The rule of law has become a hotly debated issue at EU level recently. What appears to be missing in those debates, however, is attention to the peculiarities the rule of law presents in the setup of the EU’s economic constitutional framework. The founding EU Treaties have put in place such framework permitting Member States’ diversified (capitalist) economies to grow ever closer. At the same time, however, that framework has also continuously given rise to specific rule of law challenges. This diagnostic article revisits and summarizes those challenges, arguing that addressing them is more than ever necessary if only to increase the EU’s legitimacy in targeting more general rule of law deficiencies in some of its own Member States.