Abstract The present contribution supports the contention that general principles of EU law do not operate as an unstoppable centripetal force at the service of an activist judiciary. Quite the contrary, when having recourse to general principles, the ECJ strives to preserve the vertical and horizontal allocation of powers sought by the authors of the Treaties. Horizontally, the ECJ distinguishes between matters pertaining to the province of constitutional law and those which are subject to legislative discretion. Stated differently, general principles of EU law are applied without encroaching upon the competence of the EU legislature. Vertically, the ECJ is respectful of the constitutional traditions of the Member States but not to the extent of foregoing the basic constitutional tenets of the Union. General principles seek to create a ''common constitutional space'' where EU and national law engage in a dynamic dialogue which gives rise to a mutual influence between the two levels of governance. Hence, as instruments of constitutional dialogue, general principles facilitate the constant renewal of the EU legal order, epitomising the ''EU's living constitution''. The article examines the horizontal direct effect of general principles, paying attention to the gap-filling function of general principles, and their role in consistent interpretation and as grounds for review, in a situation of constitutional pluralism.