National courts are the principal judicial enforcers of European law. ‘Ever since Van Gend en Loos the Court has maintained that it is the task of the national courts to protect the rights of individuals under [Union] law and to give full effect to [Union] law provisions.’ Indeed, whenever European law is directly effective, national courts must apply it; and wherever a Union norm comes into conflict with national law, each national court must disapply the latter. The Union legal order thereby insists that nothing within the national judicial system must prevent national courts from exercising their functions as ‘guardians’ of the European judicial order. In Simmenthal, the Court thus held that each national court must be able to disapply national law – even where the national judicial system traditionally reserves that power to a central constitutional court:
[E]very national court must, in a case within its jurisdiction, apply [Union] law in its entirety and protect rights which the latter confers on individuals and must accordingly set aside any provision of national law which may conflict with it, whether prior or subsequent to the [Union] rule. Accordingly any provision of a national legal system and any legislative, administrative or judicial practice which might impair the effectiveness of [European] law by withholding from the national court having jurisdiction to apply such law the power to do everything necessary at the moment of its application to set aside national legislative provisions which might prevent [Union] rules from having full force and effect are incompatible with those requirements which are the very essence of [Union] law.Functionally, the direct effect (and supremacy) of European law transform every single national court into a ‘European’ court. This decentralised system differs from the judicial system in the United States in which the application of federal law is principally left to ‘federal’ courts. Federal courts here apply federal law, while state courts apply state law. The European system, by contrast, is based on a philosophy of cooperative federalism: all national courts are entitled and obliged to apply European law to disputes before them. National courts are however not full European courts. Although they must interpret and apply European law, they are not empowered to annul a Union act. Within the Union legal order, this is an exclusive competence of the European Court:
Since Article [263] gives the Court exclusive jurisdiction to declare void an act of a [Union] institution, the coherence of the system requires that where the validity of a [Union] act is challenged before a national court the power to declare that act invalid must also be reserved to the Court of Justice.In opting for the decentralised judicial enforcement via state courts, the EU judicial system comes close to German judicial federalism; yet unlike the latter, state courts are not hierarchically subordinated. We saw in the previous chapter that there is no formal appeal procedure from the national to the European Courts, as the only procedural nexus here is the preliminary reference procedure. The relationship between national courts and the European Court is thus based on their voluntary cooperation. National courts are consequently only functionally – but not institutionally – Union courts (see Figure 11.1).

Has the Union therefore had to take State courts as it finds them? The Union legal order has indeed traditionally recognised the procedural autonomy of the judicial authorities of the Member States in the enforcement of European law:
Where national authorities are responsible for implementing [European law] it must be recognised that in principle this implementation takes place with due respect for the forms and procedures of national law.This formulation has become known as the principle of ‘national procedural autonomy’. It essentially means that in the judicial enforcement of European law, the Union ‘piggybacks’ on the national judicial systems. The danger of such ‘piggybacking’ is however that there may be situations in which there is a European right but no national remedy to enforce that right. But rights without remedies are like ‘pie in the sky’: a metaphysical meal. Each right should have its remedy(ies); and for that reason, the autonomy of national judicial procedures was never absolute. National procedural powers are thus not exclusive powers of the Member States; and the Union has expressly recognised that it can harmonise national procedural laws where ‘they are likely to distort or harm the functioning of the common market’.

But did this mean that, in the absence of positive harmonisation, the Member States were absolutely free to determine how individuals could enforce their European rights in national courts? The Court has answered this question negatively. The core duty governing the decentralised enforcement of European law is thereby rooted in Article 4(3) TEU: the duty of ‘sincere cooperation’. This general duty is today complemented by Article 19(1), which states: ‘Member States shall provide remedies sufficient to ensure effective legal protection in the fields covered by Union law.’
What does this mean? And to what extent does it limit the procedural autonomy of the Member States? This chapter explores these questions. We shall discuss two specific constitutional principles that the Court has derived from the general duty of sincere cooperation: the principle of equivalence and the principle of effectiveness. The classic expression of both can be found in Rewe:
[I]n the absence of [European] rules on this subject, it is for the domestic legal system of each Member State to designate the courts having jurisdiction and to determine the procedural conditions governing actions at law intended to ensure the protection of the rights which citizens have derived from the direct effect of [European] law, it being understood that such conditions cannot be less favourable than those relating to similar actions of a domestic nature … In the absence of such measures of harmonisation the right conferred by [European] law must [thus] be exercised before the national courts in accordance with the conditions laid down by national rules. The position would be different only if the [national rules] made it impossible in practice to exercise the rights which the national courts are obliged to protect.Even in the absence of European harmonisation, the procedural autonomy of the Member States was thus relative. National procedural rules could not make the enforcement of European rights less favourable than the enforcement of similar national rights. This prohibition of procedural discrimination was the principle of equivalence. But national procedural rules – even if not discriminatory – ought also not to make the enforcement of European rights ‘impossible in practice’. This would become known as the principle of effectiveness. Both principles have led to a significant judicial harmonisation of national procedural laws, and this chapter analyses their evolution in sections 1 and 2 below.

Section 3 turns to a third – famous – incursion into the procedural autonomy of national courts: the liability principle. While the previous two principles relied on the existence of national remedies for the enforcement of European law, this principle establishes a European remedy for proceedings in national courts. An individual can here, under certain conditions, claim compensatory damages resulting from a breach of European law. Importantly, the remedial competence of national courts is confined to national wrongs. They cannot give judgments on the non-contractual liability of the European Union. For the latter power is – like the power to annul Union law – an exclusive power of the Court of Justice of the European Union.

Having analysed the three major constitutional principles governing the decentralised enforcement of European law ‘in the absence of harmonisation’, section 4 finally explores what happens in areas in which the Union has harmonised the remedial or jurisdictional competences of national courts. The most significant harmonisation here relates to the jurisdictional competences of national courts. This has allowed the Union to generally give national judgments transnational effects within the Union legal order. When, for example, will a judgment issued by a French or German court bind the judiciary in the United Kingdom? The most important Union harmonisation here relates to civil law but similar moves have been made in the context of criminal law.