Policy ethnography approaches offer a nuanced and realistic ground-level view of policies which are too often analyzed abstractly from the top. However, the use of these approaches is not limited to producing more precise information. Drawing on fieldwork on the control of welfare recipients in France, the paper shows that ethnography is particularly suited to uncover the structural characteristics of the new wave of public policies in western advanced societies following the decline of the Fordist-Keynesian approach. In particular, the de-objectification of the collective categories established during the process of the welfare state development leads to a more stringent and intense control of welfare recipients. These controls are based on loose criteria defined in situated practices and interactions. The ethnographic description and analysis of these practices makes it easier to trace and criticize the structural transformation of the welfare state in the age of «workfare», providing an illustration of the empirical and theoretical potential of critical policy ethnography.