Most incidents of urban unrest in recent decades - including the riots in France, Britain and other Western countries - have followed lethal interactions between the youth and the police. Usually these take place in disadvantaged neighborhoods composed of working-class families of immigrant origin or belonging to ethnic minorities. These tragic events have received a great deal of media coverage, but we know very little about the everyday activities of urban policing that lie behind them.

Over the course of 15 months, at the time of the 2005 riots, Didier Fassin carried out an ethnographic...