The Treaty of Lisbon has significantly enhanced the EU’s institutional framework and the instruments at its disposal in foreign policy and external relations, notably through the creation of the function of the High Representative, supported by the European External Action Service. Contributing to the maintenance of international peace and security is one of the core objectives of the EU’s external action. This volume, with contributions from legal experts on EU foreign policy and external relations, illustrates the manifold legal issues arising in EU external action and in its efforts to achieve this essential objective.