Policies related to inter-municipality conducted in France during the past two decades have explicitly asserted solidarity as an essential commitment. Hence, one may consider that social action, whose goal is to reduce inequities and to promote local cohesion, should lend a prominent role to this level of public authority and participate in producing inter-municipal spaces of solidarity. Indeed, associations of municipalities are active in this respect, but social action still depends in most cases on local municipal initiatives. In other words, competence in terms of social action is seldom transferred to public inter-municipal cooperation entities. Based on this observation, the authors seek to analyse the mechanisms that tend to maintain social action as a prerogative of isolated municipalities. They further focus on processes that induce a number of territories to “inter-municipalise” their social policies.