Extinction Rebellion have won a High Court challenge against the Metropolitan Police over a London-wide protest ban imposed during their 'Autumn Uprising' last month.
The force imposed a blanket ban on the assembly of more than two people linked to the climate change activism group, after their protests caused mass disruption in the capital.
But two senior judges ruled the decision to impose the ban, made under Section 14 of the Public Order Act, was "unlawful".
Lord Justice Dingemans and Mr Justice Chamberlain said the Act does not cover “separate assemblies” and therefore the Met had no power to enforce it.
Lord Dingemans said: “Separate gatherings, separated both in time and by many miles, even if coordinated under the umbrella of one body, are not a public assembly within the meaning of ... the Act.
“The XR Autumn Uprising intended to be held from October 14 to 19 was not therefore a public assembly.”
However, the judges noted there are powers within the Act which may be used lawfully to “control future protests which are deliberately designed to ‘take police resources to breaking point’” - one of XR’s stated aims.
The 10-day mass demonstrations, which included the blocking of bridges and major roads as well as rallies on the London Underground, were an attempt to demand immediate government action on climate change.
Police said just over 1,800 people were arrested and the court heard that policing the protest cost more than £20 million.
Ellie Chowns, a Green MEP who was arrested while the ban was in place, said she was "absolutely delighted" by the ruling.
"The judgment in our favour shows that the police clearly overstepped the mark when they imposed a blanket ban on any XR related protest. It was clearly ridiculous to arrest me for simply standing in Trafalgar Square, a pedestrianised public space.
"This judgment upholds the right to peaceful assembly and protest, a fundamental cornerstone of our democracy."
The Met Police said it was "disappointed" with the ruling but will "respect the decision of the court".
Assistant Commissioner Nick Ephgrave said the decision to apply the ban was "not taken lightly" and that the force "would not and cannot ban protest".
He added: “There is no criticism from me of the decision to impose the condition, which was made with good intent and based upon the circumstances confronting the command team at the time. It did in fact result in the reduction of the disruption. Nevertheless, this case highlights that policing demonstrations like these, within the existing legal framework, can be challenging.
“We will carefully consider today’s ruling.”