Unlike different forms of authority from the EU such as Regulations, Directives cannot be used against private parties. If you would like to know why, read this answer.
hello, please advise. What is the reason why directives can’t be used horizontally ? Thank you
As confirmed in several judgments from the European Court of Justice (ECJ), European Directives are only capable of being used vertically and not horizontally. That is to say, that whilst an individual may rely on a directive in claiming against the state or a state body, they may not bring a claim against another private party on these grounds. This stands in contrast with the application of EU regulations, which may have vertical and horizontal direct effect, a distinction sometimes viewed as arbitrary(1). In the 1986 case of Marshall(2), which regarded an individual’s application against a public body, the ECJ stated directives were not horizontally applicable in an obiter sense, the subsequent case of Faccini Dori(3) in 1994, in which an individual attempted to bring a claim against a private business, saw this explicitly confirmed.
There are several reasons why it would be undesirable for directives to have horizontal effect. Perhaps most significantly, the phrasing of Directives is aimed at the state; it would be inappropriate to apply an obligation clearly intended for the State on to an individual. Further, prior to the 1992 Treaty, directives did not have to be published which raises the practical issue of whether it would be reasonably possible for an individual to have been aware of it. Whilst the justifications above are potentially rebuttable, and commentators question the logic of the distinction in effect of directives and regulations, it nonetheless seems an area unlikely to be changed anytime soon.
(1) P Craig and G de Burca, The Evolution of EU Law (2nd edn ,2011, OUP) 335.
(2) Marshall v South-Hampton & SW Hampshire Area Heath Authority (Case 152/84)  ECR 723.
(3) Faccini Dori v Recreb Srl (case C-91/92)  ECR I-3325.