The protest tactic requires one or more players to participate. The idea is simple -- players place themselves in the path of progression, forming a wall that prevents other players from passing. This is a passive block by design as players must be present to enact the tactic.
This tactic can most successfully be deployed in corridors. Narrow corridors need only one player to participate, but multiple players can line up next to each other to block larger ones.
This tactic can be thwarted by rocket jumping or on servers with friendly fire or momentum transfer. To prevent rocket jumping, select a corridor that is less than 160UUs high (as a single player is 80UUs in height). There is no prevention against friendly fire or momentum transfer countermeasures.