoping for a new benchmark in international law which basically says if you pollute with cumulative global greenhouse gas emissions, you cause climate change, then you are in breach of international law," he said.
"I think it will help clarify, for us, the UNFCCC (UN Framework Convention on Climate Change) process negotiations for example."
Regenvanu said COP29 in Baku was frustrating, with high-emitting states still doing fossil fuel production and the development of new oil and coal fields.
He said a ruling from the ICJ, though non-binding, will clearly say that 'international law says you cannot do this'.
"So at least we'll have something, sort of a line in the sand."
Oral submissions to the Court are expected to take two weeks.
Another Pacific climate change activist says at the moment there are no consequences for countries failing to meet their climate goals.
Pacific Community (SPC) director of climate change Coral Pasisi said a strong legal opinion from the ICJ might be able to hold polluting countries accountable for failing to reach their targets.
The court will decide on two questions:
What are the obligations of states under international law to protect the climate and environment from greenhouse gas emissions?
And, what are the legal consequences for states that have caused significant harm to the climate and environment?