The thesis addresses the puzzle of the differential integration of former communist states in the Euro-Atlantic community of nations between 1989 and 2000. Notwithstanding the predominant universalist-rationalist assumption that the adoption of an institutional-administrative blueprint for reform could lead to convergence between East and West, countries such as Poland, Bulgaria and Russia did not converge similarly (or at all) on the West European normative model and framework of international relations. To account for this divergence, the thesis examines the impact of the culturally-historically informed, Polish, Bulgarian and Russian identities and conceptions of 'Europe' (as opposed to the formal-institutional transition from one system to another) on the process of foreign policy transformation. The doctoral research employs Constructivism, Social Psychological insights and an interpretivist methodology, drawing on 75 elite interviews. The main argument states that differential Europeanisation can be understood on the basis of differentiated levels of inclusion and establishment of relations of mutual recognition and belongingness - substantiated by a differentiated extent of ideational affinity (i.e., normative compatibility), which are (re)enacted in the interactive, mutually constitutive process of identification between Self and Other (i.e., between Poland, Bulgaria and Russia and (Western) Europe). Three propositions of 'thick', 'ambivalent' and 'thin' Europeanisation are derived from the argument (whereby the comparative benchmark of Europeanisation is an ideal-typical model of European-ness). Key contributions focus on the development of a refined Constructivist theory and a systematic empirical comparison of Polish, Bulgarian and Russian foreign policy identities. Also, the study's conclusions reinvigorate and reconfirm the importance of the continuity (rather than just constant flux) of culturally-historically shaped patterns of group self-understandings and sub-regional identifications as well as Constructivism's greater plausibility in accounting for the research puzzle than (Neoclassical) Realism through the stipulation of a mutually constitutive relationship between international and domestic factors and between ideational and interest-based considerations.

L’Union européenne (UE) se sert principalement d’outils normatifs pour exercer du pouvoir sur la scène internationale, notamment par la promotion de ses propres lois et standards. Le meilleur exemple est l’élargissement de l’UE, processus ayant contribué à stabiliser l'Europe et à transformer les candidats en des démocraties de marché, notamment en promouvant un rapprochement avec les normes européennes en échange d’une perspective d’adhésion à l’UE. La Politique européenne de Voisinage (PEV) utilise les mêmes mécanismes développés lors des élargissements, notamment la promotion de réformes en échange d’incitatifs financiers. Par contre, la PEV n’offre aucune perspective d’adhésion à l’UE aux États qui y participent. Ainsi, plusieurs études ont conclu que cette politique ne pourrait engendrer les réformes escomptées. Bien que la coopération au sein de la PEV ne soit pas aussi fructueuse que lors des élargissements, on remarque que certains pays plus que d’autres ont, malgré l’absence de perspective d’adhésion, fait des changements à leur législation en conformité avec les normes européennes. En comparant la coopération dans le secteur de la Justice et des affaires intérieures en Moldavie et en Ukraine, nous montrons que la différence s’explique par l’importance des facteurs internes des pays concernés, notamment l’existence d’identités nationales contestées et les batailles politiques intérieures portant sur la politique étrangère. / The European Union (EU) relies heavily on normative tools to exert power in world politics, such as the promotion of its own laws and standards. The most successful case is the EU enlargement process, which has contributed to stabilize the vicinity and transform candidates into market-based democracies by promoting alignment with European legislation and offering the prospect of EU accession. The European Neighbourhood Policy (ENP) uses the same mechanisms that have made enlargement a successful policy, notably incentives-fueled reform. It does not however offer participating states a membership perspective and therefore most scholarly studies have drawn bleak prospects on its ability to promote reform. While cooperation in the ENP framework is not as intense as during the enlargement rounds, we find that some countries have indeed been making changes to their legislation and aligning themselves with the acquis communautaire, while other countries have not been so successful. By comparing norm implementation in the field of Justice and Home Affairs in the cases of Moldova and Ukraine, we show that differences are explained by the significant impact of domestic factors, such as contested state identities and domestic political battles over foreign policy.

L’Union européenne (UE) se sert principalement d’outils normatifs pour exercer du pouvoir sur la scène internationale, notamment par la promotion de ses propres lois et standards. Le meilleur exemple est l’élargissement de l’UE, processus ayant contribué à stabiliser l'Europe et à transformer les candidats en des démocraties de marché, notamment en promouvant un rapprochement avec les normes européennes en échange d’une perspective d’adhésion à l’UE. La Politique européenne de Voisinage (PEV) utilise les mêmes mécanismes développés lors des élargissements, notamment la promotion de réformes en échange d’incitatifs financiers. Par contre, la PEV n’offre aucune perspective d’adhésion à l’UE aux États qui y participent. Ainsi, plusieurs études ont conclu que cette politique ne pourrait engendrer les réformes escomptées. Bien que la coopération au sein de la PEV ne soit pas aussi fructueuse que lors des élargissements, on remarque que certains pays plus que d’autres ont, malgré l’absence de perspective d’adhésion, fait des changements à leur législation en conformité avec les normes européennes. En comparant la coopération dans le secteur de la Justice et des affaires intérieures en Moldavie et en Ukraine, nous montrons que la différence s’explique par l’importance des facteurs internes des pays concernés, notamment l’existence d’identités nationales contestées et les batailles politiques intérieures portant sur la politique étrangère. / The European Union (EU) relies heavily on normative tools to exert power in world politics, such as the promotion of its own laws and standards. The most successful case is the EU enlargement process, which has contributed to stabilize the vicinity and transform candidates into market-based democracies by promoting alignment with European legislation and offering the prospect of EU accession. The European Neighbourhood Policy (ENP) uses the same mechanisms that have made enlargement a successful policy, notably incentives-fueled reform. It does not however offer participating states a membership perspective and therefore most scholarly studies have drawn bleak prospects on its ability to promote reform. While cooperation in the ENP framework is not as intense as during the enlargement rounds, we find that some countries have indeed been making changes to their legislation and aligning themselves with the acquis communautaire, while other countries have not been so successful. By comparing norm implementation in the field of Justice and Home Affairs in the cases of Moldova and Ukraine, we show that differences are explained by the significant impact of domestic factors, such as contested state identities and domestic political battles over foreign policy.