An important tool in the EU legal toolbox to maintain legal certainty and uniform application of EU law is the possibility for national courts to ask the European Court of Justice for a preliminary ruling. This is usually done when a question of interpretation of EU law arises before a national court of last instance and that court considers that an ECJ decision on this question is necessary to produce a judgment in the case before it. In fact, in such cases the judge of the court is obliged to send a reference to the ECJ. But what about the lower courts, can they also send reference to the ECJ?