NZ climate policies could be harder to justify in court than days ago, says law professor

Tuesday, 26 May 2026

The Government’s climate policies could be more exposed to legal challenges as a result of its decision to fall in behind a United Nations vote endorsing an advisory opinion from the International Court of Justice, a law professor says.

Nathan Cooper, associate professor of law at the University of Waikato, said there might now be a stronger argument that New Zealand was obliged to achieve the commitment it made under the Paris Agreement to cut its net emissions by 2030.

Until now, the Treasury has advised that its pledge to reduce net carbon emissions to 50% below gross 2005 levels by 2030 — a so-called Nationally Determined Contribution (NDC) — was not legally binding. That advice could have implications for whether the Government may need to spend billions of dollars buying overseas carbon offsets to achieve the commitment.

Cooper said the ICJ opinion and UN vote also opened up the possibility that the Government’s decision to lift the ban on new offshore oil and gas exploration permits could be judged an “internationally wrongful act”.

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The UN General Assembly last week endorsed, by 141 votes to eight, an advisory opinion issued by the ICJ in July that climate change treaties imposed binding obligations on countries and that they could be required to pay compensation to “injured states” for failing to meet them.

Parties to the Paris Agreement had an obligation to “pursue measures which are capable of achieving the objectives set out in their successive Nationally Determined Contributions”, it said.

The advisory opinion also said states have a “duty to prevent significant harm to the environment by acting with due diligence and to use all means at their disposal to prevent activities carried out within their jurisdiction or control from causing significant harm to the climate system”.

New Zealand did not co-sponsor the UN resolution endorsing the ICJ opinion and Canterbury University political science professor Bronwyn Hayward asserted that the Government’s vote in favour had been “very reluctant”.

The vote took place in the wake of the Government retrospectively preventing people from suing businesses over greenhouse gas emissions after lobbying by companies including Fonterra and Z Energy.

A spokesperson for the Ministry of Foreign Affairs and Trade told The Post the UN vote did “not create new legal obligations, nor does it alter states’ existing legal obligations under international law”.

Professor Cooper said that was “technically correct”, given it was the ICJ advisory opinion itself — rather than the vote — that could have that effect.

The advisory opinion was also not a “ruling” by the ICJ, as such, he noted.

“It is not legally binding in the sense that it wasn’t made in relation to an active question in front of the court in litigation. It was, as the name suggests, a piece of advice on how it might answer questions if they came up in front of the court.”

But he said national courts were already using the ICJ’s advisory opinion to “inform their own opinions and their own judgments”.

“It's already starting to be folded into climate litigation in different countries.”

He said they were more likely to adopt its viewpoint now that had been endorsed by the UN’s General Assembly, including by the Government here.

“The General Assembly has basically just said, ‘we all acknowledge that this opinion is the state of the art. It is the authoritative statement of international law on state obligations to climate change, we all accept it, we all go along with it’.”

“A few months ago, it would have been unlikely a New Zealand court would have ignored the advisory opinion if relevant questions were in front of it. Today it’s almost unthinkable, because New Zealand has said, 'Yes, okay, this is authoritative.”

There was a stronger argument to say New Zealand was obliged to achieve its NDCs than there was before the ICJ’s advice, and now that argument was “stronger still”, he said.

The developments also made it “that much more difficult” to square the lifting of the oil and gas ban with the ICJ stance, Cooper said.

“If I was preparing legal advice for the Government, then I would be certainly less confident today than I was a couple days ago.”

Victoria University climate and geography professor James Renwick said it was “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”.

Hayward said the ICJ’s opinion was starting to shape national and international obligations and “showed the power of domestic voters and of small island negotiators”.