The CSDP progressed rapidly from a reactive defence, typical of States, to a proactive design aiming at preventive defence. Efforts to make it more efficient and coherent resulted in competence delegation to non-elected bodies and in a tendency for pooling of resources and capabilities. National representatives in Brussels hold an indirect legitimacy; however, this policy’s strict intergovernmentalism has gradually been dissolving. Parliamentary scrutiny is uneven and National Parliaments can only oversee actions taken by their own governments, and thus cannot oversee the CSDP as a whole. Also, the European Parliament’s (EP) scrutiny powers are quite residual. As legitimacy is not an absolute concept and depends on perceptions, we interviewed stakeholders from the CSDP policy process. The latter produced a variety of definitions of legitimacy tout court and in the CSDP context. We found that the complexity of the legitimacy of the CSDP, marked by the interconnectedness of various layers of legitimacy, is often taken for granted by the decision-makers. Also, the low level of the popular awareness contradicts the challenge to the alleged ‘permissive consensus’. Finally, the legitimacy ideas shaped and endorsed by the CSDP stakeholders can bee seen as valid and meaningful empirical knowledge that reveals the importance of context and often refutes ideas defended by scholars.