Indirect effect is a principle of the European Union (EU) law, whereby national courts of the member states of the EU are required to interpret national law in line with provisions of EU law.
The principle of indirect effect contrasts with the principle of direct effect, which, under certain conditions, allows individuals to invoke the EU law itself before national courts.
[1] While Von Colson dealt with a situation where a member state had failed to implement a directive correctly, in Marleasing v La Comercial Internacional de Alimentacion the ECJ extended indirect effect to situations where the member state concerned had not implemented the directive at all.
Recommendations and opinions have no binding force, like directives have.
However, in Grimaldi v Fonds des Maladies Professionnelles the ECJ has ruled that since recommendations and opinions must have some legal effect, they should be taken into consideration when dealing with measures that the two were supposed to supplement.