In autumn 2009, a «scavenger square» was opened at the Porte Montmartre in the 18th arrondissement of Paris as an institutional response to the requests of street vendors who gained the support of residents and militants in advocating for a possibility to sell their products legally. This experimental space monitored by social workers authorizes nearly a hundred vendors to resell scavenged goods. Our article proposes an analysis of its practical implementation as a sort of street bureaucracy. After a presentation of the multiple worlds which make up the informal market, we provide an overview of the political reluctances towards this legalization of street vending. We then focus on the social workers’ difficulties in running an institutional outpost in a world which initially developed autonomously. We will underline how the emerging misunderstandings and contradictions led them to readjust their practices and redefi ne the objectives of their mission.