The country’s largest iwi by land size is preparing to renegotiate parts of its landmark Treaty settlement amid major reforms to conservation law which the iwi says will strip it of power.

It comes after the iwi, Ngāi Tahu, took the Crown to court over the Conservation Amendment Bill, which marks the most significant changes to the country’s conservation law in almost four decades.

Ngāi Tahu, with an area of interest that covers most of the South Island and much of the country’s conservation estate, is one of the more vocal critics of the law change.

It would open conservation land for economic development, increase the number of concessions granted and change the way conservation boards operate.

The Government says this is to streamline and modernise outdated legislation and improve slow processes that have created unnecessary cost and delay.

Many iwi have Treaty settlements that provide roles in certain conservation processes such as management planning and concession allocation.

The Ngāi Tahu settlement, for example, provides for one iwi-elected member to sit on the national-level statutory body, the New Zealand Conservation Authority, and for the regional level conservation boards to consult with the iwi when considering certain policies and plans.

The amendment bill reduces some of the powers available to conservation boards and the Authority.

Ngāi Tahu kaiwhakahaere Justin Tipa said the amendment strips power from the iwi “by turning those boards and the Authority into advisors only and handing decision-making powers to the Minister.”

“Ngāi Tahu was guaranteed a voice on the New Zealand Conservation Authority and conservation boards which currently hold decision making powers.”

The original Conservation Act includes a strong and broad clause that requires the Crown to uphold the Treaty of Waitangi and its principles.

The new amendment bill adds a clause that provides ways to implement the original clause.

Law firm Anderson Lloyd describes it as “effectively attempting to codify what is in, and what is out”.

The new bill requires the Crown to work with settlement organisations to seek agreement on how Treaty settlement redress would operate “with the same or equivalent effect to the greatest extent possible in the new system”.

Ngāi Tahu’s concerns centre on this wording and fears that “the greatest extent possible” implies there may be some parts of the original agreements that might not be able to be upheld.

“The Bill includes proposed arrangements to uphold Treaty Settlements, but it puts iwi in the position of being forced to renegotiate important parts of their settlements to fit within a narrow framework.

“Under the new regime, where elements of a settlement do not fit neatly within that framework, the Crown would only be required to meet them ‘to the greatest extent possible’. In no world does that align with a ‘full and final’ settlement.”

Conservation Minister Tama Potaka said because the new bill will change the nature of things like conservation boards the Government will need to negotiate with iwi over the coming years to find agreeable solutions that are “equivalents” to what already exists.

“You can’t get something exactly the same, so we have got to work through [those issues] with iwi over the next couple of years, and until that time the iwi will continue to have someone on that board,” Potaka said.

“Some iwi will say we settled our claims on the basis of this RMA [the overarching legislation], now it is going to be something different we want a renegotiation of all the claims.

“There are some people who are saying that’s what we should do ... what we are intending to do with the Conservation Act is actually work through something of equivalence, something very similar even though it might not exactly be the same and that I think is done in good faith.”

Tipa says Ngāi Tahu is being forced back to the negotiating table which “will likely lead to long and costly disputes over what is or isn’t equivalent for something we understood to be settled nearly three decades ago.

“This is about protecting the Ngāi Tahu settlement. We are not seeking anything more than that. Put simply, the Crown needs to uphold its end of the bargain.”

Tipa said the iwi were “absolutely up” for the discussion of making improvements to the conservation system but “the commitments the Crown made through our settlement must be honoured”.

“We are concerned we will be spending time and money relitigating decisions and processes that are already established and well regarded, rather than focusing on what matters.”