They would dismantle any structures brought into the Octagon, but the protest would continue in another form, Arthur Taylor said.
"We're not leaving," he said.
Mr Taylor said the occupation was peaceful, but protesters against Covid-19 vaccine mandates had feared how far authorities might go in enforcing clearance of the site.
The Dunedin City Council had been reasonable, "up until a few days ago", he said.
A formal warning signed by council chief executive Sandy Graham, addressed to occupiers, was delivered by two council staff to the Octagon encampment on Thursday.
It said the protesters were in violation of the Reserves Act 1977 and the city’s Reserves and Beaches Bylaw by occupying the area and putting up tents, lighting fires and erecting signs.
"These are offences punishable on conviction in the District Court [with] fines and can result in a criminal conviction being entered against you individually," the letter warned.
The council "wishes to give you the opportunity to cease this offending and leave the Octagon Reserve".
"Should you refuse or fail to leave the Octagon Reserve after this warning to leave, each of you will be committing an offence under the Trespass Act 1990."
Dunedin Mayor Aaron Hawkins has said the Octagon occupiers can continue to protest lawfully, but all tents and other structures would need to be removed by noon on Monday.
In response, protesters called for more supporters to join them and they asked supporters to write to the council.
The council had turned off the supply of electricity to the reserve and a portable toilet provided by a private contractor was removed.
Protesters began their occupation on February 11.
Mr Taylor, who has described himself as a legal and human rights advocate, said the objective was still to "make the point to the Government that they've gone too far".
The Government no longer required vaccine passes to be shown for entry into such places as cafes and mandates have lapsed for many workers.
Mr Taylor remained concerned about mandates keeping health workers out of employment.
"We need those health workers back," he said.
Government interventions to limit spread of Covid-19 had not provided a proportionate response to the virus, he said.
Other diseases had a far higher mortality rate and this had not inspired the same government intrusions on freedom, he said.
Mr Taylor said the protest had not been disruptive and people had been allowed free access to the Octagon.
The protesters could have argued that shelter was an essential adjunct to the right to protest, he said.
Mr Taylor suggested the mayor was motivated by a need to improve his re-election prospects.
Health officials have argued Covid-19 restrictions have been necessary because of the infectiousness of the virus and to prevent the health system from being overwhelmed by a high case-load.
Some 604 people were in hospital today with Covid-19, including 26 in Otago and Southland, the Ministry of Health reported.
Twelve more deaths were recorded of people with Covid through New Zealand and 22 people were in intensive care or a high-dependency unit.
Mr Hawkins has described the group in the Octagon as small and had said its occupation was largely peaceful, but there was now no clear purpose for it.
"There is certainly a level of frustration in the community about the ongoing nature of their presence in the Octagon."
In a message on the Telegram platform, protesters said a decision had been made to dismantle the camp peacefully.
"We have been the most successful Freedom Camp in New Zealand, standing for 60 days."
