Nether Edge Green Party councillor, Alison Teal, was served with a legal notice for her involvement in protests against Sheffield City Council's tree felling programme.
Ms Teal was previously arrested for protesting against the tree removals.
Charges against her and 13 others were dropped earlier this year.
More stories from across Yorkshire
Sheffield City Council maintain that the removal of street trees in the city is lawful and necessary.
A "pre-action protocol letter" from the council's legal department to Ms Teal warned the authority will seek a High Court injunction to stop her, and others involved in "direct action", from taking part in future protests.
The council said the process would give protesters "a chance to further and finally consider their position" before it begins legal proceedings on 12 July.
Councillor Bryan Lodge, cabinet member for Environment and Street Scene, said there had been months of "unlawful and costly disruption" to tree replacement works in Sheffield by a small number of protesters.
"We continue to support the right to peacefully protest, and the majority of protesters who are doing so peacefully will not be affected," he added.
"But there is a big difference between this and direct action which deliberately and unlawfully stops works from being carried out."
Mr Lodge said protesters had been sent a letter several weeks ago confirming their actions were unlawful.
"Streets Ahead is not just about street trees, it's about ensuring we have roads, pavements and a street scene to be proud of for many years to come," he added.
"In addition, it presents us with a unique opportunity to sustainably manage, increase and maintain our diverse street tree stock over a 25 year period."
The council said, despite the letter, works were still being disrupted "causing city-wide delays".

Mostly they land upright with a reassuring thud on the crash mats.
There are dozens of children taking part. Kirkcaldy gymnastics club is noisy and life-affirming. It's a strange place to find a dying man.
Gordon Aikman has motor neurone disease (MND). He was diagnosed at 29. This cruel condition is shutting down his body. There's neither a cure nor an effective treatment.
But Gordon refuses to give in without a fight. He's raising money for research and campaigning for better patient care.
His old gymnastics club is donating Â£700. Gordon competed for and coached at Kirkcaldy.
It's January 2015 - seven months after doctors gave him the devastating diagnosis.
He can still walk with a crutch and he drove himself here from Edinburgh.
But his days as a gymnast are behind him.
"It's difficult" he says. "I've looked back at pictures of me doing handstands and cartwheels and I love exercise and sport.
"And I still dream of being able to run but I can barely walk, so it's a dream I'm not going to realise again."
Throughout 2015, Gordon's physical condition deteriorates.
He has to give up driving. An electric wheelchair replaces his crutch. Carers help him feed, wash and dress.
And there's worse to come.
"The thing that I'm most scared of is losing my voice," he says.
"I think that would be incredibly difficult. So, not only are you paralysed, unable to move, you're then suddenly not able to communicate and speak."
As an insurance policy, Gordon banks speech samples with an Edinburgh university team who are developing a voice synthesizer.
He also secures new rights, for all those who lose their speech, to access voice technology.
As Gordon's body weakens, his campaign - Gordon's Fightback - is going from strength to strength.
It's on course to raise Â£500,000 for MND research.
It has convinced the Scottish government that the NHS, rather than charity, should fund a team of specialist MND nurses and double their number to 12.
Gordon's inspiring example has been widely recognised.
His awards include the British Empire Medal, an honorary doctorate from Edinburgh University and the Public Campaigner of the Year title at the Scottish Politician of the Year Awards.
Yet Gordon is modest about his achievements.
"It's what I could do," he says. "It's what I could give back. It's how I could make a difference".
Gordon Aikman's story is told in a new BBC television documentary. The Fight of Gordon's Life will be broadcast on BBC1 Scotland at 20:30 on Monday.
A council is to seek a civil injunction and damages against one of its own councillors and other members of the public.
[NEXT_CONCEPT]
They run, jump and hurl themselves through the air.