A judge rejected claims by resident Geraldine Milner that the decision-making process was "defective". Ms Milner brought the application for a judicial review, backed by local anti-fluoride campaign groups.
Other local authorities had put their fluoridation schemes on hold, pending the outcome of the case. The judge expressed sympathy for people who disagreed with fluoridation but said there was no illegality in the decision-making process. He said: "I appreciate that that will deeply disappoint Ms Milner and the many objectors in the affected area, to whose position I am sympathetic. However it is important to stress that our democratic Parliament decided long ago that water can, in certain circumstances, be fluoridated. As I have endeavoured to show, and contrary perhaps to the belief of Ms Milner and others, it is not the law that fluoridation can only occur when a majority of the local population agree. Parliament has firmly entrusted area-specific decision making to the relevant strategic health authority (SHA). This SHA have not acted unlawfully and no court can interfere with their decision."
During the hearing, Ms Milner's counsel David Wolfe had argued that residents would have "no choice" but to drink fluoridated water.
Campaign groups including the Safe Water Campaign for Gloucestershire, have backed the mother-of-three's case, arguing that the potential side effects range from bone cancer to thyroid problems and brown spots on the teeth.
The decision to add fluoride to water came after 72% of those who responded to public consultation opposed it, with 28% in favour. Mr Wolfe said the authority's move was contrary to government policy that no new fluoridation schemes should be introduced unless it could be shown that the local population was in favour.
Responding to the judgment, Geraldine Milner stated afterwards: “I am obviously disappointed. This is a grim day for justice for the people of Southampton. I am speaking with my legal team with regard to an appeal and sincerely hope to continue the fight.”
There now needs to be a decision as to whether to appeal.
Doug Cross writing in UK Councils Against Fluoridation still challenges the legality of the view saying: "Adding fluoride to the public water supply is therefore a clinical intervention. As such it would be in gross violation of medical law and clinical Codes of Practice. So in summary, therefore, water companies can be ordered to make the product - but they cannot then supply it to the public! And it is this argument that will undoubtedly now replace the entirely valid, but sadly peripheral scientific objections to this discredited practice. Already there is public despair at a ruling that appears to allow the State to dose the people with whatever substance may be in medical fashion, in arrogant disregard of the wishes of the people."
But this judgment does NOT endorse the continuation of the practice of water fluoridation. It merely establishes that the government has given a legitimate power to SHAs to order water suppliers to make a medicinal product. In does NOT permit the product to be used in the mass medication of the public."
The balance of public opinion around the world has already started to swing against water fluoridation, as witnessed by events in the USA, Canada and elsewhere in the past month. This form of State-sponsored clinical malpractice is rapidly coming to an end - this judgment merely ensures that far more pressure will now be exerted to force its long-overdue demise."