Definitions of unlawful assembly
the crime of gathering together with a group of other people to disturb the peace or to commit another crime
Some of the protesters have been charged with unlawful assembly and could face considerable prison terms if convicted.
the illegal gathering together of a group of people eg for an unlawful protest or demonstration
Police formed a line blocking the north side of the plaza and, to the confusion of everyone in attendance, declared over a loudspeaker that this was an unlawful assembly and that everyone had to disperse or face police action.