We propose a logical framework to represent and reason about some important aspects of a theory of institutional action: (1) the distinctions between physical facts and actions and institutional facts and actions; (2) the distinction between causality and ‘counts-as’; (3) the notion of institutional power. Technically, our contribution consists in extending a dynamic logic of propositional assignments with constructions allowing to express that an agent plays a given role; that a physical action causes another physical action; that a physical action performed by an agent playing a given role counts as an institutional action.