This thesis analyses the security policy of the European Union and one of its member states. It aims at answering the question, whether internal and external security blurs in the EU, especially the differences between the two major security institutions - military and police. Using the concept of ideal types, an ideal type of a difference between the two bodies is introduced and subsequently tested on reality - on two case studies of the EU and the Czech Republic. There are three partial objectives: to find out if the roles of the military and the police blur at the level of the EU, if the European integration strengthens such blurring in the member states, and if the two bodies blur in a post-modern nation state. The thesis concludes that the real impact of declaratory changes is rather limited. Visible changes are caused by a subordination of external security concerns to prevention of internal ones. All changes are reversible easily, once the security discourse or political choices alter. The military and the police remain two distinct forces with different tasks and work methods.

La fin de la guerre froide, marquée par l'accord retrouvé des cinq grandes puissances membres permanents au Conseil de sécurité de l'ONU, au lieu de connaître un déclin dans les interventions militaires extérieures de celles-ci, a vu au contraire leur nombre se multiplier, ce qui portait atteinte à la règle générale, considérée comme une norme impérative (de jus cogens), celle de l'interdiction du recours à la force dans les relations internationales. Malgré les tentatives de justification des différentes interventions de grande envergure, menées au nom de la sécurité collective (interventions autorisées par le Conseil de sécurité) ou unilatéralement, celles-ci se sont écartées des prescriptions du droit international et de la Charte des Nations unies. En conséquence, elles s'avèrent à des degrés divers des actions entachées d'illégalité En effet, elles ont été fondées sur des interprétations extensives des dispositions de la Charte ou en violation de celles-ci, voire en violation des résolutions du Conseil de sécurité lui-même, ainsi qu'on peut le percevoir à travers les grandes interventions menées en Irak par les coalisés en 1991, celles de l'OTAN au Kosovo en 1999, des États-Unis en Afghanistan, à travers l'occupation américano-britannique de l'Irak en2003, l'intervention de la Russie en Géorgie (2008), de l'OTAN en Libye (2011) et celle de la France au Mali (2013). Cela n'a pas manqué de relancer le débat, récurrent dans les instances internationales concernées, sur la nécessité de réformer le Conseil de sécurité (élargissement de sa composition et règlementation du veto) ainsi que d'instituer un véritable contrôle de légalité sur ses actes. / The end of the cold war, marked by the agreement between the five major permanent member states of the United Nations Security Council, instead of a decline in their external military interventions, has, on the contrary, increased in number, which detracted from the general rule, considered as an imperative norm Qus cogens), that of the prohibition of the use of force in international relations. Despite the attempts to justify the various large-scale interventions carried out in the name of collective security (interventions authorized by the Security Council) or unilaterally, they have departed from the requirements of international law and the United Nations Charter. As a result, they appear to be in varying degrees to illegal actions. Indeed, they have been based on extensive interpretations of the Charter or on the breach of it or even in violation of the resolutions of the Council Security itself, as can be seen from the major interventions carried out in IRAK by the allies in 1991, those of NATO in KOSOVO in 1999, the US in AFGHANISTAN, through the US and British occupation of IRAQ in 2003, the intervention of Russia in GEORGIA (2008), NATO in LIBYA (2011) and that of FRANCE in MALI (2013). This did not fail to revive the debate, recurrent in the international bodies concerned, on the need to reform the Security Council (enlargement of its composition and regulation of the veto) as well as to establish a real contrai of legality on its acts.