This study focuses on the rights of linguistic and religious minorities in federal States. First, it begins with an exploration of the “internal” (i.e. the protection of fundamental rights in federal States) and “external” (i.e. the status of federal States in international (human rights) law) dimensions of the issue. Then, it analyses interactions between minority rights and the division of powers in these States. For this purpose, it relies on two complementary perspectives. The first one focuses on minority rights and shows that they constitute substantial limits to the federal and federate authorities’ exercise of powers. The second perspective concentrates on the constitutional norms dividing legislative powers and emphasizes that the protection of minority rights may represent either the stakes or an object of the division of powers. In the former case, the mere existence of such rights can explain particular aspects of the division of powers, while in the latter the Constitution expressly gives federal authorities the responsibility to protect certain rights. The thesis underlines the various consequences of each of these configurations on the judicial interpretation of minority rights. In order to illustrate these observations, it mainly focuses on two legal orders: Belgium and Canada. ; L’étude porte sur les droits des minorités linguistiques et philosophiques dans les Etats fédéraux. Elle commence par évoquer les dimensions internes – la protection des droits fondamentaux au sein de l’Etat fédéral – et externes – la situation de l’Etat fédéral au regard du droit international des droits de l’Homme – de la problématique. Elle analyse ensuite les interactions entre les droits des minorités et les règles répartitrices de compétences dans ces Etats. Elle le fait au départ de deux perspectives complémentaires, chacune privilégiant l’un des termes de la dialectique. La première met l’accent sur les droits des minorités et montre que ceux-ci agissent comme autant de limites substantielles à l’exercice, par ...