A new deal will enable Maori to ban other New Zealanders from some coastal areas and impose fines of up to $5000 if they don't obey.
The Ngati Porou deal is the first under the contentious Foreshore and Seabed Act, and will allow some East Cape beaches to be closed to public access.
The new Government is to approve the deal this month. Both National and the Maori Party opposed the 2004 foreshore law for very different reasons - but now ministers from the two parties are set to sign off the deal in affidavits to the High Court.
New Maori Affairs Minister Dr Pita Sharples, co-leader of the Maori Party, expects to be briefed on his obligations tomorrow. His party was formed out of opposition to the law - now he will have to explain to his supporters why he is putting his signature to the papers.
Act leader Rodney Hide, the Local Government Minister, said Labour had left the new Government with a "ticking time bomb". He described the deal as a "political and racial carve-up of the nation's beaches".
The deal was negotiated by former Deputy Prime Minister Dr Michael Cullen in August last year. Shortly after, the outgoing Labour Government reported to the United Nations committee on racial discrimination, which was concerned that the Foreshore and Seabed Act disadvantaged Maori.
That report was not publicised.
Contrary to Labour's public assertions that the foreshore law prevented Maori from asserting their title to the coast, the report said the new processes give Maori more rights over the waterline.
Now, concluding the deal promises to be a test of the strength of the fresh coalition arrangement.
Sharples and Attorney-General Chris Finlayson, a National Party minister, must sign the affidavits by January 31. National and the Maori Party have pledged to review the Foreshore and Seabed Act - a post-election concession won by the Maori Party, which wants it scrapped.
Sharples told the Herald on Sunday he would sign the affidavit because it was his job to do so.
"It's my responsibility to do that," he said. "My responsibility is not a personal one. It is what I'm required to do as Minister of Maori Affairs. We're still going ahead with the review."
Finlayson is also likely to face pressure from his party, should the issue capture public frustration as it did in 2004.
Then, the Labour-led Government passed the Foreshore and Seabed Act to stop Maori being able to claim freehold title to the foreshore and seabed, instead offering them the chance to apply to the courts for certain rights if they could prove they had customarily used the coastline.
The National Party enjoyed a surge of support from non-Maori who feared they would be banned from the beaches, and were unconvinced by Labour's compromise deal.
But many Maori were even more infuriated, marching on Parliament to protest the confiscation of their rights to traditional coastal camping, collecting and fishing grounds.
With the support of leaders of many of the biggest iwi, they formed the Maori Party.
But the powerful Ngati Porou iwi - which has maintained undisturbed possession of much of its land and fisheries over the past 170 years - entered into negotiations with the Labour Government. Their deal, the first agreed under the act, also includes the right to veto use of the coast for commercial reasons.
The agreement covers the East Cape from Opotiki to Gisborne - a stretch of coastline along which most land is owned by Maori under communal title. It authorises the iwi to set fishing regulations (which can be made orally) and to change place names.
The deal also allows about 50 hapu to designate some areas "wahi tapu", or sacred. Ngati Porou describes the deed as giving hapu "the right to restrict or prohibit access", and to "police these restrictions or prohibitions". Offences against the restrictions carry fines of up to $5000.
Amohaere Houkamau, Te Runanga o Ngati Porou chief executive, confirmed hapu had identified a number of wahi tapu areas that would be recorded in the court papers, but would not reveal the locations.
"Our custom in this country has been that the average New Zealander can enjoy a picnic lunch on the beach and take an appropriate and reasonable proportion of seafood - that's not a major issue," she said.
However, Houkamau added, in some situations it might not be appropriate for a camper van to park up at a wahi tapu site. "There are enough beautiful beaches on the coast which are not wahi tapu."
In particular areas, called Territorial Customary Rights Areas, the agreement gives Ngati Porou even greater powers - to veto resource consents, and to set or waive conservation rules.
Houkamau said Ngati Porou's focus was on protecting important sites from commercial interests.
"We have enjoyed the luxury of being one of the most isolated regions in the country," she said.
"But our society is changing. There are marinas and ports and things, all those activities, and people buying up land and getting access and developing further commercial operations, even oil exploration."
Gordon Halley, from the Gisborne red rock lobster fishery, said he was concerned about losing access to more of the East Coast.
"There could be hundreds of sites, there could be thousands," he said. "It's always a concern if we are excluded from areas, preventing access to our historical fishing grounds."
But Gisborne mayor Meng Foon said he did not believe many people would be disadvantaged by reduced access to the beach, as 90 per cent of the East Coast population was Maori anyway.