Justifications of the EU's foreign policy have two addressees: the first is internal to the EU and consists of the member states and their citizens; the second is external and consists of non-member states and their citizens. This chapter focuses on the EU's attempts to validate its foreign policy externally. It considers the EU's policy on enlargement as foreign policy. The chapter presents analytically distinct approaches for examining the basis of legitimacy for foreign policy in general. There are three analytically distinct ways in which a foreign policy can achieve legitimacy. They are grounded in different logics of action or justification for an individual actor: a logic of consequences, a logic of appropriateness and a logic of moral justification. The chapter analyses how the EU has actually applied membership conditionality and how it has justified its actions.