Sheffield Council has told tree campaigners they choose to defy court orders at their own risk.
The authority provoked anger among those trying to stop mature street trees being felled when it sent out letters warning of legal action last week.
Campaigners were urged to agree to stay out of safety barriers put up around trees due to be cut down - or face an injunction.
The council says protesters are acting unlawfully by stepping inside the barriers and preventing Amey workers from felling trees as part of the Streets Ahead programme.
If a judge sides with the council, any protester who breaks an injunction will be in contempt of court and could face a fine or prison.
At yesterday's full council meeting - before which campaigners demonstrated outside the Town Hall - Coun Bryan Lodge, cabinet member for the environment, said it was campaigners' own choice to defy a judge.
Responding to a member of the public who asked whether the council was trying to 'crush legitimate opposition' to tree felling, Coun Lodge said there was a difference between 'peaceful protest and unlawful actions'.
"People are allowed to stand outside the barriers, but people are going inside and putting themselves at risk," he said.
"What we are trying to do is get the agreement of people that they will not step inside that barrier."
Coun Lodge said if people chose to protest inside barriers and ignore any court ruling, it was 'their decision'.
He said the council had been 'forced' into taking legal action but did not want anyone to go through the court process.
Campaigner Dave Dillner asked Coun Lodge whether he would take part in a public debate on trees, but the cabinet member said previous attempts had descended into 'shouting matches' and he would rather meet people individually.
Richard Davis presented a petition calling for the Amey contract to be ended on health and safety grounds, based on a conviction for a public safety offence from 2011.
Amey Infrastructure Services and Mouchel Parkman Services were each fined £30,000 after an electrician fell to his death from a cherry picker in Liverpool.
Mr Davis said Amey had failed to disclose the conviction during the bidding process for Streets Ahead.
The petition had seven signatures.
Coun Lodge said the Health and Safety Executive had investigated and decided to take no further action. He said Amey's record was better than the national average.
And Phil Yates, of the Save the Trees of Millhouses Please group, said that by felling mature street trees the council was not taking its responsibility towards air quality seriously enough.
But Coun Jack Scott, cabinet member for transport and sustainability, said that doubling or even tripling the 36,000 street trees in Sheffield would have a 'negligible' effect on air quality and it was more important to focus on vehicle emissions.
The council says it is replacing 6,000 street trees and planting an extra 600.
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