South Taranaki District Council has been given the go-ahead to fluoridate the water supply in Waverley and Patea.
The Court of Appeal has ruled in favour of the council, rejecting anti-fluoride group New Health New Zealand's argument that fluoridation of water amounted to medical treatment, which the public should therefore have the right to refuse.
The ruling follows a four-year legal battle that began when the lobby group took the matter to the High Court, where the council's right to fluoridate the supply was also upheld.
The Ministry of Health then passed a regulation declaring fluoride was not a medicine, after the High Court recommended it consider passing a regulation under the Health Act to put the matter beyond doubt.
The decision also awards costs to the council. It has been reported the court action has cost it about $250,000, although the Ministry of Health helped fund the case as it was an issue of national interest.