This thesis investigates competition law, State aid law and free-movement law in their interaction with Article 11 TFEU’s obligation to integrate environmental protection requirements into all activities and policies of the Union. The Article is formulated in broad and sweeping terms which makes integrating environmental protection requirements complex and context-dependent. The challenge of integrating environmental considerations is further increased as such integration in competition, State aid and free- movement law is different from other areas of EU action. The three areas are the core provisions protecting the internal market by prohibiting certain actions of the Member States and undertakings. Unlike in other areas, the EU is therefore not in the position to develop or design the actions but has to scrutinise the measure according to pre-established parameters. To address this challenge, a novel functional approach to environmental integration is developed. The approach should facilitate a better understanding of environmental integration and in particular its application to competition law, State aid and free-movement law. An important element of this thesis equally the comparison between the three areas of law. It sheds light on conceptual issues that are not only relevant to the integration of environmental protection. The comparison advances the understanding in relation to questions such as how restrictions are defined and how the respective balancing tests are applied. The contribution of this research is therefore twofold. One the one hand, it compares how the different tests in competition, State aid and free-movement law operate, thereby offering opportunities for cross-fertilisation. On the other hand, this comparison and the improvements suggested as a result help to conceptualise environmental integration thereby paving the way for a more transparent and consistent integration of environmental protection in competition, State aid and free-movement law.

L’existence d’une multiplicité de figures juridiques de la concurrence pourrait conduire à un manque de cohérence et d’intelligibilité du régime européen de la concurrence. Ce dernier canalise d’ailleurs une partie des critiques relative au déclin du droit. Toutefois, l’étude de ses multiples traductions juridiques aboutit à un constat bien différent. Derrière un apparent désordre, l’approche européenne de la concurrence fait preuve d’une profonde cohérence. Dans chacune des figures juridiques de la concurrence, un même objectif officie au titre de standard. Il s’agit de la loyauté de la concurrence. Cette dernière intervient dans l’ensemble des régimes européens de la concurrence comme une notion autour de laquelle gravite un ensemble de solutions cohérentes par leur finalité et leur contenu. Cohérentes par leur finalité, tout d’abord, car les multiples traductions de l’ordre concurrentiel européen abordent la loyauté de la concurrence comme un moyen de protéger le bon fonctionnement du marché concurrentiel. Cohérentes par leur contenu, ensuite, car chacune des figures juridiques de la concurrence vise à assurer la loyauté de la concurrence en préservant l’égalité des chances entre les opérateurs économiques. De fait, le constat de la transversalité et de l’homogénéité de traitement de la loyauté de la concurrence révèle que l’objectif a, jusqu’alors, été largement sous-estimé. Cette mise à l’écart est regrettable car, en raison de sa neutralité axiologique, l’introduire dans les différents débats relatifs à l’approche européenne de la concurrence offre de véritables solutions en termes d’homogénéisation de la notion de concurrence et de meilleure intégration des figures juridiques de la concurrence. / The existence of various rules regarding competition could lead to a lack of coherence andintelligibility of the European system of competition. As a matter of fact, the latter channels a part of the criticisms relating to the decline of law. However, the study of its numerous legal translations results in a very different conclusion. Behind an apparent disorder, the European approach to competition shows profound coherence. In each legal aspects of competition, a common objective officiates as a standard. It is the fair competition. The latter intervenes in all European competition regulations as a notion around which revolve a set of solutions coherent by their finality and content.Coherent by their finality, firstly, because all the legal translations of the competitive order address fair competition as a way to protect competition and, more generally, public interest.Coherent by their content, secondly, because each legal aspects of competition ensures faircompetition by preserving the equality of opportunity between competitors.De facto, the observation of the transversality and homogeneity of the treatment of fair competition reveals that the objective has been, until now, widely underestimated. This sidelining is regrettable because, on the grounds of its axiological neutrality, introducing it into the different debates relating to the European approach to competition offers real solutions in terms of the homogenization of the notion of competition and better integration of the legal aspects of competition.