This paper focuses on prostitution policies and analyzes how a change in public policy (the law on internal security) is interpreted by the profession in charge of implementing it (the police). When the introduction of a new legal instrument (law in the book) exacerbates the tensions between different branches of the law (the sex worker is both a victim of procuring and guilty of soliciting), and when the creation of a new specialized cadre tasked with its implementation disrupts the police system, legal entitlements become defined at the level of prostitution control practices by the police (law in action). The analysis of the successive stages in the implementation of this public policy shows that, in the short run, the political logic (the fight against soliciting) trumps and disrupts the professional division of labor, and that in the medium term, the professional logic (the primacy of the investigation of procurement cases) ends up prevailing.