London (CNN) A police order banning the global environmental movement Extinction Rebellion from staging protests in London was "unlawful," London's high court ruled Wednesday.

London's Metropolitan Police issued a revised Section 14 order last month when thousands of protesters took to the city's streets, stating that "any assembly linked to the Extinction Rebellion 'Autumn Uprising' ... must now cease their protest(s) within London."

The police imposed the four-day ban on October 14 -- the final week of the movement's two-week campaign of civil disobedience in the city -- prohibiting any assembly of more than two people linked to the October protests dubbed the "Autumn Uprising."

Section 14 of the UK's Public Order Act 1986 is aimed at preventing "serious public disorder, serious damage to property or serious disruption." Critics said the decision to deploy it for the Extinction Rebellion protests was an overreach of police powers.

In his ruling on Wednesday, Lord Justice Digemans 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 Section 14 of the 1986 Act.

"The XR autumn uprising intended to be held from October 14 to 19 was not therefore a public assembly ... therefore the decision to impose the condition was unlawful because there was no power to impose it under Section 14 of the 1986 Act."

However, he also noted that there were powers within the act which might be lawfully used to control future protests deliberately designed to "take police resources to a breaking point."

Extinction Rebellion's campaign of nonviolent civil disobedience centers on mass arrests.

'A landmark decision'

Tobias Garnett, a human rights lawyer with Extinction Rebellion's legal strategy team, told CNN: "We're overjoyed. It is a landmark decision in a way that it reaffirms our right to protest and it makes clear to the police that they are not going to be allowed to use powers that they don't have."

In a statement, the Met said it was disappointed with the ruling and would now "carefully consider the judgment before deciding on our next steps."

Since it launched a year ago, Extinction Rebellion has grown into an international movement. The decentralized organization has attracted tens of thousands of protesters to participate in nonviolent civil disobedience aimed at forcing government action on the climate crisis.

During the shutdown in the heart of London, which began on October 7, protesters targeted areas around Parliament, the Bank of England and London City Airport. Police had tried to restrict the protesters to Trafalgar Square, in central London, under Section 14.

The Met has said more than 1,800 people were arrested during October's non-violent action, 400 of them after the ban was introduced, including Green Party co-leader Jonathan Bartley. As of November 6, 165 had been charged.

The fortnight-long protests cost the police at least £24 million ($31 million) -- higher than the £15 million the Met spends annually on its violent crime taskforce -- and 21,000 officers were placed on 12-hour shifts during the October campaign.

Photos: The Extinction Rebellion protests Extinction Rebellion climate change protesters demonstrate during a rally in Trafalgar Square in London on Wednesday, October 16. Climate protesters in London have kept up their campaign despite being ousted by a police order from their Trafalgar Square encampment on Monday. Hide Caption 1 of 35 Photos: The Extinction Rebellion protests Climate activists hold a banner after climbing atop the roof of the entrance to YouTube's offices in London during the 10th day of demonstrations on October 16. Hide Caption 2 of 35 Photos: The Extinction Rebellion protests The Guardian newspaper environmental journalist and author George Monbiot, right, sits blocking a road with the Co-Leader of Britain's Green Party Jonathan Bartley at the bottom of Trafalgar Square on October 16. Hide Caption 3 of 35 Photos: The Extinction Rebellion protests An Extinction Rebellion climate protester sits atop a fence pillar on the perimeter of the houses of parliament in London, on Tuesday October 15. Hide Caption 4 of 35 Photos: The Extinction Rebellion protests Protesters demonstrate outside the BlackRock headquarters in Throgmorton Avenue in London on Monday, October 14. Hide Caption 5 of 35 Photos: The Extinction Rebellion protests A protester stands near a policeman during a demonstration in London. Hide Caption 6 of 35 Photos: The Extinction Rebellion protests A young child waves an Extinction Rebellion flag outside of the Bank of England during the eighth day of demonstrations October 14. Hide Caption 7 of 35 Photos: The Extinction Rebellion protests Doctors join Extinction Rebellion activists to demonstrate for the sixth day running in Trafalgar Square on October 12. Hide Caption 8 of 35 Photos: The Extinction Rebellion protests Protesters block a road during an Extinction Rebellion protest on Saturday, October 12, in Prague, Czech Republic. Hide Caption 9 of 35 Photos: The Extinction Rebellion protests Oisin O'Connor and his sister, Eve, help wallpaper the front of the Department of Communications, Climate Action and Environment in Dublin, Ireland, on Friday, October 11. Hide Caption 10 of 35 Photos: The Extinction Rebellion protests Activists bury their heads in the sand on Sydney's Manly Beach on October 11. Hide Caption 11 of 35 Photos: The Extinction Rebellion protests Protesters chain themselves to barrels on Berlin's Marschall Bridge. Hide Caption 12 of 35 Photos: The Extinction Rebellion protests Police block the entrance to the BBC New Broadcasting House in London during an Extinction Rebellion protest on October 11. Hide Caption 13 of 35 Photos: The Extinction Rebellion protests Climate activists participate in an Extinction Rebellion protest in New York's Times Square on Thursday, October 10. Hide Caption 14 of 35 Photos: The Extinction Rebellion protests Extinction Rebellion demonstrators block an entrance to the City Airport in London on October 10. Hide Caption 15 of 35 Photos: The Extinction Rebellion protests Extinction Rebellion protesters march as a "human forest" in Dublin. They were heading to Leinster House to call for a complete remodeling of forestry policy. Hide Caption 16 of 35 Photos: The Extinction Rebellion protests A demonstrator displays a banner at the City Airport in London. Hide Caption 17 of 35 Photos: The Extinction Rebellion protests Mothers gather ahead of the Extinction Rebellion "nurse-in" road blockade in London on Wednesday, October 9. Hide Caption 18 of 35 Photos: The Extinction Rebellion protests Extinction Rebellion protesters wear masks in Berlin on October 9. From left, the masks represent German Economy Minister Peter Altmaier, German Chancellor Angela Merkel and German Vice Chancellor Olaf Scholz. Hide Caption 19 of 35 Photos: The Extinction Rebellion protests Extinction Rebellion told CNN on October 9 that activists now control three sites in Berlin. Hide Caption 20 of 35 Photos: The Extinction Rebellion protests Stanley Johnson, father of British Prime Minister Boris Johnson, joins protesters in London's Trafalgar Square on October 9. Days before, his son described Extinction Rebellion protesters as "hemp-smelling," "uncooperative crusties." Hide Caption 21 of 35 Photos: The Extinction Rebellion protests The protests often dip into the theatrical. On October 9, anti-aircraft protesters held signs in Trafalgar Square a day before a planned "'Hong Kong-style occupation" of the London City Airport. Hide Caption 22 of 35 Photos: The Extinction Rebellion protests Activists block a bridge close to the Reichstag building in Berlin on October 9. Extinction Rebellion encourages volunteers to carry out acts of "peaceful civil disobedience to call on government to act on the climate and ecological emergency." Hide Caption 23 of 35 Photos: The Extinction Rebellion protests Activists protest outside Dublin's Government Buildings as Ireland's finance minister unveiled the country's 2020 budget on Tuesday, October 8. Hide Caption 24 of 35 Photos: The Extinction Rebellion protests Climate activists glue themselves to the entrance of a power company's offices in Amsterdam, Netherlands, on October 8. Hide Caption 25 of 35 Photos: The Extinction Rebellion protests Activists stage a sit-down protest outside Dublin's Government Buildings. Hide Caption 26 of 35 Photos: The Extinction Rebellion protests Protesters wearing black stand next to a coffin as they stage a demonstration in front of Berlin's Brandenburg Gate on October 8. Hide Caption 27 of 35 Photos: The Extinction Rebellion protests A man is detained in Melbourne as he takes part in an Extinction Rebellion protest on Monday, October 7. More than 50 people were arrested throughout Australia that day. Hide Caption 28 of 35 Photos: The Extinction Rebellion protests In New York, demonstrators congregate at Washington Square Park as they launched actions around the city on October 7. The protests included pouring fake blood over Wall Street's Charging Bull statue. Hide Caption 29 of 35 Photos: The Extinction Rebellion protests The Red Brigade surrounds police in London on October 7. This crimson-robed troupe is common at Extinction Rebellion protests and is the creation of the Invisible Circus, a street performance group. Hide Caption 30 of 35 Photos: The Extinction Rebellion protests A driver watches protesters block a city intersection in Melbourne on October 7. Hide Caption 31 of 35 Photos: The Extinction Rebellion protests Extinction Rebellion flags fly at a protest in Melbourne. Hide Caption 32 of 35 Photos: The Extinction Rebellion protests A group calling itself the Aged Agitators demonstrates outside London's Houses of Parliament. Hide Caption 33 of 35 Photos: The Extinction Rebellion protests A woman sits down in front of a line of police in Melbourne. Hide Caption 34 of 35 Photos: The Extinction Rebellion protests Protesters take part in Extinction Rebellion's global "Week of Action" in Melbourne. Hide Caption 35 of 35

Assistant Commissioner Nick Ephgrave said in a statement: "The decision to apply the conditions on 14 October on the Extinction Rebellion 'Autumn Uprising' protest was not taken lightly."

Ephgrave described the situation at the time as "untenable," saying protesters had created "unacceptable and prolonged disruption to Londoners."

He continued: "After eight days of continual disruption we took the decision to bring an end to this particular protest, a decision which we believe was both reasonable and proportionate.

"I want to be clear; we would not and cannot ban protest. The condition at the center of this ruling was specific to this particular protest, in the particular circumstances at the time."

The court ruling could lead to more legal action against the police, as protesters detained under the ban could seek compensation for unlawful imprisonment.

Ellie Chowns -- a Green Party Member of the European Parliament who was arrested and kept in a police cell for five hours under the blanket ban -- said the ruling was a "very important victory for the principle for the right of assembly and the right to protest, which is so central to a functioning democracy."

She added: "This is a very important judgment because it is going to make the police think twice about putting in place such blanket conditions, and sweep up people behaving in a perfectly reasonable and democratic manner."