Vanuatu has urged the International Court of Justice (ICJ) to find polluting nations have acted unlawfully by contributing to climate change, in a landmark case that could change future climate talks.

But Australia, which also addressed the court at The Hague, in the Netherlands, on Monday said obligations for nations to prevent climate change largely did not extend beyond major international climate treaties including the Paris Agreement.

The ICJ, nicknamed “the World Court”, began hearings into the responsibilities of nations to prevent climate change — and the consequences for them if they fail.

Vanuatu, which led the global campaign for the ICJ to hear the case, opened with an impassioned call for the court to find nations must cease greenhouse gas emissions and offer reparations.

The Pacific Island nation’s special envoy on climate change, Ralph Regenvanu, said “a handful of readily identifiable states” had been the source of “the vast majority of historic and current greenhouse gas emissions”.

“We look to the court for recognition that the conduct which has already caused immense harm to my people and so many others is unlawful, that it must cease and that its consequences must be repaired.”

Vanuatu’s delegation argued the court should consider the broad set of international laws on human rights and the environment in its opinion.

Mr Regenvanu said the recent climate talks in Azerbaijan — which he criticised for failing to deliver cuts to greenhouse gas emissions — had shown “first-hand, once again, the failure of the [COP] process”.

“There is an urgent need for a collective response to climate change grounded not in political convenience but in international law,” Mr Regenvanu said.

Australia emphasises climate agreements

Australia’s lawyers said the judges should interpret any other international laws “harmoniously” with climate change treaties including the Paris Agreement and the UN Framework Convention on Climate Change (UNFCCC).

Australian solicitor-general Stephen Donaghue argued these agreements were the “primary source of states’ obligations under international law in respect of climate change”.

Australian National University professor in international law Donald Rothwell told the ABC that Australia had taken a more conservative stance than Vanuatu on the obligations of states on climate change under international law.

He said Australia had also diverged from Vanuatu’s position in relation to COP talks.

“[Australia] is basically saying to the court, we have a process … that process is a dynamic one,” Professor Rothwell said.

“It changes from time to time and there needs to be a recognition that within that process, there will be eventually a resolution of some of the issues that are before the court in this advisory opinion.”

Australia’s stance drew rebuke from environmental advocates.

Greenpeace Australia Pacific general counsel Katrina Bullock said Australia’s argument had directly contradicted Vanuatu’s submissions and ignored decades of developments in international human rights law.

“And compliance with those treaties is necessary, but it is certainly not sufficient to safeguard human rights and the environment.”

Save the Children Vanuatu youth ambassador Vepaiamele Trief said she was disappointed with Australia’s position in the ICJ case.

“As a close Pacific neighbour, Australia has a duty to stand with Pacific Island nations and support what they’re striving for,” she said.

“To go to the International Court of Justice and just completely go against what we’re striving for is very sad to see.”

The ABC has sought comment from the Australian government but has not received a response.

Nearly 100 countries will speak over two weeks of hearings — including the United States and China this week.

Experts say the court’s findings could bolster the cases of nations taking legal action against big polluters failing to reduce emissions.

Pacific countries also hope the findings could strengthen their hand in future climate change negotiations like COP.