Te Runanga-a-Iwi o Ngati Kahu chief executive Anahera Herbert-Graves said court action had cost well over $100,000, as well as relationships and even lives.
She believed a series of unexpected deaths - one family lost six members aged under 50 in three months - was related to the battle over the cave.
However, the iwi's commitment and belief had paid off, and she was "cautiously happy" with the result.
She hoped Carrington Farms would accept the judgment, but it could appeal all the way to the Supreme Court.
Ms Herbert-Graves was grateful to the runanga's legal advisers who had held fast to the belief that New Zealand law protected the sacred sites of Maori.
"But most appreciated of all is the sacrifice of those who mortgaged their homes and donated funds to fight the council and Carrington," she said.
Runanga chairwoman Margaret Mutu said Mr Kelly had known about the wahi tapu since 1999, when kaumatua Dick Urlich showed him where the caves were. Mr Kelly had agreed to fence off the area and leave the caves undisturbed, but work had started again after Mr Urlich's death in 2008. Professor Mutu said the developer had told her the out-of-court settlement no longer applied.
The current case had its origins in 2007 when the council granted Carrington a non-notified consent to build 12 houses. It was only in 2009, when Carrington applied to subdivide the land that Ngati Kahu learnt of the earlier consent.
The judge ruled the applications should not have been allowed separately, and Ngati Kahu should have been informed on both occasions.
The Far North District Council is not commenting on the judgments until it has had an opportunity to study them.
The Environment Court appeal against the subdivision was heard in May but the judge's decision was released only on Friday.
Karikari Beach is an as yet undeveloped, 7km-long swathe of white sand which was the scene of a major whale stranding last August.
At the time some kaumatua involved in the rescue said the stranding was a tohu, or a sign, of support for the iwi's battle.
Mr Kelly is a US investment banker who owns Carrington Club golf course, a luxury lodge and winery on 1200ha of land on Karikari Peninsula.
He also owns Edgewater Developers, which specialises in Far North coastal property. He is on the advisory committee of Auckland University's Business School and is a member of the New Zealand Business Roundtable.