Within the jurisdiction of the E.C.J. it is also the issuing of preliminary rulings, which constitutes the most frequent and important task of this Court. The preliminary ruling procedure takes place after a national court refers a preliminary question when in doubt as to how to interpret and/or apply the European Union legislation during the hearing of a case before it. The ruling issued by the E.C.J. does not concern the substance of a case but only the preliminary question of legal nature. The ruling is binding to all member-states and must be applied uniformly. In this way it is ensured that the European Union legislation is correctly applied without the risk of being given different interpretations by national courts.
Preliminary Rulings have, also, been issued in relation to the European Union Labour legislation and can be found in the following websites: www.curia.europa.eu or/and www.eur-lex.europa.eu.