The contribution aims at assessing the role and scope of the rule of law in the EU legal order before and after the entry into force of the Lisbon Treaty. The investigation will consider both the internal and external dimensions of the principle with a view to appraise the current state of the art in terms of the applicable legal framework, single out its main criticalities, and review future perspectives for its affirmation and promotion The rule of law acts as a fundamental value for the institutions and the Member States. It operates as a parameter of legality of EU acts and as a guiding principle, but it also represents an important leverage in terms of political pressure, both within and outside the Union. On these premises, the remainder of this contribution is structured as follows. Firstly, the relevant legal framework is examined in light of the applicable case law. Secondly, the attention focuses on the protection of the rule of law when there is a clear risk of a serious breach by a Member State. Thirdly, the main instruments for the promotion of the rule of law in the context of the EU‟s external action are reviewed in order to assess the true potential of the principle in this area. Lastly, some final remarks summarize the current shortcomings and outline future perspectives for the protection and promotion of the rule of law in and outside the Union.