Based on the Elaborated Social Identity Model of Crowd Behaviour, we tested in two experiments whether a forceful display of police power increases perceptions of illegitimacy of the police and the formation of resistance among protestors. In the high power condition, the police were dressed in riot gear (with helmets, armed with shields and batons). In the low power condition, the police were dressed in regular uniforms. In both studies, people participated in a demonstration against right‐wing populism using a virtual reality setting and were either stopped by the police in riot gear or by the police in regular uniforms. The results of Study 1 (N = 155) show that the police in riot gear were evaluated as more illegitimate compared to the police in normal clothing. The results of Study 2 (N = 97) replicated this finding and illustrated that police in riot gear (compared to regular uniforms) increased protestors' intentions to engage in direct resistance against the police. This effect was mediated by perceptions of illegitimacy and anger directed at the police. Furthermore, weakly identified protestors were particularly affected by the display of power and were more likely to engage in anti‐police resistance and collective action. Implications are discussed.