Orders to add fluoride to more than a dozen drinking water supplies have been ruled unlawful by the High Court, likely delaying plans for a significant expansion of fluoridation.
In July 2022, then Director-General of Health Sir Ashley Bloomfield directed 14 councils to fluoridate some or all of their drinking water supplies.
He did so under a new law that put fluoridation decisions in the hands of the Director-General of Health, rather than local authorities, where they had previously belonged.
A preliminary High Court decision released on Friday has ruled those orders contained a procedural error - namely, Bloomfield did not give specific consideration to the Bill of Rights Act in making them.
It means the fluoridation orders could be set aside or returned to the Ministry of Health for reconsideration before a substantive hearing on the broader issue next year.
The 14 councils were given a deadline to start fluoridating and would be subject to hefty fines should they fail to comply.
The deadlines ranged between 2023 and 2026. One authority, the New Plymouth District Council, had already begun fluoridating in response to the directive, and several others were planning to do so imminently.
A further 27 councils were told they were being considered for fluoridation directives.
The ruling emerged from a judicial review by New Health New Zealand, a Christchurch-based natural health lobby group.
Amongst the arguments from the group's lawyers was that Bloomfield had to consider the Bill of Rights in his decisions. This question was taken out of the wider review and considered on its own by the High Court.
Under the Bill of Rights, anyone can refuse medical treatment. Fluoride opponents have long argued that mandatory fluoridation breaches that right.
The Supreme Court, however, has previously ruled that councils are allowed to fluoridate and that doing so is a justifiable limit on that right.
On Bloomfield's behalf, the Crown argued that nothing had changed since that decision, and requiring such weighty considerations for discretionary decisions would "unnecessarily complicate and encumber administrative decision-making at all levels of government", the decision said.
If breaches of the Bill of Rights were found, the courts could step in, the Crown argued.
The court disagreed.
In his decision, Justice Paul Radich found that decision-makers were required to show they had considered the Bill of Rights in decisions that touched upon it.
"It is in my view an essential component of the Bill of Rights Act scheme that a shot must be taken at the target by the decision-maker in the first instance before the Court comes to see where it lands," the decision said.
Such a consideration did not need to be "an undue burden," Radich said.
"It should be perceived as a positive and integral part of a society in which fundamental rights are defined and cannot be limited arbitrarily."
While New Health New Zealand had asked for the fluoridation orders to be set aside, Radich ruled that the parties should try to agree on an outcome.
The anti-fluoride lobby group Fluoride Free welcomed the decision, which said the ruling makes suspension of the directives "highly likely".
A Ministry of Health (Manatū Hauora) spokesperson said the decision "has been received and is being considered".
* This story was first published by Stuff.