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C-194/94. CIA brought proceedings against Signalson and Securitel (all parties were Belgian manufacturers of security equipment) for unfair trading practices. The defendants had published accusations that the claimant had failed to obtain appropriate approval for its products under Belgian law, a point which was not in dispute. However, the claimant argued that the Belgian national provision which made such approval necessary was in breach of an EC Directive that the Belgian government had failed to implement. Because the national provision was unlawful, argued the claimant, it was a breach of trading standards to accuse it of illegality for not having complied with it.

The ECJ held that the Belgian government should refrain from enforcing its national measure in preference to an EC Directive.

The significance of this decision is that, in all but name, the ECJ recognized horizontal direct effect in the case of a Directive, something that it had insisted, from Marshall v Southhampton and South West Area Health Authority No. 1 (1986) onwards, that it would not do. Although the ruling of the court was directed at the Belgian government, if this member state were to put the ruling into effect, the consequence would be that the claimant in the present case would be more likely to succeed in his action than he would otherwise be. This strategy (i.e. giving direct effect to a Directive in a dispute between private individuals by imposing a requirement on the state) has become known as 'incidental direct effect'. Its precise scope has not yet been fully determined.