Abstract
Drawing on the notion of generative mechanisms as constitutive rules, this paper advocates a shift away from the notion of routines as sources of ongoing change and towards a rule‐based understanding of routines as institutional facts. While the recent practice turn to routines studies has highlighted sources of endogenous change, this paper adopts a Critical Realist stance to investigate exogenous forces that account for the emergence of a new routine. To this end, the paper endeavours to analyse the passing of new legislation in the criminal justice system of England and Wales. By examining what makes the rules of the game change between the Police and the Crown Prosecution Service, the paper explains an instance of institutionalisation in the making. Theoretical and practical implications are discussed. Our contribution stresses that constitutive rules play a pivotal role for recognising, identifying and labelling organisational routines, thus generating order, stability and patterning.