This article investigates some special criteria of implementation of the EU directives into the national legal order and the consequences of their non-compliance, that could arise from the EU membership obligation to the European Union law. The most important acting form for the Institutions of European Union comes after the Reform treaty of Lisbon the form of the EU directive. The law-making practice of the Institution of the European Union set out with different levels of full or partial harmonization of (...) the EU directives. Consequently, there comes the problem of the enforcement of the adopted EU directives into the domestic legal order. The article analyses the changes in European Union law after the Reform of Lisbon. The investigation begins with treatment of the general characteristic of the EU directive. After that it analyses the choice of primary legal ground for adopting of the EU directive and the consequences of its wrong choice for the legality of the EU directive. (shrink)