La non-discrimination est une notion en constante évolution. Elle se doit d’être réceptive aux nouvelles formes discriminatoires vécues par les travailleurs afin de garantir un niveau de protection juridique conforme aux exigences internationales et nationales. En ce sens, les discriminations multiples sont un parfait exemple. Il s’agit de situations dans lesquelles interviennent et interagissent plusieurs motifs prohibés. Or, le concept de discriminations multiples, issu des sciences sociales, n’est théorisé en droit que depuis les années 1980. Si elles sont inconnues du droit positif, la doctrine et la pratique tendent à souligner la nécessité de leur reconnaissance juridique. Saisies par le droit du travail, elles posent de nombreuses questions quant à leur définition et leur mise en oeuvre. Leur étude va permettre de délivrer une approche différente de l’exigence de non-discrimination en droit du travail mais également des objectifs de diversité en entreprise. / Anti-discrimination law is always evolving. It must be receptive to new types of discrimination against workers to guarantee a level of legal protection consistent with international and national standards. In that sense, multiple discriminations are a perfect example. They take place when several protected characteristics occur and interact with each other. The concept of multiple discriminations arises from social sciences but has only been legally theorized since the 80s. If French law does not consider them, jurisprudence and practice tends to underline the necessity of a legal acknowledgment. Seized by employment law, multiple discriminations pose many questions with regard to their definition and implementation. Nonetheless, studying them offers a different approach to the duty to not discriminate at work, and to insuring diversity in the workplace.

This thesis addresses the question as to why multilevel politics is becoming an integral part of politics in Europe. Multilevel politics is conceptualized as a system which functions through a complex web of political relations within and across levels of decision making. The thesis argues that the rise of multilevel politics can be explained by its institutionalization in terms of the emergence, the evolution and especially the effects of relevant institutions. Based on a mixed-method research project, the influence of European institutions on subnational actors and the alignment of actor motives with institutional characteristics are empirically shown. The first chapter of the dissertation establishes the centrality of institutions for political transformation, examines the role of transnational and domestic institutions for multilevel politics, and contextualizes the research question in terms of institution-actor relations. The second chapter develops a new-institutionalist theoretical framework that explains the emergence, the evolution and the effects of the institutions, and formulates a series of hypotheses with regard to freestanding institutional influence, power distribution, material benefits and political identification. The third chapter outlines the mixed-method research design which addresses individual-level and institutional-level variations through a Europe-wide survey and a comparative case study. The fourth chapter on survey results shows generally favourable views on multilevel politics, and strong associations of these views with the independent variables under scrutiny. The fifth chapter specifies a multivariate model which includes all posited variables and confirms the majority of the hypotheses. Therefore, the new-institutionalist argument is broadly confirmed, while there is relatively weak evidence to sustain sociological explanations. The final chapter compares the Committee of the Regions and the Congress of Local and Regional Authorities, and examines the institutional characteristics which correspond to the hypothesized variables. It is then concluded that the two institutions share several overarching similarities, and display complementarity in other aspects.

Les révolutions de l’Est ont induit la fragmentation des Etats qui s’est accompagnée, sur le plan interne par une renaissance des partis ethniques ; ce qui ne va pas sans poser de problèmes à la démocratie politique. Les transitions et a fortiori les consolidations démocratiques font émerger un double phénomène d’interaction entre les acteurs et le système, dans la recherche d’un nouvel équilibre. Les partis ethniques se politisent alors que le système s’ouvre à l’acteur ethnique. On assiste donc à un réajustement évolutif du système devant la nouvelle donne. Le système s’ouvre aux nouvelles demandes à caractère ethnique de différentes façons et à différents degrés : entre la légalisation et la tolérance. Côté acteurs, les partis ethniques rentrent progressivement dans le jeu politique ; de différentes façons et à différents degrés. Dans notre champ problématique les relations interactives se déploient entre acteurs multi-niveaux (partis-Etats) et dans les divers champs (politique, sociétal et juridique). Leurs connexions sont croisées entre l’espace étatique et internationale, public et civil, politique et sociétal ; avec les Etats d’accueil ou d’origine, mais aussi, les Etats-tiers. Ils sont à velléités indépendantistes ou simplement des lobbies politiques. Nous avons essayé de mettre en lumière les principaux aspects de la complexité de la question ethnique dans les jeunes démocraties politiques ‘‘en consolidation’’. La problématique ethnique des PECO peut-elle nous aider à compléter en actualisant certaines visions généralistes des sciences politiques ? Les acteurs impliqués sont ainsi invités à éviter les pièges des nationalismes perçus comme ‘‘mesquins’’, voire ‘‘chaotiques’’ tout en servant la cause d’une plus souple intégration politique alias la ‘‘paix démocratique’’. / The revolutions of Eastern induced fragmentation of States were accompanied internally by a revival of ethnic parties, which is not without its problems in political democracy. Transitions and even more democratic consolidation are emerging a double phenomenon of interaction between actors and the system in search of a new equilibrium. Ethnic parties then politicize the system opens the ethnic actor. We are witnessing an evolutionary adjustment of the system to the new situation. The system opens to the new demands ethnic ways and to different degrees: between legalization and tolerance. Side actors, are gradually returning ethnic parties in the political game, in different ways and to different degrees. In our problem the field deploy interactive relationships between multi-level actors (parties-States) and in the various fields (political, societal and legal). Their connections are crossed between the State and international space, public and civil, political and social, with host countries or origin, but also the third States. They are separatist ambitions or simply political lobbies. We tried to highlight the main aspects of the complexity of the ethnic issue in young democracies political '' in consolidation ''. The ethnic problem of CEEC can help us to complete updating some general visions of political science? The actors involved are invited to avoid the pitfalls of nationalism perceived as '' petty '' or '' chaotic '' while serving the cause of a more flexible policy integration to the ‘‘democratic peace’’.