A man who claimed that alert level 4 placed him and his family in "detention" has had his court case against Prime Minister Jacinda Ardern and Director-General of Health Dr Ashley Bloomfield dismissed.

The man, who cannot be identified, went to court seeking a writ of habeas corpus, which declares that someone's detention is unlawful.

If successful, the man would have been released from coronavirus lockdown restrictions.

The case, which was also brought against director of Civil Defence and Emergency Management Sarah Stuart-Black, was heard by Justice Mary Peters at the High Court in Auckland last week.

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On Thursday, the court dismissed the application.

Ardern's counsel Austin Powell said people were subject to significant limits during lockdown, but had the autonomy to make decisions about essential travel.

"There is no requirement that you obtain permission in advance or that you report on your movements," Powell added.

KATHRYN GEORGE, AARON WOOD/STUFF Here's what you can and can't do while New Zealand is on lockdown, under Level 4 alert for Covid-19 (video published in March).

He said the Covid-19 alert levels imposed no demand people stay in their homes for a minimum number of hours each day.

"This doesn't get far enough to be considered a detention."

Justice Peters agreed that she did not consider the man's family to be detained as they remained free to engage in many of their usual activities.

"In my view, the freedom to exercise whenever they wish, to go to the supermarket whenever they wish, to talk to whomever they wish, and to access the internet whenever they wish is quite different from being held in custody," she said.

The man was also on home detention until July, the judgment said.

"On a comparative basis, the extent of the restrictions imposed by the lockdown is still some distance short of the effect of home detention," Justice Peters said.

The man had earlier said a model predicting 80,000 New Zealanders would die without lockdown was in his opinion an inaccurate "well-woven yarn of complete decimation".

He said restrictions on hunting and swimming followed a "fallacious" premise hospital emergency rooms were too busy.

"We'll be dealing with a corpse, the corpse of rights," he added.

However, Justice Peters said the man and his family were not subject to detention within the meaning of the law.

"If I am wrong, and they are detained, the detention is lawful," Justice Peters said.