Auckland Council has a "legal obligation" to decarbonise transport in the city, says Jenny Cooper QC.

Presenting to the council's planning committee last week, the president of Lawyers for Climate Action NZ said the council was legally obliged under the Local Government Act "to promote an environmental wellbeing for present and future generations."

The Auckland based commercial litigator said climate change law also explicitly provides for all public decision-makers to take the 2050 zero-carbon goal into account in their decisions.

"When you are doing something that is so clearly critical to the ability to achieve that goal, for example with the regional land transport plan, that is clearly a material consideration for the council, that if it fails to take that into account will be unlawful."

She said the council operates under the NZ Bill of Rights Act, which enshrines the right to life, and also by declaring a climate emergency it had created "legitimate expectations that you are going to follow them and act in accordance with them."

The door was opened to such legal recourse following court proceedings last March, when Justice Edwin Wylie agreed there could be a legal duty to recognise the impact of climate change, potentially creating a new area of law.

The case was made by Climate Change Iwi Leaders group chair Mike Smith against Fonterra, Genesis Energy, Dairy Holdings, NZ Steel, Z Energy, NZ Refining and GBT Mining and is now headed for the Court of Appeal. 

To achieve the council's targets of reducing overall city emissions by 50 percent over the next nine years and getting to net zero emissions by 2050, its transport plan is focused on investment in cycleways, implementing policies promoting the uptake of low emission, heavy freight vehicles and improving public transport options.

But the former Bell Gully partner, representing the 350 legal and academic members of the climate action group, said while the council's goals were admirable, "failure of the council to follow its own policy would certainly be something that could be viewed by the courts." 

Maungakiekie-Tamaki councillor Josephine Bartley said it "sucks" to have the action group come to the committee and sound "like they want to sue us."

In response, Cooper said while the group "didn't want to sue anybody. But ultimately the action is necessary and unfortunately it takes political courage to do it."