Sheffield Council has insisted it is taking campaigners to court as a 'last resort'.
Eight people will appear before a High Court judge in Leeds today faced with the prospect of being placed under injunctions brought by the authority.
The legal action is as a result of continued protests against tree felling as part of the council's Streets Ahead contract with Amey.
The council says campaigners are protesting inside safety barriers 'unlawfully' and as a result holding up work - which is costing the taxpayer money.
But some people are determined to stand up for their beliefs.
They include Green Party councillor for Nether Edge and Sharrow Alison Teal, along with Alice Fairhall, Calvin Payne, Dave Dilner, Robin Ridley, Graham Turnbull, Paul Brooke and Simon Crump.
The council also served a notice of injunction to an 'unnamed person' - but it is understood no-one else will appear in court.
If the campaigners are served with injunctions and break them they will be in contempt of court, and could face fines or even prison.
Seven people have signed letters promising not to protest inside safety barriers.
A council spokesman said: "Court action is a last resort for the council following months of pointing out to the individuals involved the critical difference between peaceful protest – standing close to a work site but outside the safety barrier – and unlawful trespass, whereby an individual stands inside the barrier and brings work to a standstill.
"A handful of people are therefore causing major disruption and delays to the £2 billion programme which is upgrading roads, paths, street lights and replacing street trees across the city.
"The council’s survey of 350 streets and regular feedback confirms that the majority of Sheffield residents welcome the work and want it completed. Furthermore, if the delays continue then the taxpayers of Sheffield face a potential multi-million pound penalty on the highways contract due to works not being completed on time."
The authority hopes to replace 6,000 of the city's 36,000 street trees by the end of the year, while planting an extra 600.
It says those 6,000 are either dead, dying, diseased or dangerous, or causing damage to the highway.
But those opposed to the felling say it is a cost-cutting exercise and engineering solutions could be found to keep healthy trees.
Campaigners are crowdfunding to cover their legal costs. A demonstration was held yesterday under an elm in Chelsea Road due to be felled.