<P> That task also falls to national courts, in as much as they retain jurisdiction to review the administrative implementation of Union law, for which the authorities of the Member States are essentially responsible; many provisions of the Treaties and of secondary legislation--regulations, directives and decisions--directly confer individual rights on nationals of Member States, which national courts must uphold . </P> <P> National courts are thus by their nature the first guarantors of Union law . To ensure the effective and uniform application of Union legislation and to prevent divergent interpretations, national courts may, and sometimes must, turn to the Court of Justice and ask that it clarify a point concerning the interpretation of Union law, in order, for example, to ascertain whether their national legislation complies with that law . Petitions to the Court of Justice for a preliminary ruling are described in Article 267 (ex Article 234) of the Treaty on the Functioning of the European Union . </P> <P> A reference for a preliminary ruling may also seek review of the legality of an act of Union law . The Court of Justice's reply is not merely an opinion, but takes the form of a judgment or a reasoned order . The national court to which that is addressed is bound by the interpretation given . The Court's judgment also binds other national courts before which a problem of the same nature is raised . </P> <P> Although such a reference may be made only by a national court, which alone has the power to decide that it is appropriate do so, all the parties involved--that is to say, the Member States, the parties in the proceedings before national courts and, in particular, the Commission--may take part in proceedings before the Court of Justice . In this way, a number of important principles of Union law have been laid down in preliminary rulings, sometimes in answer to questions referred by national courts of first instance . </P>

Court of justice of the european union judges