Around 400 supporters of Palestine Action face arrest by the Metropolitan Police when they gather for a demonstration outside the US embassy on Saturday.
Campaign group Defend Our Juries has invited participants to display signs reading: "I oppose genocide, I support Palestine Action".
Expressing support for the proscribed group constitutes an offence under the Terrorism Act, following its ban in June 2025.
Scotland Yard stated that demonstrations linked to Palestine Action "take significant police resources away from the neighbourhoods and communities where they are most needed". Figures obtained through a freedom of information request showed the Met spent £1.3 million policing six "Palestine-Israel public order events" across June and July 2026.
Defend Our Juries noted that its planned action comes ahead of a Supreme Court hearing regarding the ban. Commenting on why the US embassy was chosen, the campaign group said the US had "not shied away" from involvement in the Palestine conflict. In August, the US government imposed sanctions on Palestine Action, classifying it as a terrorist organization.
Met Commander Adam Slonecki, leading the operation, said: "All those intending on coming to this event know that supporting a proscribed organisation is unlawful – they are essentially meeting to purposefully commit a crime.
"The public would rightly expect us to be proactive and not just stand by and wait for offences to be committed. I want to be clear – it is not just those who hold up placards who should expect to be arrested.
"Anyone officers consider to be playing a key role in organising the event, giving instructions to others and/or providing logistical support will very likely be committing an offence and face enforcement action.
"This is not about preventing people from expressing their views, but about acting robustly in cases where doing so involves criminality.
"These events also take significant police resources away from the neighbourhoods and communities where they are most needed. I would urge anyone planning on attending to reconsider."
In June, five Court of Appeal judges concluded that banning Palestine Action was a "justified and proportionate" restriction on freedom of expression. That decision reversed a High Court ruling from February, in which three judges deemed that the decision by then-home secretary Yvette Cooper to proscribe the organisation was unlawful, following a legal challenge by co-founder Huda Ammori.
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