This project concerns the way the European Union (EU) can build an area of freedom, security and justice by making use of its powers to enter into international agreements with third countries. The EU has recently acquired the competence to legislate in this area. Very recently, the European Council has put forward the idea that the EU internal action is not enough to build such an area. Challenges to the EU external borders such as illegal immigration and threatens to the EU internal security such as terrorist attacks and organised crime (money laundering, trafficking of human beings, drugs) require the EU to act as an international actor. This is why the EU has started to make use of a wide range of international agreements, affecting cross pillar policies, whose adoption involves various actors such as the Commission, the Council, Europol. The objective of this project is to identify possible legal problems that the European Institutions may face in concluding these agreements. More precisely, the following legal issues will be explored: a) to what extent international agreements are necessary as well as effective to build an area of freedom, security and justice; b) whether the EU is competent to enter into these agreements affecting an ever increasing number of cross pillar policies and to what extent Member States remain competent to conclude international agreements in areas affecting the EU internal security and the EU external borders; c) whether these agreements are coherent; d) whether these agreements create accountability problems, in particular as far as the Europol’s agreements are concerned. This project is in line with the objectives of the Work Programme for experienced researcher since it is intended to expand the applicant’s competences in a new area of research and is based on a multidisciplinarity approach. This proposed shift of research interests will enable the applicant to strengthen her chances of being appointed Professor.