Article 23 of the Treaty on the Functioning of the European Union (TFEU) provides for the right of EU citizens to diplomatic and consular protection by Member States other than the State of nationality in the territory of a third country. But what are the concepts of diplomatic and consular protection embodied in that Article? Are those typical of public international law or rather novel concepts with autonomous meaning derived from EU law? This paper addresses this question and examines what are possible effects of Article 23 in terms of opposability of the concept of EU citizenship to third states as well as in terms of justiciability of the EU citizen’s right to obtain protection from a non national Member State in a third country. The paper concludes that political and legal practice of the EU and of Member States has yet to provide clear answers to these questions.