Presumably nobody (except perhaps a few nutters - including a couple of politicians) would want a result that allowed people to be illegally arrested or detained in New Zealand.
As I wrote above it's different to temporarily over reach in the interests of public safety. The government has the power to change the law and, if required, should do so. To do otherwise is to be actually be a police state as opposed to what the conspiracy lunatics like to suggest.
It's an important test of law.
I don't really understand the problem here. I understand what is being said, but I don't follow the logic. Wherever else I have lived, public health always takes precedence over individual rights. This is especially true in Europe, which has a history of contagious diseases. I experienced this personally when I returned an incorrect positive result on a TB test and my civil rights were immediately abrogated as I was kidnapped by ambulance personnel and confined against my will in a hospital quarantine facility. I had no say whatsoever in the matter. After a couple of days, it was determined I did not have TB and I was unceremoniously dumped on the street to find my own way home.
I think after the example of Typhoid Mary, most civilised countries adopted legislation that gives health authorities power to arbitrarily detain individuals who may potentially be carriers of a disease that poses a threat to others. Covid 19 is clearly such a disease. It is contagious and people die from it. This kind of power exists to serve the greater good. It does not mean the end of democracy.
In your case the authorities (presumably) lawfully had that power. The point is whether the New Zealand government lawfully had the power to do what they did. If they didn't then why didn't they enact legislation to give them the power to do what they did, as they did with the Covid-19 Public Health Response Act 2020?
The Ministry of Health has been routinely ignoring the law pertaining to compassionate exemptions and lost in court in the Christiansen case. This is fairly predictable behaviour from most large organisations, which is why there are laws to protect individuals.
The point is that the government can't wave its hands and detain people, there needs to be a legislative framework for this. @dejadeadnz may want to comment further, or not.