In spring 1915, the delicate issue of French factory workers fabricating sandbags for the German army led to various breaches of public order in occupied Roubaix. These workers were criticized and physically assaulted by their occupied compatriots. At roughly the same time, many such workers refused to continue working for the German military authority. This unrest continued for months, putting the French administration, especially the local police force, in a difficult situation: these civil servants sought to restore public order and avoid punishments for the population, but did not want to encourage working for the Germans. Scandals involving policemen further undermined this challenging task. This article examines and explains these understudied events in detail, considering the nature of public disorder, the narrative of the “sandbag affair,” and the problems faced by the police. This allows for an insight into occupied life, especially the primacy of public perception and judgment.