A lawyer says a Supreme Court ruling on an iwi leader Mike Smith's climate case may open a new avenue in climate law.
The climate activist, of Ngāpuhi and Ngāti Kahu, will have his full case heard in court after the Supreme Court ruled his case against seven big polluters for their roles in causing climate change could proceed.
Smith is not seeking money and said he wanted a safer world.
Two of the companies, Genesis and Fonterra, said the ruling will delay work on cutting emissions.
Daniel Street from law firm DLA Piper said the ruling would get attention, though Smith still needed to prove his case at a full hearing.
He said this case provided a new avenue for the types of climate change litigation that could be brought.
"Previously, tort law has been closed off to these sorts of claims.
"This particular claim has been one of much interest internationally, so there have been a number of my international colleagues and international NGOs and climate activist groups who've been following this case closely, and I suspect similar arguments being run in numerous cases offshore."
He said this ruling would mean the main issues at the heart of the case would be tested.
"The getting past the strikeout stage means you get that detailed consideration and then if Mr Smith was successful on the main elements of this claim, then you get the question of, well, what is the appropriate relief in a case such as this."
Street said Smith would have to prove "private harm".
"In tort law, it is all about private harm. So the question is, what harm has been caused to Mr Smith and to his land and his property from emissions from the defendants."
Smith raised the issue of coastal erosion and coastal damages, he said, but it would be hard to identify the particular harm to him, "especially when the actions of the defendants in this case, whilst potentially large on a New Zealand scale, are very small in the context of global climate change".
Genesis Energy said in a statement it was "disappointed", and that the case would divert resources from actually cutting emissions by building up renewable energy.
Lawyers for the big emitters had argued in court that damage from climate change affected everyone, and was best tackled by laws and Parliament, not by the courts using common law.