In the last decade, EU integration has been marked by a number of existential crises that challenge its constitutional structures and touch upon the founding values of the Union as set out in Article 2 TEU. Among them, a value that has served as the cornerstone of European integration seems particularly threatened: the Rule of Law. The Rule of Law crisis has many facets. On some occasions, it is due to undue extensions of governmental power, such as in cases of interference with the judiciary or restrictions of media freedom, civil society organisations and academia (Poland, Hungary). In other cases, the Rule of Law is threatened by endemic corruption (Romania, Bulgaria) or weak institutional capacities (Greece). This project mainly focuses on Member States that present so grave deficiencies in guaranteeing the Rule of Law that their conformity with basic EU standards is seriously questioned. Although it is obvious that the EU cannot stay inactive in the face of such deficiencies, it remains unclear how potential responses fit with the overall EU constitutional framework. This project contributes to this discussion by developing the concept of "systemic deficiency" in the Rule of Law and also by critically observing the ongoing efforts to advance appropriate EU instruments to address the diverse challenges to the rule of law.