The article identifies the reasons which moved the Czech Constitutional Court to declare the judgment of the European Court of Justice in C-399/09 Larultovd concerning the application of social security schemes in unprecedented way as an ultra vires act and to deprive it of binding force within the domestic legal system. The author argues that a more express ECJ's pronouncement about persons discriminated contrary to the respective EC Regulation, its more careful understanding of what exactly the Czech Court's case law was saying and - in particular - a reference by the Czech Court for preliminary ruling concerning the interpretation of the EC Regulation could avoid the unfortunate outcome of the case.
The limitation of Member States's sovereignty by the European integration requires to make lines between the scope of competences conferred on the EU and the national ones also in the area of judicial power more transparent. This is what the article tries to do: to review the national reservations towards primacy of EU law as questionable, if their justification has not been cleared before by the ECJ.