London police arrested 532 people on Saturday after supporters of the recently banned group Palestine Action staged a protest to challenge the government’s enforcement of the ban.

Most were detained for displaying signs supporting the proscribed organization, with others arrested for offenses such as assaulting officers.

The group, outlawed for past violent actions and property damage, argues the ban unlawfully restricts free speech, while officials maintain it targets a group engaged in serious criminal activity, NPR has reported.

Nearly half of those arrested were over 60, and police say decisions on charges could take weeks as counterterrorism officers prepare case files.

Written by B.C. Begley