The research conducted on this working paper focused on the best practices adopted at the European level to respond to populist threats to constitutional rules. The investigation, based on ten country reports involving national experts’ information, allowed the evaluation of the role of the constitutional judiciary and the impact of courts’ decisions-interpretations on the spread and on the counterreaction to populism. These pieces of empirical evidence allowed to identify three different types of methods and practices: (I) the “business-as-usual model”, in cases no changes in the jurisprudence occurred to react to populist threats (Austria, Italy, Romania, Czechia, United Kingdom); (II) the “changing interpretive practice to promote populist aspirations”, meaning those cases where populist issues triggered changes in interpretive practice resulting in a substantive concepts change and in some cases bringing real innovations into jurisprudence (Greece, Poland, Hungary); (III) the “changing interpretive practices to counteract populist initiatives” (Croatia). However, it should be noticed that in all cases populism did not generate any new theory of interpretation. Likewise, no close connection can be established between populist constitutionalism and methods of constitutional interpretation. In short, populists do not have preferrable interpretive patterns of theory or practice. Elements relating to populist constitutional drifts were grouped into four categories: (a) the preference of popular sovereignty and the promotion of direct democracy; (b) the claim for authentic representation and, together with this, the anti-pluralism; (c) an extreme approach of majoritarianism; (d) the restriction of certain fundamental rights together with intolerance/discrimination against certain minorities. The analysis proved that there are no national answers to “populist threats” that are effective everywhere, every time. However, some best practices are more dominant in the EU than others. Moreover, legal reactions to anti constitutionalist tendencies were examined on the basis of the Venice Commission opinions and the European Court of Human Rights decisions. Regarding the legal practices and practices of law in response to populism under the EU rule of law principle, the “EU Toolbox” – naming the set of legal tools and legal responses aiming to safeguard the EU Rule of Law – was examined theoretically and scrutinised in practice through case-law examination. The evaluation was assessed through the tailored “best practices” methodology: “efficiency”, “effectiveness” and “transferability” criteria.