European Union Law and National Law: A Common Legal System?

Abstract

EU law and the national laws of the EU Member States are closely interwoven. From a historical point of view, they form two different legal orders, but they may today be viewed as forming part of the same legal system. The chapter explains the relationship between EU law and national law by looking first at the status of EU law in national law and then at the relevance of national law to EU law. The status and impact of EU law in domestic legal systems have already received a great deal of attention in the legal doctrine, and the chapter therefore particularly focuses on the second aspect, which has to date received far less attention. The role domestic laws play at the EU level is examined here by looking at the different functions that Member State national laws have in an EU law context by examining the relevance of national material (substantive) and procedural and institutional laws at the EU level. This chapter concludes that the relationship between EU law and domestic laws is fundamentally different from the traditional dichotomy between public international law and domestic law. Member State national laws have directly impacted, and continue to impact, the substance of EU law. Furthermore, the way in which EU law instrumentalises domestic laws—in particular domestic institutional law—for its own purposes and harnesses national administrative bodies to the same end suggests that EU law and national law are best understood as forming a single complex system of multi-level governance.

1 Introduction

The European Union (EU) is a constitutional ‘federative’ order rather than an intergovernmental organisation.¹ The objectives, tasks and competencies of the Union span over an ever-broadening field, albeit under the direction of the principle of conferral.² Its constitutional order is endowed with an elaborate internal hierarchy of norms³ as well as institutions empowered to adopt, in most cases by a majority voting, legislative and regulatory acts. At the same time, this constitutional order determines the status of Union norms in the national legal orders of its Member States.⁴ The duty to ensure that the hierarchy of norms is respected, as well as the rules governing the relationship between Union law and national law, is entrusted above all to an independent judicial system, consisting of two Union courts⁵ and the national courts of the Member States.⁶

These are the premises on which the present contribution is built. The following discussion will have a more limited focus, however. My aim is to consider the relationship between Union law and national law by looking first at the status of Union law in national law and then at the relevance of national law to Union law. The first aspect is a well-known characteristic of the EU legal system, and it has already received much attention in the legal doctrine. I will limit myself to a summary of the most salient features. The second aspect has received much less attention so far. It will be examined here by looking at the different functions that the national laws of the Member States may have in a Union law context by considering the relevance of national material (substantive) and procedural and institutional laws. The use, for Union law purposes, of national institutional law in particular, implying that national administrative and other bodies are to a greater or lesser degree instrumentalised with a view to carrying out the Union’s tasks, supports the view that the EU is a complex system of multi-level governance.⁷

Public international law does not generally form part of national law unless such an effect is recognised in the national legal order. In other words, and as a general supposition,⁸ public international law does not prohibit states from adopting a dualist approach to the question of the relationship between public international law and domestic law.⁹ EU law is a different animal since, as stated by the European Court of Justice (ECJ), the founding treaties of the Union, ‘unlike ordinary international treaties, established a new legal order, possessing its own institutions, for the benefit of which the States have limited their sovereign rights, in ever wider fields, and the subjects of which comprise not only Member States but also their nationals’.¹⁰ EU law is characterised by the fact that it ‘stems from an independent source of law, the Treaties, by its primacy over the laws of the Member States … and by the direct effect of a whole series of provisions which are applicable to their nationals and to the Member States themselves’…¹¹

If one adds to these characterisations the various functions that national law may have in Union law (as will be elaborated upon below), it becomes obvious that there is such a close link between Union law and national law that the relationship between the two differs significantly from the traditional dichotomy between public international law and domestic law. The latter relationship seems more apt to describe the relationship between public international law and Union law (Union law then performing the role of domestic law). It is true that the ECJ has referred to the ‘autonomy’ enjoyed by Union law in relation not only to international law but also to the laws of the Member States.¹² The Court also has, on numerous occasions, referred to the ‘procedural autonomy’ of the Member States.¹³ The question, then, arises whether the notion of autonomy should be maintained when analysing the relationship between Union law and national law or whether this relationship should be rather linked to the idea of EU law and national law forming a common legal system.¹⁴ To the extent that they could be considered as forming a common legal system, the question also arises whether such a characterisation would fly in the face of the fact that the Union consists of 27 Member States, which can be said to have each their own national legal order, which may differ considerably from the other national orders. An effort to answer these questions will be made in the concluding section.

2 Union Law as Part of National Law

The founding Community treaties, which established the European Coal and Steel Community (1951), the European Economic Community (EEC 1957) and the European Atomic Energy Community (Euratom 1957), while being based on the idea of supranationalism, were rather poor in explaining what status Community law was meant to have in the national legal orders of the six Member States. This task was left to the ECJ, which clarified the foundations of the Community legal order and its relationship with national law in the seminal judgments of Van Gend & Loos and Costa v ENEL.¹⁵ It is interesting to note that in Van Gend & Loos, one of the arguments of Advocate General Roemer in rejecting the thesis of the direct effect of then Article 12 EEC was that if this provision was deemed to have a direct internal effect, ‘breaches of Article 12 would render the national customs law ineffective and inapplicable in only a certain number of Member States’.¹⁶ This was so because the Advocate General assumed that even if there was a direct effect, the national constitution (he mentioned Belgium, Italy and Germany) would seem to be based on the lex posterior rather than the lex superior principle when it came to the question of the relationship between international treaties and domestic law. He, in other words, considered that the EEC Treaty was to be seen as any international treaty and could not prevail over national law if the national rule in question was of a later date (lex posterior).

The answer of the ECJ was to make a clear distinction between international agreements in general and the EEC Treaty, the latter constituting ‘a new legal order of international law’, and to affirm, one year later in Costa v ENEL, that the law stemming from the Treaty was ‘an independent source of law’, which because of its ‘special and original nature’, could not be overridden by domestic legal provisions, ‘however framed’. In contrast to ‘ordinary international treaties’, the EEC Treaty had created ‘its own legal system which, on the entry into force of the Treaty, became an integral part of the legal systems of the Member States’. As these clear and strong assertions of both direct effect and primacy created a problem with regard to ensuring respect for fundamental rights, these rights being recognised in national constitutions but not in Community law, the ECJ in Stauder held for the first time that fundamental rights formed part of the general principles of Community law.¹⁷

The emerging constitutional order thus implied that Community rules, which prevailed over national rules, became applicable also at the national level and could in many cases be directly invoked before national courts and authorities and that they consisted of not only written rules of primary (the basic Treaties with Protocols) and secondary (regulations, directives and decisions) law but also general principles of Community law, including fundamental rights.¹⁸ There is no need here to recall the subsequently and extensively written primary and secondary laws, as well as the case law confirming and developing these features of the constitutional order. The direct applicability of Union law and the direct effect of many treaty provisions, regulations and, on certain conditions, directives and decisions have become a generally recognised attribute of the Union legal order.¹⁹ Fundamental rights have been recognised, at a general level, in the basic Treaties and regulated in more detail in the EU Charter of Fundamental Rights.²⁰ The principle of the primacy of Union law over the laws of the Member States, and their constitutional law in particular, has been confirmed, over and over again, in ECJ case law,²¹ including case law that leaves it to the ECJ to be the final arbiter of the validity of Union legal acts.²² At the political level, a Declaration annexed to the Final Act of the Intergovernmental Conference, which adopted the Lisbon Treaty, contains an unconditional reaffirmation of the principle of primacy.²³

That said, there is some national case law, especially of national constitutional courts, that seems to call into question, or at least assert some limits to, the principle of primacy.²⁴ This line of case law is usually based on the idea that by virtue of the principle of conferral and the national rules governing accession to the EU, the national courts may control whether certain actions by the Union, including the Union courts, go beyond what has been conferred (ultra vires).²⁵ Tensions and even conflicts between national and ECJ case law may arise in situations involving the principle of primacy, the direct effect of Union law and fundamental rights. An example is provided by the Danish Supreme Court’s judgment in Ajos, holding that despite Article 6(1) and (3) of the Treaty on European Union (TEU), the provisions of the EU Charter of Fundamental Rights and the general principles mentioned in Article 6(3) have not been made directly applicable in Denmark.²⁶ This view appears to be based on the assumption that the question as to whether a direct effect exists should be judged on the basis of Danish law, a view that obviously cannot be reconciled with the ECJ case law since the judgments in Van Gend & Loos and Costa v ENEL. It is to be noted, however, that the Ajos case concerned not the principle of primacy in general but the alleged direct effect of fundamental rights (discrimination on the basis of age) in a horizontal situation, that is, litigation between private parties and, thus, a question that is still open to debate also at the Union level.²⁷

Another example of a possible tension between national and ECJ case law is offered by the decision of the Italian Constitutional Court, in what has been referred to as the Taricco Saga,²⁸ to ask the ECJ to clarify the meaning of its Taricco I judgment (concerning national limitation rules in the context of criminal proceedings).²⁹ The Constitutional Court implied that a given interpretation of the consequences arising from the application of Article 325 of the Treaty on the Functioning of the European Union (TFEU) (combatting illegal activities affecting the financial interests of the Union) could lead the Constitutional Court to consider that the interpretation was incompatible with some overriding principles of the Italian constitutional order, in this case the principle of legality.³⁰ This request for a preliminary ruling led the ECJ to adjust its earlier judgment, stating that in the context as outlined by the Constitutional Court, there was not necessarily an obligation to disapply certain national provisions relating to limitation periods in the context of criminal proceedings.³¹ There was no such obligation if the disapplication of the national provisions would entail a breach of the principle that offences and penalties must be defined by law because of the lack of precision of the applicable law or because of the retroactive application of legislation imposing conditions of criminal liability stricter than those in force at the time the infringement was committed. By taking heed of the principle of legality as a fundamental right, guaranteed under both Union law and Italian constitutional law, the ECJ could avoid a clash between Union law primacy and the overriding principles of the Italian constitutional order.

A much more troubling national judgment is the more recent judgment of the German Federal Constitutional Court, following the ECJ judgment in Weiss, both judgments dealing with the legality of one of the programmes of the European Central Bank (ECB) for the purchase of government bonds on the secondary market.³² The Constitutional Court declared the ECJ judgment, which upholds the legality of the programme, ultra vires and not binding on it as, in its view, there had not been a proper assessment of the proportionality of the implications of the ECB programme for economic policy (which is not within the ECB’s core mandate, as compared to its monetary policy). In doing so, the German Court purported to impose a particular German approach to the principle of proportionality on the Union and the other 26 Member States.³³ The judgment thus goes far beyond a control of respect for the principle of conferral as a limit to the Union’s competence and constitutes an open challenge to the jurisdiction of the ECJ as well as the independence and status of the ECB as a Union institution. While it is too early to assess all the implications of the judgment for the Union legal order, it should be noted that the ECB, while not considering itself bound by the German judgment, has cooperated with the German Central Bank (which is a member of the European System of Central Banks) with regard to the available information relevant for a proportionality assessment. In view of this information, the German Central Bank and the German Government have determined that the Bank may continue to participate in the bond purchasing programme.³⁴ If subsequently the German Constitutional Court were to prohibit the German Central Bank from participating in the programme and the latter complied, the ECB could, under Article 35(6) of the Statute of the European System of Central Banks and the ECB, bring an infringement action against the German Central Bank before the ECJ.

An even more serious challenge to the Union legal order is posed by a judgment of the Polish Constitutional Court of 7 October 2021.³⁵ The judgment seems to call into question the very foundations of Polish membership in the EU as not only the Polish Constitution is declared to be supreme in relation to Union law but also Articles 1 and 19 TEU are found to be in contravention of the Constitution. While it is far too early to predict the final outcome of this constitutional crisis and a kind of attempt at withdrawal from the EU legal order, it may be noted that the dispute was triggered by Polish legislative and other measures appearing to compromise the independence and impartiality of the national judiciary and the ensuing decisions of the ECJ finding violations of Article 19(1) second sentence (right to effective judicial protection) and of the European Court of Human Rights finding violations of Article 6 of the European Convention on Human Rights.³⁶

These and other examples suggest that there is a grey area between national constitutional law and Union law, implying that, with regard to direct effect and/or fundamental rights in particular, national courts, notably constitutional courts, are not always ready to adhere to an unconditional principle of primacy. It should also be recalled that all Union legal acts, while they may be directly applicable, do not have a direct effect. Directives obtain this attribute only when the deadline for the transposition of the directive into national law has expired, and even then, the ECJ has, in principle, ruled out that directives may have a horizontal direct effect.³⁷ These caveats do not upend the fundamental conclusion to be drawn from the discussion so far: Union law is directly applicable at the national level and prevails, in principle, over national law, however framed. To what extent the caveats should be taken into account when making an overall assessment of the relationship between Union law and national law will be considered in the concluding section, after a discussion on the relevance of national law to Union law, to which I shall now turn.

3 The Relevance of National Law for Union Law

It is often assumed that the national legal order, while it may allow—or be compelled by the Union legal order to allow—the application of Union legal rules at the national level, does not form part of the Union legal order. Union institutions and bodies are supposed to interpret and apply Union law, while national law belongs to the realm of national authorities. This constellation is particularly conspicuous within the context of the preliminary ruling procedure, regulated in Article 267 TFEU, Article 23 of the Statute of the Court of Justice of the European Union³⁸ and Articles 93 to 118 of the Rules of Procedure of the Court of Justice.³⁹ The ECJ interprets Union law and the rules on the validity of Union secondary law, while the national court requesting a preliminary ruling interprets and applies national law.⁴⁰ This does not mean, however, that the state of national law would be irrelevant for the case pending before the ECJ. For the Union Court, it is necessary to understand the entire legal context of the case before the national court, and that is why Article 94 of the Rules of Procedure requires that the request for a preliminary ruling contain, inter alia, ‘the tenor of any national provisions applicable in the case and, where appropriate, the relevant national case-law’, as well as a statement of the reasons that prompted the national court to make a reference concerning the interpretation or validity of certain provisions of Union law and ‘the relationship between those provisions and the national legislation applicable to the main proceedings’.

The preliminary ruling context is far from the only situation where national law may become relevant for Union law purposes.⁴¹ First of all, it should be recalled that Union law has in many ways been inspired by national law and that in such instances, national law, or rather common national legal traditions, may serve as a secondary means of interpretation for Union law purposes. The most clear-cut example is the fact that the common constitutional traditions of the Member States are relevant for determining the fundamental rights which constitute general principles of Union law. The ECJ case law to this effect, starting with Internationale Handelsgesellschaft,⁴² is now codified in Article 6(3) TEU, which refers to the fundamental rights as general principles of Union law, not only as they are guaranteed by the European Convention on Human Rights (ECHR) but also ‘as they result from the constitutional traditions common to the Member States’. As to the EU Charter of Fundamental Rights, not only does its Preamble mention the constitutional traditions of the Member States as sources of inspiration, but also its Article 52(4) provides that fundamental rights resulting from the constitutional traditions common to the Member States ‘shall be interpreted in harmony with those traditions’.⁴³

Another example of an explicit reference to national legal traditions is to be found in Article 340(2) TEU, which states that the non-contractual liability of the Union shall be determined ‘in accordance with the general principles common to the laws of the Member States’. Article 340(3) refers in a similar way to the liability of the European Central Bank. As to contractual liability, Article 240(1) refers to the ‘law applicable to the contract in question’. This may entail the outright application of national law, as will be demonstrated below.

If there are no Union law rules regulating a certain area, and especially if there is no Union competence in that area, the situation is perceived to fall under an exclusive national competence.⁴⁴ Such situations do not completely escape the reach of Union law, however, as there may be features of the national law in question that are found to contravene Union law rules. National law, even if it is based on an exclusive national competence, must always be in conformity with Union law. If the issue comes before the ECJ through a request for a preliminary ruling, the Court may find that Union law ‘precludes’ the national law of a given content.⁴⁵ In order to arrive at this conclusion, the ECJ, while not being empowered to give an authoritative interpretation of national law, must necessarily have a certain understanding of the national rule at issue.⁴⁶

This is even more so in the context of infringement procedures initiated by the Commission (Article 258 TFEU) or a Member State (Article 259 TFEU) against a Member State for alleged failure to fulfil a Union law obligation. Such failure may stem from not only the behaviour of national authorities but also the contents of rules of national law.⁴⁷ While the ECJ in such cases does not have the competence to annul a national rule found to contravene Union law, a judgment of non-fulfilment may entail an obligation for the Member State in question to repeal or amend the national rule (and a non-fulfilment of that obligation again may lead to financial sanctions in accordance with Article 260 TFEU⁴⁸). In order to assess whether the national rule is in contravention of Union law, the ECJ must necessarily determine the meaning to be given to the national rule, also in situations when there is no or conflicting guidance provided by national case law. While such determination does not bind the national courts and the ECJ may be said to deal with national law as a question of fact rather than of law,⁴⁹ it remains the case that also national law is a normative rather than purely factual phenomenon. In any case, the distinction between questions of law and questions of fact is far from clear-cut.⁵⁰

While national law, in accordance with what has been said above, must always be in conformity with Union law, the latter also relies on national law to achieve its own purposes. According to Article 291(1) TFEU, Member States ‘shall adopt all measures of national law necessary to implement legally binding Union acts’. The main principle is thus that implementation takes place within the framework of the national legal order. Only where uniform conditions for implementation are needed that the Union legal act (normally a legislative act) shall, by virtue of Article 291(2), confer implementing powers on the Commission or, in some cases, the Council. The need to adopt national implementing acts is particularly obvious with respect to directives, but also regulations may be in need of national implementing measures.⁵¹ The obligation of Member States to adopt measures necessary to implement legally binding Union acts is supplemented by the obligation, provided for in Article 19(1) second sub-paragraph, to ‘provide remedies sufficient to ensure effective legal protection in the fields covered by Union law’.⁵² The basic Treaties, of course, contain numerous other obligations incumbent on the Member States, and some provisions refer to quite specific obligations to take measures, including measures to implement Union acts. To mention but one example, Article 325 TFEU refers to various obligations of the Member States and the Union to combat illegal activities affecting the financial interests of the Union, including, in Article 325(3), an obligation for the Member States to coordinate their actions and organise, together with the Commission, close and regular cooperation between the competent authorities.

Apart from such general references to the obligations of national authorities, Union law may contain more specific requirements with regard to the status and functioning of national bodies. An obvious and well-known example is the role of national courts as part of the EU legal system and the requirements stemming from Article 19(1) second sub-paragraph TEU referred to above, Article 47 of the EU Charter of Fundamental Rights (rights to an effective remedy and to a fair trial) as well as the above-mentioned Article 267 TFEU and the provisions of the Statute of the Court and its Rules of Procedure regulating the preliminary ruling procedure.⁵³ Sometimes Union law goes even further in instructing the Member States to designate certain national courts to perform specific Union tasks as required by Union law. An example is the requirement contained in Article 123 (1) of the Union Trade Mark Regulation,⁵⁴ entitled ‘EU trade mark courts’, which provides that the Member States ‘shall designate in their territories as limited a number as possible of national courts and tribunals of first and second instance, which shall perform the functions assigned to them by this Regulation’. These functions include infringement actions and counterclaims for revocation or a declaration of invalidity of the EU trademark.⁵⁵

There are also instances—in fact, an increasing number of instances—where national administrative bodies are harnessed for specific Union law purposes. Union law, in other words, requires the existence of certain national bodies, often referred to as ‘national regulatory authorities’ (NRAs), and contains some rules on their status and tasks. Examples are to be found in the areas of energy, telecom, airport slots for flights and data protection.⁵⁶ There is an abundance of ECJ case law, notably on the question of whether such NRAs are, under national law, sufficiently independent from other parts of the administration, as required by Union law.⁵⁷ Union law in such cases may be said to intervene in the national administrative apparatus and national administrative law of Member States, while at the same time national law and national administrative bodies become vehicles for the application and implementation of specific purposes of Union law. While it is still possible to maintain the idea that in such instances Union bodies, such as the Commission or the ECJ, do not directly apply national law (although they may assess whether national law is in conformity with Union law), the NRAs may be said to form part of an EU administrative system in the broad sense of the term, in a similar way as the national courts, in accordance with what has been said above, form part of an EU judicial system.

There are some—albeit rare—instances when a Union body may be deemed to apply national law as a question of law rather than of fact. One example is again offered by the Union trademark legislation. Article 8 of Regulation 2017/1001 lists a number of relative grounds for the refusal to register a trademark, in other words grounds that are only triggered upon opposition by the proprietor of an earlier trademark, including, as the case may be, a non-registered trademark or another sign used in the course of trade of more than mere local significance. The rights of proprietors of such non-registered trademarks or other signs are regulated in Article 8(4), which provides that the trademark applied for shall not be registered to the extent that, ‘pursuant to Union legislation or the law of the Member State governing that sign’, rights to the sign were acquired earlier and the sign confers on the proprietor the right to prohibit the use of a subsequent trademark. Article 60(1) extends the relative grounds for refusal, including the ground mentioned in Article 8(4), to relative grounds for invalidity. A similar reference to not only Union legislation but also national law is to be found in Articles 8(6) and 60(1)(d) concerning certain designations of origin and geographical indications.

ECJ case law is based on the idea that in such situations, national law may become applicable, and hence its contents have to be determined.⁵⁸ The Court, in referring to the ‘application of national law’, has observed, inter alia, that lacunae in the documents submitted as evidence of the applicable national law cannot prejudice an effective judicial review and that, to that end, the Court ‘must therefore be able to confirm, beyond the documents submitted, the content, the conditions of application and the scope of the rules of law relied upon by applicant for a declaration of invalidity’.⁵⁹ True, the Court has referred to the relevance of national case law and the literature and seems to consider that on questions of interpretation, national case law, if it is unambiguous, should be relied upon in particular. On the other hand, the Court has stated that it does not follow from an earlier judgment⁶⁰ that a relevant rule of national law, ‘made applicable’ by a reference in the Trade Mark Regulation, ‘should be treated as a purely factual matter, the existence of which [the EU Intellectual Property Office] and the Court merely establish on the basis of the evidence before them’.⁶¹ The content and scope of the relevant rule of national law must, if necessary, be determined ex officio and judicial review be conducted in accordance with the principle of effective judicial protection.

Another instance where national law has to be applied at the Union level is to be found in the Union legislation relating to the banking union. According to Article 4(3) of a Regulation concerning policies relating to the prudential supervision of credit institutions,⁶² the European Central Bank (ECB) shall apply, apart from the relevant Union legislation, and where that legislation consists of directives, ‘the national legislation transposing these Directives’. Where, again, the relevant Union law takes the form of regulations and where those regulations ‘explicitly grant options for Member States, the ECB shall apply also the national legislation exercising those options’. Article 4(3) has been considered quite exceptional and also problematic.⁶³ The proposal of the Commission was based on the idea of using national authorities as intermediaries in the application of national law, coupled with the objective of a gradual harmonisation of national law with a view to enabling the ECB to apply a more comprehensive and precise Union legislation. Since especially the Member States that are not part of the euro area did not like the prospect of further harmonisation, the end result was to give to the ECB the task to also apply national law, even if divergent.⁶⁴

Yet another context where national law may be directly applied by Union bodies is in the settling of disputes concerning contracts entered into by the Union. According to Article 272 TFEU, the Court of Justice of the European Union ‘shall have jurisdiction to give judgment pursuant to any arbitration clause contained in a contract concluded by or on behalf of the Union, whether that contract be governed by public or private law’. And Article 340(1) TFEU provides that ‘[t]he contractual liability of the Union shall be governed by the law applicable to the contract in question’. The ECJ has observed that the latter provision ‘refers, as regards the law applicable to the contract, to the Member States’ own laws and not to the general principles common to the legal systems of the Member States’.⁶⁵ With respect to Article 272 TFEU, as the parties may have submitted their contractual relationship to a national law (which is often Belgian law), and if there is disagreement as to the terms of the contract or the applicable law, the Union courts (at first instance, the General Court, whose decisions may be appealed before the ECJ) may have to apply, and if need be interpret, the applicable national law.⁶⁶

While national law may thus in different ways be of considerable relevance to Union law and may even in some instances be applied directly by Union bodies, it should hitherto be presumed that Union courts may not directly annul national legal acts. It is up to the national legislature and other authorities to draw the necessary conclusion as to whether a national act has been found to be in contravention of Union law. There is at least one exception to this rule, however. According to Article 14.2. of the Statute of the European System of Central Banks and of the ECB, the governor of a national central bank and the ECB may refer a national decision to relieve the governor from office to the ECJ. In a recent judgment concerning the decision to temporarily prohibit the Governor of the Latvian Central Bank from performing his duties, the ECJ held that such an action constitutes an action for annulment, comparable to actions under Article 263 TFEU.⁶⁷ According to the ECJ, the European System of Central Banks ‘represents a novel legal construction in EU law which brings together national institutions, namely the national central banks, and [a Union] institutions, namely the ECB, and causes them to cooperate closely with each other, and within which a different structure and a less marked distinction between the EU legal order and national legal orders prevails’.⁶⁸

4 A Common Legal System

As the original Community Treaties of the 1950s were not constructed and drafted as comprehensive constitutional instruments but rather formed a patchwork of some general principles of constitutional relevance and a host of fairly detailed provisions of a more technical nature, the task of making sense of it all, including clarifying the relationship between Community law and national law, fell upon the ECJ.⁶⁹ After Van Gend & Loos (1963) and Costa v ENEL (1964),⁷⁰ the idea has gained ground that Community law can be applied and invoked directly in the legal orders of the Member States and, when being so applied, enjoys primacy over ‘purely’ national rules. These principles are not dependent on national constitutional principles but follow directly from Union law, which is in this sense to be seen as forming part of national law. It is true that some constitutional or other national courts have formulated certain reserves in this respect, usually linked to the idea that there is an ‘ultimate’ national control mechanism that can verify whether the Union has acted within the confines of its competence, in accordance with the principle of conferral. These reserves are rarely brought to the fore, however, and do not upend the fact that under normal circumstances the direct applicability, direct effect and primacy of Union law are accepted also at the national level. It is too early to assess whether the recent judgments of the German Federal Constitutional Court in Weiss and by the Polish Constitutional Tribunal assessing the conformity of the TEU with the Polish Constitution will present a more serious challenge to the principle of primacy of Union law and to the Union legal order in general.⁷¹

Already for the above reasons, it is obvious that there is a close link between Union law and national law. This close link becomes even more obvious when the application of Union law at the national level is supplemented by shifting the focus to the relevance of national law in Union law contexts. As hopefully demonstrated by the discussion in Sect. 3 above, the Union legal order draws upon, harnesses, and instrumentalises and its institutions sometimes even apply national law, which is an indispensable component of the overall system. As the direct applicability of national law by Union institutions is still quite exceptional, it would go too far to equate the status of national law in the Union legal order with that of Union law in the national legal order. And if the notion of legal order is reserved for systems that are bestowed with such a norm hierarchy that norms of a lower hierarchical order may be invalidated because of incompatibility with norms of a higher order, then the Union and national legal systems may still be considered two distinct legal orders. As Union institutions are, as a general rule, empowered not to annul national legal acts but only to declare their incompatibility with Union rules, I prefer to speak of the primacy rather than supremacy of Union law over national law.⁷²

That said, it is undeniable that there is a close interrelationship between Union law and national law. A well-known commentator has argued that they form a common legal space.⁷³ I would go somewhat further and say that one can speak of a common legal system made up of historically distinct legal orders.⁷⁴ A legal order is an order if the norms constitute a unity, have the same basis of validity, and are characterised by an internal norm hierarchy.⁷⁵ The notion of a legal system is here used as a somewhat broader doctrinal tool, referring to a more open system not where the validity of a norm of one legal order necessarily depends on a norm of another order belonging to the same system but where the norms of both order are nevertheless closely interrelated.

As was noted in Sect. 1, the ECJ has referred to ‘[t]he autonomy enjoyed by EU law in relation to the laws of the Member States and in relation to international law’.⁷⁶ While the notion of autonomy is entirely appropriate when it comes to the relationship between Union law and public international law,⁷⁷ it is much less obvious that it is the best way of characterising the relationship between Union law and national law. Nor is it, in my view, appropriate to speak of the ‘procedural autonomy’ of Member States as, in view of a well-established general principle of Union law, now codified in Article 19(1) second sub-paragraph TEU, there is an obligation of the Member States to provide remedies with a view to ensuring effective judicial protection rather than any autonomous right of the Member States to maintain their own procedural system regardless of the existence of applicable Union law provisions.⁷⁸

Does the fact that there are at least 27 national legal orders in the EU upend the idea of a common legal system? I do not think so. Let us compare the situation with that of federal states. They consist of sub-federal states that all have their own constitutional system and may under federal constitutional law even enjoy a default competence (competence for all matters not reserved for the federal level). Yet federal and state laws are considered to be a part of a common legal system and, depending on how these concepts are understood, even a part of the same legal order. In the same way as with regard to the sub-federal units of a federal state, the national law of an EU Member State may differ from that of another Member State. These differences are on the other hand mitigated and circumscribed by EU law (through harmonisation and other measures). Moreover, even in situations where differences between two national legal orders persist, this does not prevent national law from being directly relevant for Union law purposes and sometimes even from being applied by Union bodies. Especially, the latter function may, of course, lead to different outcomes in different Member States. ‘Unity in diversity’ seems an appropriate slogan to describe this state of affairs as well.