The United Nations General Assembly has endorsed the International Court of Justice's landmark advisory opinion on states' climate obligations, with 141 countries voting in favour, 8 against and 28 abstaining at a session in New York.

The resolution (A/80/L.65) recognises and endorses the ICJ opinion issued last year, which found that countries can be held legally responsible for their greenhouse gas emissions. Vanuatu proposed the resolution, and more than 60 countries co-sponsored it, including many Pacific nations already threatened by sea-level rise.

New Zealand voted in favour despite declining to co-sponsor. Ministry of Foreign Affairs officials refused to disclose the country's position ahead of the vote. New Zealand had co-sponsored the original 2023 resolution that requested the ICJ opinion on states' climate change obligations.

Eight states voted against the resolution: Belarus, Iran, Israel, Liberia, Russia, Saudi Arabia, the United States and Yemen.

The due diligence standard

Eliza Prestidge-Oldfield, a researcher at the Environmental Law Initiative, told RNZ before the vote that one of the crucial findings of the ICJ opinion was that countries must exercise strict "due diligence" in lowering their emissions.

"[It's] saying you actually have to try really, really hard. You can't just say, 'Oh yeah, we'll get to that later,'" she said.

A UN resolution endorsing the opinion "would be a really strong statement that we expect all countries to be doing the best they can on climate change", she added.

Legal weight regardless of the vote

The ICJ opinion remains the "authoritative legal statement" on states' obligations even without the resolution, Prestidge-Oldfield said. It will carry weight in both international and domestic legal decisions on climate change issues, regardless of which states endorsed it.

The resolution's practical function is political. "In lay terms ... it's the political seal of recognition of the [ICJ] decision," she said.

For practitioners, the combination of the advisory opinion and its endorsement by a supermajority of UN member states strengthens the evidentiary and normative footing of climate litigation in domestic courts and before international bodies. States voting in favour, including New Zealand, now face a formally recognised statement of obligations that litigants can cite when challenging insufficient emissions-reduction measures.

Commentary split on significance

Victoria University climate science professor James Renwick welcomed the resolution's passage but said international action to actually lower emissions was "completely absent" so far.

"It's incredible that it takes a ruling from the International Court of Justice and a vote in the UN to push countries towards what they willingly signed up to 10 years ago under the Paris Agreement," he said. "Fossil fuel companies still hold sway and we are all paying the price with increasing extreme weather events."

He urged governments to now "do what you said you would".

Nathan Cooper, associate law professor at the University of Waikato, said New Zealand's support for the resolution was welcome but argued the government had abandoned the country's previous role as a regional leader on climate action.

"Now, with the resolution adopted, it is time for our government to revisit recent climate-related decisions - including reversing the ban on off-shore oil and gas exploration - that the [ICJ] opinion identifies as a breach of state obligations and an 'internationally wrongful act'," Cooper said.

The vote closes the procedural loop that began in 2023, when the General Assembly asked the ICJ to clarify states' climate obligations. The opinion now stands endorsed by the Assembly, with the eight opposing states recorded against it.