The Libyan crisis is the largest and closest crisis on the southern borders of the EU. It is therefore reasonable that the stabilization of this country and the engagement of international relations and partnership with an independent and effective government of Libya is a central point of the EU's foreign policy since the outbreak of the crisis in 2011. The consolidation of peace in Libya is of primary importance not only because of political and economic reasons. The engagement with Libya is essential for the EU even to strengthen its role as global actor in the field of foreign and security policy. Finally, the Libyan crisis is closely connected with the migration emergency that is weakening European political cohesion. The purpose of this article is thus to carry out a legal analysis on the role of the EU in promoting peace/state-building in Libya, to make some considerations on the main lesson learned. The Libyan crisis is the largest and closest crisis on the southern borders of the EU. It is therefore reasonable that the stabilization of this country and the engagement of international relations and partnership with an independent and effective government of Libya is a central point of the EU's foreign policy since the outbreak of the crisis in 2011. The consolidation of peace in Libya is of primary importance not only because of political and economic reasons. The engagement with Libya is essential for the EU even to strengthen its role as global actor in the field of foreign and security policy. Finally, the Libyan crisis is closely connected with the migration emergency that is weakening European political cohesion. The purpose of this article is thus to carry out a legal analysis on the role of the EU in promoting peace/state-building in Libya, to make some considerations on the main lesson learned.