Protesters are scattered throughout a city and share the common objective to gather into groups large enough to perform significant actions. They face forces that may break up groups, block some places or streets and seize any communication devices protesters may be carrying. As a consequence, protesters only have access to local information on people and streets around them. Furthermore, formed protester groups must keep moving to avoid containment by adversary forces. In this scenario, protesters need a distributed and as simple as possible protocol, that utilises local information exclusively and ensures a flocking behavior, i.e., the rapid formation of significantly large, mobile, and robust groups.