Britain’s highest court on Wednesday heard an appeal against the ban on Palestine Action, which the British government classifies as a terrorist organization, as police moved to arrest protesters outside.

A lawyer for the group’s founder argued that only three of 385 acts by the organization cross the legal threshold of terrorism. Twenty-five protesters were arrested outside the Supreme Court on suspicion of expressing support for a proscribed organization, according to the Metropolitan Police. The court heard that more than 3,000 people have been arrested since the ban came into force, and that the High Court found the ban unlawful in February, a ruling overturned by the Court of Appeal in June.