The basic principle of sincere cooperation in the law of the European Union

Although it is somewhat wider in scope by its character than the other basic principles that regulate the relationship between the law of the European Union and the domestic law of Member States, the principle of loyal or, according to the Lisbon solutions, "sincere" cooperation represents one of central definitive and developmental building elements on which the legal order of this European organization rests. Thus, the focus of this article is the notion and definition of this principle, its genesis, as well as the scope of its application in relation to directives as formal sources of EU law; the positions held by the Court of Justice of the European Union contributed the most to this analysis. The research utilized analytical and synthetical methods, with content analysis and historical-comparative analysis taking the centre stage. The article ends with concluding remarks, where the most interesting ones are those that contribute to the argument that the principle of sincere cooperation belongs to the category of tools via which national difference could be lessened in order to achieve the goals of the European organization and that the presupposition for this to happen is, among other factors, to remove the malformations that exist in the relationship between the principle of sincere cooperation and the directive as a source of secondary law of the European Union.