This study examines the policies applied to French immigrants in Aragon between 1635 and 1697, a period of economic decline and constant conflict between Spain and France. The commercial and tax measures imposed by the Spanish monarchy on French immigrants to support the war effort were opposed and constrained by Aragonese institutions, such as the Diputación or the Corte del Justicia de Aragón. After a period of debate the Aragonese Parliament developed an autonomous policy towards the end of the seventeenth century. In the interests of the Aragonese economy and elites, restrictions on migrants were lowered and revised, until they focused mainly on merchants. This legislation allowed immigrant flows to continue, but it could not counteract the decline of economic opportunities for the French in Aragon.