A national court asked whether it had the power to declare a Commission decision invalid on grounds that it contradicted an EC regulation.
ECJ said that national courts do not have the power to declare void community acts.
National courts may dismiss arguments that a community decision is void if the claims to that effect are unfounded, but cant find invalidity itself without a reference.
To allow this would be to allow the community law to be applied inconsistently.
Uniformity is particularly in question where it is the validity (rather than interpretation which is in question).
ECJ has exclusive jurisdiction in this respect.