London police arrest 139 outside U.S. Embassy as hundreds protest UK ban on Palestine Action ahead of Supreme Court appeal

London police arrested 139 people on Saturday as hundreds of demonstrators gathered outside the U.S. Embassy to protest Britain’s ban on Palestine Action and openly declare support for the proscribed group.

The Metropolitan Police said the majority of those detained were arrested on suspicion of expressing support for a proscribed organisation, an offence under Britain’s Terrorism Act.

Protesters gathered outside the embassy in Nine Elms, south London, with many holding signs reading: “I oppose genocide, I support Palestine Action.”

The demonstration was organised by Defend Our Juries, which estimated that about 400 people attended. Police did not provide an official crowd estimate.

Palestine Action was proscribed by the British government in 2025, making membership of or support for the organisation a criminal offence. The group is known for direct-action campaigns targeting companies and facilities it accuses of supporting Israel’s military.

Saturday’s arrests came just days before the UK Supreme Court is due to hear an appeal on Nov. 4 challenging the proscription.

The High Court earlier this year ruled that the ban was disproportionate, but it remained in force while the government appealed. The Court of Appeal subsequently upheld the proscription in June.

Defend Our Juries says more than 4,000 people have been arrested for defying the ban since it took effect, though that figure is the campaign group’s count rather than an official police total.

A parallel demonstration was held outside the U.S. Consulate in Edinburgh. No arrests were reported there on Saturday, although Police Scotland said it was reviewing evidence involving people displaying banners and clothing supporting Palestine Action.