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date: 07 March 2021

The Legal History of the European Union: Building a European Constitutionfree

  • Morten RasmussenMorten RasmussenThe SAXO Institute, University of Copenhagen


Attempts to analyze and understand how European law developed from a set of international treaties in the 1950s to a constitutional, proto-federal legal order, accompanied by a constitutional legal discourse today, has been a key concern in European studies in the last three decades. Legal scholars, political scientists, and sociologists have explored this from their specific disciplinary viewpoints and have produced a rich literature of sophisticated theoretical as well as empirical studies. Since the mid-2000s, historians have also finally—after years of negligence—taken an interest in European law and produced a new body of archive-based studies of the history of European law from 1950 to 1993. Based on primary sources drawn from private, national, and European archives, historians have contributed with much new empirical information and managed to uncover the social, political, and legal forces that have shaped European law in a qualitatively new way. The central argument is that the constitutionalization of European law was part of the broader battle over the political and institutional soul of the European construction. Even though the ECJ successfully constructed a European legal order that resembled and worked as a proto-federal constitution, the project ultimately suffered a defeat in not being able to codify this achievement in the Maastricht Treaty as part of a broader step toward a federal Europe.


One of the most unique features of the European Union (EU) is the legal order underpinning it. Despite its origins in international treaties, the EU is today based on a pro-federal, constitutionalized legal order, and European politics have been partly judicialized. It is therefore not surprising that scholarly interest in European law has become one of the most important fields in European studies, attracting not only legal scholarship but also political scientists, sociologists, and most recently historians. Studies on European legal integration have consequently become a melting pot for different disciplines, approaches, and methodologies. Until recently, historians had almost completely ignored the legal dimension of the integration process (consult, for example, the publication series of The European Union Liaison Committee of Historians). The first generation of integration historians, perhaps because of the lack of access to the archive of European Court of Justice (ECJ), exhibited a certain reluctance to address a phenomenon as technical and specialized as law. In the last decade this state of affairs has changed, however. A group of younger historians have begun to explore the history of European law and, through the systematic use of multiple private, state, and European archives, have attempted to offset the lack of access to the ECJ archive until 2017. The result is a rich body of archive-based studies that not only has produced important new insights but today constitutes a genuinely new interpretation of the history of European law. This article takes stock of this new historiography in four sections. First, the “State of the Art of Legal and Social Science Scholarship on European Law” is reviewed. Second, in “What Kind of Legal History?,” a closer look is taken of what kind of legal history has been produced about European law. Third, in “Toward a New History of European Law,” the most important contributions and the new historical interpretation of EU legal history are explored. Finally, in the “Conclusion,” the results of the new historiography are discussed in comparison with existing interpretations of law and politics studies.

State of the Art of Legal and Social Science Scholarship on European Law

The first legal scholarship on European law was published in the 1950s, in parallel to the development of the European construction with the European Coal and Steel Community (ECSC) (1952) and the European Communities (EC) (1958), and was often quite explicit about the politics at stake in the legal dimension of the integration process. It was, however, only when the ECJ pronounced that European law constituted a “new legal order” in its seminal judgments of Van Gend en Loos (1963) and Costa v. ENEL (1964) that a clear disciplinary identity of European law, separate from traditional international law or comparative law, emerged. In the 1960s and 1970s, legal scholarship became more “formalist,” focusing on and legitimating the case law of the ECJ and avoiding too-explicit discussions about the political implication of European law (Boerger & Rasmussen, 2014; Byberg, 2017a). A scientific maturing of the field took place during the 1980s, with a turn toward “law in context” spearheaded by the Department of Law at the new European University Institute (EUI) in Florence. Partly inspired by the work of the American scholar Eric Stein, who first developed the notion that the ECJ had constitutionalized the Treaties of Rome and through its case law built a proto-federal European legal order (Stein, 1981), EUI professor Mauro Cappelletti and his young protégé, Joseph H. H. Weiler, launched the “Integration through Law” project, which compared European legal integration vis-à-vis the American model (Byberg, 2017b). Another sign of a maturing field was the provocative and influential work by Danish legal scholar Hjalte Rasmussen, who, in his 1986 magnus opus “On Law and Politics in the European Court of Justice,” argued that the European Court of Justice had become too activist and also claimed that the ideological roots of the Court’s case law were to be found in European federalism (Rasmussen, 1986). Eventually, it would be Weiler’s work in particular that would shape what was becoming the central orthodoxy in European legal scholarship. In the early 1990s, he argued that European law, through constitutionalization, had developed into a supreme legal order, with directly effective legal norms supported by strong enforcement mechanisms. Whereas national governments had accepted this because the national veto right, which resulted from the 1966 Luxembourg compromise, protected their interests, national courts had even helped drive constitutionalization by cooperating with the ECJ (Weiler, 1991, 1994).

At the end of the Cold War, European integration was at its apogee, and as a result attracted the attention of the brightest young political scientists of the top American universities. Many of these young scholars found the unique development of European law particularly interesting because it challenged standard assumptions of international politics theory. Writing within the paradigm of constitutionalization, scholars such as Geoffrey Garret (1995), Anne-Marie Burley and Walter Mattli (1993), Alec Stone Sweet (2000, 2004), Stone Sweet and Thomas L. Brunell (1998, 2004, 2012), Karen Alter (2001), and Lisa Conant (2002) explored how the process had worked and developed alternative theories in order to explain it. These theories mirrored classical debates in political science, one being an intergovernmental explanation that legal integration was driven by the national interests of the largest member states (Garret, 1995) over neofunctionalist accounts of self-sustaining legal integration caused by a virtuous circle constituted by litigation, case law facilitating the liberalization of trade and more litigation (Stone Sweet, 2000, 2004; Stone Sweet & Brunell, 1998); and another comprising a historical institutionalist analysis of how institutional dynamics between national courts spurred cooperation with the ECJ despite significant national resistance to constitutionalization (Alter, 2001). These foundational studies have been followed more recently by new attempts by political science to understand legal integration. Several scholars have emphasized how member state reception of constitutionalization was much more critical and piecemeal (e.g., Conant, 2002; Martinsen, 2015; Wind & Martinsen, 2010; Wind, Martinsen, & Rotger, 2009). Others have argued that because of the constitutionalization of European law and the rise of the ECJ as a central institution in the EU, European politics have become thoroughly judicialized to the extent that ECJ case law ultimately trumps Council decision-making (Davies, 2016; Kelemen, 2011; Stone Sweet & Brunell, 2012). Recent sociological scholarship has also focused on processes of judicialization and, through the lenses of Bourdieu sociology, argued that self-empowering jurists since the 1960s have managed to turn European law and legal expertise into the very backbone of the European Union (Bailleux, 2014; Vauchez, 2015; Vauchez & De Witte, 2013).

Whereas social science research has generally been conducted within the paradigm of constitutionalization, legal scholarship has recently begun to question it. Already in the wake of the Maastricht Treaty (1991) and the famous Maastricht judgment of the German Constitutional Court in 1993, which undermined the constitutional nature of the EU, legal scholars began to rephrase the constitutional narrative to reflect the new reality of a stand-off between the constitutional claim for the autonomy of European law by the ECJ and the opposing claim of national supreme courts that the competences of the EU were only delegated by the member states. Today, constitutional pluralism has become part of a mainstream of legal studies (Avbejl & Komárek, 2012) that still emphasize the constitutional nature of European law (Schütze, 2016). Vocal critics have emerged recently, such as American legal scholar Peter Lindseth, who, through historical analysis, has highlighted the administrative roots of European law; or the leading German professor in constitutional law (Lindseth, 2010), Dieter Grimm, who claims that European law is not yet fully constitutional measured against the standards of national constitutional history (Grimm, 2015).

What Kind of Legal History?

In this diverse field of interdisciplinary research, historians began to publish archive-based studies of EU legal history from 2008 onward (Journal of European Integration History, 2008, Volume 14, Number 2). The first conference on the topic was held at University of Copenhagen in 2007. It was followed by a collective research project at that same university from 2012 to 2016 funded by the Independent Research Fund Denmark, which came to serve as a hub for the larger network of historians working in the field. Since 2017, the Max Planck Institute for European Legal History has hosted the activities of the network. Almost all the participating historians came from the field of European integration history and had no prior legal training. Their background was reflected in the approach and methodology with which they approached the legal history of the EU. Where traditional legal historians begin their study with the written legal texts—for example constitutions, international treaties or case law—or focus on the intellectual history of the most important legal personalities, historians of EU legal history have approached the topic as if they were simply writing a part of the broader political history of the EU. Using the methodology of political history, the focus has been on providing the best possible empirical foundation for the analysis by exploring all relevant archival resources systematically, and not merely selectively to illustrate certain theoretical points. In addition, there has been an emphasis of analyzing the concrete social practice of European law and contextualize it within the broader history of European integration. As a result certain interests of traditional legal history has been neglected, including the doctrinal and intellectual history of European law. However, what has instead been produced is a rich, well-contextualized history, focusing on the social practice of European law and laying bare in full empirical detail the multiple links between European law and the institutional, political, and ideological history of European integration. The main focus of the first generation of EU legal historians has perhaps quite naturally been what they have called the battle over the constitutional practice of European law (Davies & Rasmussen, 2012), thus following in the footsteps of law and social scientists. The results of historical research, however, seriously question whether mainstream legal and social science have got it right when explaining the development of European law until 1993 as a progressive history of constitutionalization. In a situation in which legal history dealing with international and European history during the 20th century is increasingly turning away from intellectual history (Koskenniemi, 2001) toward the study of practice based on the systematic use of archival sources (e.g., Duranti, 2017; Genin, 2018; Payk, 2018), the new field of EU legal history has become part of the new vanguard of legal history.

Toward a New History of European Law

With the focus on how a constitutional practice developed in European law, historians have not strayed far from the original agenda of law and politics studies. However, the archive-based and contextual approach chosen means that this classical object of study is explored empirically more in depth, with primary sources allowing us to go behind the closed doors of jurists and decisions-makers in order to better understand the nature and complexity of their motives. Likewise, the informal politics and networks that shaped the history of European law can finally be accessed in full empirical detail. In the last decade, historians have primarily explored five core dimensions of the history of the constitutional practice. First, a number of studies have analyzed how the institutional and legal design of the European construction was developed in the Treaty of Paris (1951) and the Treaties of Rome (1957) (Boerger, 2012; Delfs, 2015; Wilson, 2008; Wilson & Schroeder, 2005). Second, historians have explored how the European supranational institutions together developed a constitutional practice of European law, focusing in particular on the roles of the European Court of Justice (Fritz, 2018; Rasmussen, 2010b) and the European Commission (Bailleux, 2014; Boerger & Rasmussen, 2017; Rasmussen, 2012, 2014b). Third, transnational links between the European institutions, transnationally organized legal elites and national legal elites have been explored historically by both social scientists and historians (Alter, 2001; Bernier, 2012; Byberg, 2017c; Leucht, 2010; Rasmussen, 2014a; Vauchez, 2010). EU law academia played an important role in these networks and also more generally in legitimating the constitutional practice launched by the ECJ and the Commission (Boerger, 2014; Boerger & Rasmussen, 2014; Byberg, 2017a, 2017b; 2017c; Vauchez, 2015). Fourth, the reception of European law by several member states has been explored. However, given the tremendous task of doing a well-contextualized and archive-based study of national reception over several decades means that not all member states have yet been covered. Most well developed is the work on Germany (Davies, 2008, 2012a, 2012b, 2015; Mangold, 2011, France (Bailleux, 2014; Bernier 2012, 2016, 2018), the Netherlands (Van Leeuwen, 2012, 2018) and Denmark (Pedersen, 2016). Finally, less work has been devoted to the concrete ways ECJ case law influenced the integration process. Most importantly, work has been devoted to the history of competition law and the common market (Leucht, 2010, 2018; Patel & Schweitzer, 2013; Warlouzet & Witschke, 2012). Other pioneering efforts have been devoted to the history of the case law on direct effect (Rasmussen, 2014b, 2017). With regard to developing a new historical interpretation of the development of European law, the first step taken was published in a special issue of Contemporary European History in 2012 (Davies & Rasmussen, 2012), focusing on the 1950s and 1960s. This was later followed up by several articles also addressing the 1970s (Davies & Rasmussen, 2014; Rasmussen, 2013, 2014b) and most recently the entire period from 1950 to the early 1990s (Rasmussen, 2018). As can be seen, there are important fields of inquiry completely open to new researchers, including the intellectual history of European law, the history of ECJ case law in key policy fields such as agriculture or social policy, the administrative history of the ECJ (the administrative archive of the court is being declassified at the moment), and the procedural history of the ECJ.

What are the results of this new historiography? To what extent has it recast our understanding of how European law developed from 1950 to the early 1990s? To answer these questions, a chronological look is taken at the history of European law from 1950 to 1993, in order to present not only the most important new insights but also an overall narrative and interpretation of the nature and result of the battle over the constitutional practice that developed in European law in this period.

From the outset of the history of European integration, the European construction was an open-ended project both in terms of its political finalité, its institutional and legal shape, and its fields of cooperation, shaped as it was by both traditional state practice and European federalism that reached its apogee in the 1950s. The Treaty of Paris and the Treaties of Rome were ambiguous in their definition of the nature of the European institutions and the legal shape of the European construction. Although the autonomy of the supranational institutions decreased from the ECSC, as the Council of Ministers took center stage in the EC, the Treaties of Rome could still be meaningfully interpreted both as international law, the execution of which was based on the political will of the member states, and as the beginning of a federalizing process toward an “ever closer union” (Boerger, 2014). What would eventually decide the direction of European integration was a political battle between the political and institutional forces favoring federalization and the resistance to such a development in national political and administrative elites (Ludlow, 2006).

Key protagonists in this battle were the supranational executive, the High Authority of the ECSC (HA) and the Commission of the EC. Led by important figures such as Jean Monnet (1952–1955) and Walter Hallstein (1958–1966), the supranational executive became a hotbed for federalist ambitions. Although Hallstein, for example, did not have any illusions about the longevity of the process embarked on, he still wanted to put the new EC on track toward gradual federalization. The legal dimension of the integration process was considered crucial by Hallstein, who had a background as a professor of international, private, and civil law. The legal service of the HA and the Commission had early on conceived of European law as potentially constitutional and a key tool for the consolidation of the competences of the supranational executive. The hope was that the ECJ would take a constitutional responsibility and establish itself as a European supreme court. The promotion of a constitutional understanding of European law was thus very much part and parcel of the Hallstein Commission’s federal project from 1958 to 1967, which ultimately failed with the famous Empty Chair crisis in 1965, where France boycotted the Council, with the result that an informal national veto right was introduced in 1966, and Hallstein ultimately had to resign (Boerger & Rasmussen, 2017; Rasmussen, 2014b). At the very roots of European constitutionalism was thus an intimate connection to both federal ideology but also the consolidation of the role of the supranational executive in the European construction.

In the 1950s, it did not really look like the constitutional interpretation of European law promoted by the HA and the Commission would achieve a breakthrough. National governments and legal elites did not take seriously what was regarded as a politicized theory of law, and the ECJ was relatively timid in terms of its case law and did not follow the lead of the legal service. Despite this resistance from the member states, the breakthrough of the constitutional interpretation of European law already came in the first half of the 1960s. Several factors came together to make it happen. First, the composition of the judges on the bench shifted in 1962 with the nomination of, respectively, French judge Robert Lecourt and Italian judge Alberto Trabucchi, who both would be instrumental in pursuing a constitutional interpretation (Rasmussen, 2010a, 2010b). Second, the legal service of the Commission led by Michel Gaudet developed a constitutional reading of the Treaties of Rome that focused on the necessity of providing the new common market with a strong legal underpinning instead of emphasizing explicitly federalist ambitions. This gave a broader, politically less explicit, rationale for separating European law from international law (Rasmussen, 2012, 2014b). Third, the Netherlands brought a key innovation of the EEC Treaty into life, namely the preliminary reference mechanism that gave the ECJ the jurisdiction to interpret European law on the basis of questions sent by national courts. The unique constitutional reforms of 1953 and 1956 in the Netherlands that granted self-executing international law primacy over national law propelled Dutch courts to ask the ECJ whether any of the legal norms of the EEC treaty had that same quality (Van Leeuwen, 2012). The Van Gend en Loos case was the first dealing with this question to reach the docket of the ECJ. The case finally offered Gaudet and the legal service the chance to submit a complete interpretation of the nature of European law, with the backing of Hallstein and the Commission collegium, before the court. The key objective of Gaudet was to carve out a genuine droit communautaire, uniformly interpreted across member states and efficiently enforced, of the disparate and incoherent treaties: a European legal order that would provide a solid legal underpinning of the common market and the political Europe of the future. The main challenges concerned the different constitutional clauses of the member states with regard to their reception of international law into the national legal orders, which meant that European law would not be interpreted uniformly by national courts. In addition, the infringement proceeding outlined in article 169 was also too cumbersome and political in nature to efficiently solve the problems that could be expected with member state enforcement of European law. Gaudet’s bright idea was to sidestep this problem by letting the ECJ define the status of European legal norms inside the national legal orders. By granting primary legal norms direct effect and primacy, that is, immediate effect in the member states and primacy vis-à-vis national legislation both prior and antecedent, decided on a case-by-case basis of the ECJ, national judiciaries would be in no doubt about the exact effects of European legal norms. In addition, such a system would give private litigants the opportunity to police the implementation of European law in the member states through national courts. In the two judgments of Van Gend en Loos (1963) and Costa v. ENEL (1964), the ECJ followed the advice of the legal service and fundamentally recast the nature of European law into what the Court modestly in 1964 called “a new legal order.” It was in fact launching what resembled a proto-federal hierarchical legal order based on the twin pillars of direct effect and primacy and with a transformed preliminary reference mechanism that now allowed private litigants to police the enforcement of European law in the member states (Rasmussen, 2014b; Rasmussen, 2015). To Hallstein the two judgments represented a crucial breakthrough of his federalist project, as he explained in the European Parliament in 1965. The European Parliament warmly supported the breakthrough in European law and thus joined the ECJ and the Commission in a supranational alliance favoring the constitutional interpretation of European law (Vauchez, 2015). However, with the defeat of the Hallstein Commission in the Empty Chair crisis and the rise of inter-governmentalism in the EC after 1966, the constitutional breakthrough in European law looked extremely fragile.

How was it possible for the constitutional interpretation of European law to survive the defeat of the Hallstein Commission and to develop by the early 1990s into a veritable constitutional practice constituted by a proto-federal and constitutional legal order as well as a legitimating constitutional discourse? The answer to this crucial question consists of several elements and is explored in the remainder of this article. A crucial precondition was the continuation of the supranational alliance favoring the constitutional interpretation of European law. The Commission continued to use the constitutional interpretation of European law both before the ECJ and in its various work on treaty reform in the 1970s and 1980s. Likewise, the European Parliament, dominated as it was by pro-European politicians, continued through the work of the legal committee to write supportive reports favoring new doctrinal developments in European law and urging the member states to cooperate in the field of legal integration (Rasmussen, 2018). Finally, the ECJ continued and even intensified its efforts to build a constitutional legal order after 1967. Historical research, exploring for the first time the nomination of judges from the 1950s to the 1970s on basis of primary sources, has demonstrated that the nomination process was determined by domestic party and administrative politics as well as personal connections. The nominated judges were thus a result of internal battles in the governing coalitions of the member states, and therefore typically reflected the pro-European outlook that such coalitions generally held. The main exception here was France, but even here the presidents and governments of the 1970s and the 1980s never really intended to endanger French EC membership, and for various reasons ended up nominating pro-European judges. The result was that a solid pro-European majority dominated the ECJ from mid-1962 onward and supported the constitutional case law that had been initiated in 1963–1964 (Bernier, 2018; Fritz, 2018).

With the supranational alliance intact, the ECJ was able to exploit the redesign of the preliminary reference mechanism that allowed private litigants to use European law to circumvent and question national law. This mechanism would be instrumental as a key means to produce the case law the ECJ needed to build the constitutional European legal order. However, social science research has generally overemphasized the importance of the gradual rise in the number of preliminary references from 1961 to the 1980s and sought to explain it structurally. Either the rise reflected the virtuous circle whereby private firms used the mechanism in order to produce ECJ case law that would liberalize the national economies or the increased cooperation of lower national courts (Alter, 2001; Stone Sweet & Brunel, 1998). Within the social sciences the work by Stone Sweet and Brunel has been criticized for faulty econometric assumptions (Wind, Martinsen, & Rotger, 2009). What has perhaps generally been overlooked is that the actual number of cases from 1961 to the mid-1980s was relatively low and hardly can be said to reflect a significant societal demand for legal integration or any widespread cooperation of national courts (Davies & Rasmussen, 2014). Likewise, much has been said about the importance of the preliminary reference mechanism to the enforcement of European law. However, despite the original hope of Gaudet that it would make a real difference, it was apparently not enough to solve the serious lack of enforcement by the member states. By 1977, the legal service of the Commission felt the need to act and decided to ramp up the infringement procedure and systematically go after member states that did not implement European law properly (Vauchez, 2015). We should therefore reassess the importance and role of the preliminary reference mechanism. Qualitative and archive-based explorations of the use of the mechanism show that many cases, and often the most important, were driven by pro-European lawyers who, beyond professional interests, had a clear agenda of furthering the development of the European order. In Italy, for example, 60 out of the first 89 preliminary references were produced by the same four pro-European lawyers, two of whom came from the legal service of the Commission and the ECJ, respectively (Pavone 2017). As demonstrated also by recent social science research, albeit on a later time period (Conant, 2002; Martinsen, 2015; Wind & Martinsen, 2010), national courts were generally much more passive and conservative than theorized by the social science literature and lawyers would often even formulate the preliminary reference itself (Bernier, 2018; Pavone, 2017). The key question for future research therefore seems to be to what extent pro-European lawyers were able to shape ECJ case law by promoting areas of European law that were particularly “ready” for doctrinal advance. All in all, the preliminary reference mechanism allowed the ECJ to receive enough good cases to construct a relatively impressive constitutional legal order in three decades—a legal order that, to a significant extent, was ready to underpin the single market launched by the Single European Act in 1986, included references to fundamental rights, had fully developed its claim for constitutional autonomy as well as the constitutional position of the European Parliament vis-à-vis the other institutions, and had expanded the doctrine of direct effect to large parts of the primary law of the original treaties as well as the legislative category of directives (Dehousse, 1998).

With the gradual development of a proto-federal and constitutional European legal order in the 1970s and 1980s, the emergence of a legitimating constitutional discourse had in fact been lacking behind. This was in a way not accidental. When the ECJ had launched the constitutional interpretation of European law in 1963–1964 it had deliberately avoided any constitutional rhetoric and instead used the terminology that European law constituted a “new legal order.” The political defeat of the Hallstein Commission and the rise of inter-governmentalism in the EC did not make it opportune to make explicit the deeper nature of how the ECJ now interpreted European law. This was reflected in the new field of European law academia that broke through at the universities of the member states in the 1960s and 1970s. Here the approach to European law was formalist and technical, and although European law academics largely endorsed and legitimated the case law of the ECJ, whereas national legal elites in general were much more critical, they seldom explicitly discussed what was the nature of this new type of law. When the critique by national legal academia grew strongly in the 1970s, as the ECJ advanced its case law, for example, on fundamental rights, the key purpose of European legal discourse was rather rearguard actions to dispel accusations that the ECJ acted as a government de juge (Boerger & Rasmussen, 2014; Byberg, 2017b). Unsurprisingly perhaps, this timid academic approach to European law changed in the last half of the 1980s reflecting the Single European Act in 1986 and the new intensified dynamics of European integration leading to the Maastricht Treaty and the formation of the EU. The change came before the new breakthrough for European integration, however. It began with a famous article by American legal scholar Eric Stein in 1981, based on a “law in context” approach that argued that the ECJ had “constitutionalized” European law and carved out a constitutional and proto-federal legal order from the Treaties of Rome (Boerger, 2014). This notion was adopted by the large research project of “Integration though law” conducted by Mauro Cappelletti and Joseph Weiler at the EUI in the first half of the 1980s and formed the read thread in the comprehensive book series, comparing the American and European experience in legal integration, that resulted from the project. By the early 1990s the notion promoted, in particular in the writings of Weiler, that the EC was now based on a constitutional legal order became the mainstream view both within European law academia and within the broader European studies (Byberg, 2017b). This breakthrough for a constitutional discourse in European law was promoted also by the ECJ in the Les vertes judgment of 1986 (Boerger & Davies, 2017) and in the writing of prominent judges (Mancini, 1989).

Although the ideological choices underlying the case law of the ECJ were finally openly admitted by the late 1980s and early 1990s, the Commission and European Parliament had systematically used the constitutional interpretation of European law in its various treaty reform plans during the 1970s and 1980s. This was, for example, the case when the European Parliament in 1984 launched the Draft Treaty establishing a European Union initiated by Altiero Spinelli. The latter worked closely with the EUI Department of Law to define a set of fundamental rights (drafted by Joseph Weiler, Jean-Paul Jacqué, and Meinhard Hilf). (Vauchez, 2015) The draft treaty was never accepted by the national governments. Subsequently, the Commission of Jacques Delors also took the constitutional legal order developed by the ECJ as a starting point for their reform proposals for a single constitutional order, with increased autonomy for the supranational institutions in the negotiations on the Maastricht Treaty. Again, national governments rejected the proposal to finally codify the constitutional legal order developed by the ECJ or to move further in the direction of a European federation with increased autonomy and power to the supranational institutions. Instead, they opted for a treaty that introduced two additional pillars based on intergovernmental cooperation that splintered the constitutional unity of the European project, and they did not agree to codify the constitutional case law of the ECJ (Loth, 2013; Ludlow, 2013).

By the early 1990s, national governments could thus not agree to codify the constitutional legal order built by the ECJ. The new historical research has in many respects improved our understanding of how national governments reacted both at the European and national levels to the constitutional practice emerging in European law. Already in the 1960s, national governments had split at the European level in their view on the constitutional breakthrough in the interpretation of European law, and this split continued to paralyze the Council with regard to taking a stand on general questions related to European law. The positions crystallized during the negotiations of the 1968 Brussels Convention (Fritz, 2015), but remained in place and blocked action during the 1970s at several occasions when the advances of the ECJ’s case law were discussed. On the one hand, France—often supported by Britain and sometimes also by Germany and Belgium—criticized the ECJ and contemplated possible court reform (Bernier, 2018; Rasmussen, 2017). On the other hand, the Netherlands, Luxembourg, Italy, and even euro-skeptical Denmark supported the ECJ as a means to protect the smaller member states (Pedersen, 2016). Although this split in the Council may have blocked any action against the ECJ from unsatisfied governments, it also made it impossible for the member states to agree on the full codification of the constitutional doctrines developed by the ECJ.

All in all, it is quite clear from the new documentation drawn from national archives that there was never much urgency to the calls for court reform, compared to other more important challenges in the integration process such as the prices of agricultural products, the development of the common market and the financing of the community. A key reason for this was the broad resistance of national administrations and courts in most member states against the constitutional advances of the ECJ, with a partial exception of Netherlands and Luxembourg. Until the mid-1980s, the member states carefully guarded national markets against a possible negative impact from the Common Market through various administrative means. Despite the advances in ECJ case law on market liberalization, national administrations systematically tried to circumvent European law when it was inconvenient to social and economic national interest (Pedersen, 2016). National courts likewise did not warm easily to the new ECJ and European law. Although the traditions for receiving international law in certain countries such as the Netherlands and Belgium made courts in those countries more open to the influence of European law, most national courts were slow adapters. Traditional prejudices against the influence of international law in the national constitutional order as well as a strong resistance toward judicial review, implicit in the preliminary reference mechanism, in certain countries created a strong reluctance in many courts to use European law. The impression emerging from historical studies confirms the strand of political science literature that has emphasized how member states “contain” European law also in more recent decades. (Conant, 2002; Martinsen, 2015) Finally, several courts of last instances in Germany, France, Italy, Britain, and Denmark were reluctant to accept the claim for autonomy of the ECJ implied in the doctrine of primacy. It was only when the major reform of the Single European Act and the plans for a single European market were carried out in the last half of the 1980s that national courts had to come to terms with the influence of European law. The single market in particular quickly obtained a status as the highest national interest of all the member states. As a result, the remaining skeptics among the courts of last instance now accepted the way the European legal order worked; however, at the same time the Conseil d’état in France as well as the constitutional courts of Italy and Germany made clear that the competences of the European construction were not autonomous, but merely delegated by the member states on basis of the national constitutions. All in all, we can say that the development of a constitutional practice in European law was not particularly well received by national administrations or by most national courts (Rasmussen, 2018).

Maybe it was this broader and deeper dissatisfaction with the constitutional case law of the ECJ that eventually led to a majority of national governments to oppose the codification of the constitutional practice and instead decide to limit its effects in the Maastricht Treaty. It should be mentioned that in parallel with the development of a constitutional practice in European law, the EC saw the rise of a strong intergovernmental pillar in the EC with the development of COREPER to help administer the public policies developed from the early 1960s onward (Knudsen & Rasmussen, 2008), the introduction of the national veto right in 1966, and the establishment of the European Council in 1975 (Mourlon-Druol, 2016). It was indeed this intergovernmental pillar that was confirmed and codified by the Maastricht Treaty. The EU thus did not become the big step toward a federal Europe, assumed by the ECJ in its case law and hoped for by the Delors Commission, but rather cemented the dominance of national governments. The proto-federal and constitutional legal order developed by the ECJ was not codified; instead, a complex stalemate developed where national governments and national courts accepted de facto the way European legal order functioned because it was a crucial underpinning of the single European market, while also rejecting the constitutional claim and ambition of the ECJ.


The new historiography on European law has produced several key insights, which, if taken together, offer a new understanding of the development of European law from 1950 to the early 1990s. First, it uncovered how closely related the constitutional interpretation of European law that broke through with the Van Gend en Loos and Costa v. ENEL judgments were with the federalist ambitions of the European Commission led by Walter Hallstein in the first half of the 1960s. By doing this, some of the suspicions first brought forth by Hjalte Rasmussen were finally documented and confirmed. To interpret European law in a constitutional manner constituted an important step toward federalizing the EC and also helped consolidate the competences and autonomy of the supranational institutions. Although clearly the role and professional interests of jurists in building a legal foundation for the European construction mattered, as demonstrated by the new sociological research (Bailleux, 2014; Vauchez, 2015), historiography rather emphasizes the role of federalist ideology and the self-empowerment of the supranational institutions as central.

Second, a fully developed constitutional practice in European law, constituted by a proto-federal constitutional legal order and a legitimating constitutional discourse, developed because of the continued efforts of an alliance of the three supranational institutions from the 1960s to the 1980s. This was aided by pro-European judges and lawyers through the preliminary reference mechanism, as well as by an emerging academic field of European law that in the 1980s developed an openly constitutional discourse about the nature of European law. This stands in clear contrast to the most important social science theories that explain constitutionalization as a result of litigation of big firms, or emphasize the role of lower national courts.

Third, national governments, administrations, and courts were more hesitant about their acceptance of the constitutional practice of European law than generally believed, even if differences existed between the member states. Here historians have confirmed the strand of social science research that has emphasized how member states are able to contain European law (Conant, 2002; Martinsen, 2015). We now know that the general inaction of the national governments was caused by a stalemate in the Council of Ministers with regard to the ECJ and the constitutional practice of European law. The governments could not agree to intervene against the ECJ, nor could they agree to codify the key doctrines of the constitutional practice. The inaction consequently did not, as Weiler has argued, constitute an implicit acceptance of the development of a constitutional practice. The result gave the ECJ important room to maneuver; it did not have to fear any intervention from the national governments collectively. In the end, however, the constitutional practice was not codified and accepted by national governments and the member states in the Maastricht Treaty. The constitutionalization of European law thus could not obtain the general breakthrough for a federal understanding of the European construction that political attempts for federal reform had failed to achieve from the 1950s onward. Full constitutionalization of European law did not succeed by the early 1990s, as has been claimed in particular by the social sciences, but also mainstream legal studies.

The defeat of the Constitutional Treaty by referendum in 2005 repeated this defeat. Today the EU is certainly based on a legal order that looks and very much works like a proto-federal and constitutional legal order backed by an academic discourse and the supranational institutions that promote the constitutional claim of the ECJ. However, at the same time European law has not experienced a constitutional moment where the constitutional nature of the EU has been politically endorsed by the electorate or the national governments. Nor is it possible to say with certainty that a point of no return has developed if we believe full constitutionalization can happen gradually from “below.” In fact, the EU has in many respects seen a parallel strengthening of state power, new intergovernmental methods of coordination, and Euroland rules that cannot easily be understood through the lenses of constitutional law (Bickerton, Hodson, & Puetter 2015). The new historiography on European law thus offers a new understanding of how European law has developed since 1950 that undermines well-established truisms of European studies and opens up a new debate of just how the European Union has developed these last 25 years.


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