Environmentalists and residents of a small island are celebrating a "significant" court win in their bid to protect fish and seabirds.

Six elderly kuia and kaumātua from Motiti Island took on the combined might of the Crown, local government, powerful iwi and the commercial fishing industry.

The tiny hapū won, backed by Forest and Bird "groundbreaking" rulings in the Environment and High courts in 2017 that gave local councils powers to regulate fishing to protect native species. But the Government appealed the decision.

Now the Court of Appeal has ruled regional councils can use the Resource Management Act to control fishing to protect biodiversity.

"It's absolutely significant," says Forest and Bird lawyer Peter Anderson.

"It opens up a whole different range of methods of protecting biodiversity that haven't been utilised."

Hugh Sayers, a spokesman for the Motiti Rohe Moana Trust which brought the action, says it's good news for Motitians.

"We are happy, I think. It is as we expected. This is the clarity that the authorities and council have needed.

"The Government has dragged this out to drain us. And we still have a long way to go to get things put in place by the council."

One of the eldest members of the MRMT, Kataraina "Bunty" Keepa, 88, feared she would die before the case was resolved. "[They] were hoping we would die or go away."

At the heart of the legal battle was a perceived conflict between the Resource Management Act and the Fisheries Act, which allows the Ministry for Primary Industries to regulate and management fish stocks.

MRMT wanted the Bay of Plenty Regional Council to prohibit fishing in the waters around Motiti. But the Government, MPI and the fishing industry said that interfered with the Fisheries Act.

The Court of Appeal has found there is overlap between the two acts.

The decision says: "We have rejected the premise ... that a regional council cannot control the activity of fishing where that activity is regulated under the Fisheries Act. We have accepted that it may do so provided it does not act for Fisheries Act purposes."

The decision also sets out five indicators councils must consider when looking to control fishing. They cannot distinguish between recreational and commercial fishing when setting out restrictions.

"These indicia are really important for determining whether a restriction on fishing is lawful and when it is not," says Anderson.

Forest and Bird will now continue to contest a coastal plan in Northland, a case which was on hold pending the appeal.

The trust and the Bay of Plenty Regional Council are currently mediating over appropriate fishing controls to be put in the district plan. Once that is settled, the minister of conservation must sign off on the plan.

THE EIGHT-YEAR FIGHT

The container ship MV Rena hit Ōtāiti (Astrolabe Reef) in October 2011, spilling 350 tonnes of oil and affecting countless fish and up to 20,000 seabirds.

Significant pollution from oil, cargo and contaminants spilled out over a large area.

To allow salvage work to take place, Tauranga's harbourmaster put in place an exclusion zone around the wreck. With little to disturb the waters, marine life began to flourish again.

But when it was lifted, overfishing of crayfish and snapper allowed kina to flourish and destroy kelp forests which nourish other species, creating kina barrens.

In 2016, the Motiti Rohe Moana Trust (MRMT) – formed by a group of islanders – asked the Ministry for Primary Industries to extend that protection with a two-year temporary closure of the reef to all fishing: a rahui.

Then-Fisheries Minister Nathan Guy refused, arguing the trust did not have the support of "tangata whenua", infuriating the hapū.

In the experimental case, the hapū teamed up with Forest and Bird to argue that the Bay of Plenty Regional Council could use the RMA to impose marine protection controls, like a ban.

Both the Environment Court and the High Court agreed with the islanders. The Environment Court judges acknowledged that "they have without a doubt established mana whenua over their lands on Motiti and mana moana over Ōtāiti".

But MPI appealed. In June last year, Fisheries Minister Stuart Nash said he backed the appeal because he said the law needed to be clarified.

He threatened to take the fight all the way to the Supreme Court.

The Attorney-General, David Parker, and Nash have been approached for comment.

The decision draws a line under one of the islanders' legal battles.

The group are fighting not only to reclaim their identity and mana, but to take back control of the island. They want to halt years of neglect and environmental degradation, and return Motiti to a thriving economy and community.

The island is wholly privately owned and does not fall under any local authority council and so islanders do not pay rates.

But they also receive no services: no streetlights, no roads, no sewerage. The school closed half a century ago.

The Minister of Local Government (currently Nanaia Mahuta) is a kind of nominal mayor, with day-to-day administration handled by the Department of Internal Affairs (DIA).

To residents, the DIA is both neglectful and a thorn in their side. Since the 1990s, islanders have been battling Wellington officials over the future of the island. Who administers the island, who cares for it, who is allowed to benefit from its resources, and who pays?

The Motitians also want the Government to formally recognise their mana whenua.

"We are an island people and that is what makes us different. We exercise mana whenua, mana moana and kaitiakitanga over Motiti Island," says Umuhuri Matehaere, who was born on the island.

-Stuff/Andrea Vance.