Police had warned people attending protests in support of the proscribed group they could be arrested if they held up placards in support of the banned organisation.
More than a hundred protesters gathered outside the US embassy in Nine Elms, London, with the Met Police saying the majority of the 48 arrests made were for “expressing support for a proscribed organisation”.
Another demonstration took place at the US consulate near Holyrood in Edinburgh in support of the group.
Defend Our Juries, which is organising the demonstrations, said protesters will hold up signs reading “I oppose genocide, I support Palestine Action”.
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Expressing support for the group is an offence under the Terrorism Act after it was proscribed in June 2025.
The protests come ahead of an appeal at the Supreme Court against Palestine Action’s designation as a terror group on 4 November.
A retired lawyer who travelled from his home in Cumbria to attend the protest on Saturday said he was demonstrating because he “feared for our liberties”.
Charles Allison, 75, told the Press Association: “I decided that I ought to try and do something, and this is the little bit that I’m doing.
“I fear for our civil liberties, which are being devalued and watered down, even by this new Labour Government.
“So I’m dejected, but enthused that there are so many wonderful people protesting.”
He added: “I speak as an ex-lawyer, so it’s uncomfortable for me to break the law deliberately. But I felt that I could do no other.”
Mr Allison was taken away by two police officers just before 1pm, after he was told he posed a “threat”.
The Metropolitan Police said a Section 35 dispersal order was in place in parts of London, covering the embassy grounds, from 8am to 11pm on Saturday.
The force said the measure, which means people can be ordered to leave the area or face arrest, followed “information that a group are planning to attend an event and express support for a proscribed organisation”.
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