The paper focuses first on the concept of “rule of law” and its requirements. The legislative framework of the European Union on the conditionality mechanism on the rule of law is analyzed in detail. The last part of the exposition concerns the effective application of the legislation ensuring the protection of the European budget in case of violation of the principles of the rule of law by a Member State. In this regard, some judgments of the Court of Justice of the European Union are commented on, given by it in a few cases involving Hungary and Poland, on the one hand, and the European Parliament and the Council of the European Union, on the other part. The purpose of this article is to highlight the complexity and the very special importance of the concept of the rule of law, essential value expressis verb is consecrated, to analyze the specific legislation in the field existing at the level of the European Union. Finally, the shortcomings of the Member States in respecting the principle examined are highlighted; in this respect, several judgments of the Court of Justice concerning systematic infringements of the rule of law by some Member States of the European Union are analyzed. The historical and the comparative methods are used in this presentation. The article is of particular importance to the European Union, to the experts in the field, but especially to the Member States of the European Union, which have undertaken to take over and give priority to its specific legislation by joining this regional organization. Although Poland and Hungary have been convicted for the systematic violations of the rule of law, they have not remedied their situation, despite the sanctions applied.