This case focuses on the work of the Departmental Unit of Yvelines (Versailles Province) of the French Democratic Confederation of Labor (CFDT-Ivelines) to advance the campaign for regularization of undocumented immigrant workers. Although the national CFDT was involved in the national campaign jointly with the CGT, it remained less involved at the local level except for CFDT Yvelines. The case examines a number of specific instances in which the union supports immigrant workers in their sit-in strikes in their workplace as well as in community facilities, providing specific examples of the ways in which the campaign strategy succeeded in putting pressure on employers to support the regularization of undocumented workers. It is of note that in contrast with the overall thrust of the regularization campaign, CFDT-Yvelines supported undocumented workers' efforts without requiring immigrant workers to be or become union members.