The horizontal direct effect of Directives is a contentious issue. Numerous Advocates General have supported the case for establishing horizontal direct effect. However, the ECJ has always resisted a change of the "Marshall" case law as to allow a general right to invoke on unimplemented directives against private parties. In a number of cases the ECJ has established means for limiting the scope of the prohibition of horizontal direct effect, and ensure the full effectiveness of directives as much as possible.