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date: 27 October 2020

The Treaties of Rome

Abstract and Keywords

Together with the Treaty of Paris (1951), which established the European Coal and Steel Community (ECSC), the two Treaties of Rome (1957) were the founding treaties of today’s European Union. Of the two Rome treaties, the more influential proved to be that which created the European Economic Community (EEC), although many contemporaries expected the European Atomic Energy Community (Euratom) to acquire that role. As during all major treaty negotiations in the history of European integration, there were divisions of opinion among the six ECSC member states (Belgium, France, West Germany, Italy, Luxembourg, and the Netherlands) along and within national lines. In the end, however, their governments were able to agree on a complex package deal with various components. To reach this result, the work of two preparatory bodies, the so-called Spaak Committee and an intergovernmental conference set up by the foreign ministers of the six ECSC states, proved crucial. In addition, transnational actors and networks had a considerable impact on the Treaties.

The ultimate treaty texts reflected this trajectory of negotiations and the wider political context of the time. The Treaties of Rome were less supranational than the Treaty of Paris, and the three resultant communities were characterized by their hybrid nature: until the Merger Treaty of 1967, they shared some common institutions, such as the Parliamentary Assembly and the Court of Justice, while they had three independent executive bodies. Euratom, which focused on cooperation in the sphere of nuclear power, soon experienced institutional crises, and the same holds true for the ECSC. The EEC, in contrast, possessed greater powers and unleashed more significant dynamics and thus became the core of European integration.

On the basis of the Treaties of Rome, the European Communities incrementally turned into the foremost forum of international cooperation and integration in (Western) Europe. That, however, was quite unclear in 1957, as reflected in opinion polls at the time. Moreover, there were important contenders for this role. By the end of the Cold War, the EC had outpaced them all, for three main reasons: its focus on market integration, its greater legal integration in comparison to organizations such as the Organisation for Economic Co-operation and Development (OECD) and the Council of Europe and, finally, its financial resources. In sum, one needs to know about the Treaties of Rome and the integration dynamics they unleashed in order to understand the enormous importance that today’s EU has acquired.

Keywords: European Economic Community, Euratom, European integration, common market, European Union politics, transnational actors


Along with the 1951 Treaty of Paris, the 1957 Treaties of Rome were the founding treaties of today’s European Union (EU). Together, they defined the key institutional, legal, and administrative parameters of the European communities, as well as their potential prior to the Maastricht Treaty of 1992. The stipulations of the Treaties were flexible enough to allow the European Community (EC) to venture into new policy areas and modes of governance beyond its original focus and official legal framing. While the post-Maastricht EU acquired considerable powers in fields such as monetary policy, justice, and home affairs, as well as foreign and security policy, inroads into these policy domains had already been made long before the 1990s, mostly in the context of the European Economic Community (EEC), one of the two Rome organizations. Given the high level of path dependency of many EU policies and institutional arrangements, even developments in our own time cannot be fully understood without taking into consideration the Treaties of Rome and the dynamics that surrounded them.

State of the Art

Research on the Treaties of Rome had already taken off during the 1960s. Throughout those first decades, it was mostly legal scholars and political scientists who analyzed the negotiations, their effects, and the implications at normative, political, and practical levels. The Treaties of Rome also featured prominently in some of the most eminent theories about European integration, including liberal intergovernmentalism and to some extent neofunctionalism (e.g., Haas, 1958, especially pp. 301–313; Moravcsik, 1998, pp. 86–158). The span of these approaches demonstrates that the Treaties’ histories hold more than one lesson and that, for many theories, they serve as a major test case.

With the opening of the relevant archives, beginning in the 1980s, historians started to join the conversation. Since then, a lot has been published. Several multilingual edited volumes deserve particular mention, covering the Treaties of Rome and their implications from various vantage points (Serra, 1989b; Trausch, 1993). Moreover, the Treaties figure prominently in The European Rescue of the Nation-State, the most influential attempt by a historian to theorize European integration (Milward, 2000). The Treaties’ 50th and 60th anniversaries sparked further interest, by historians as well as other scholars (e.g., Gehler, 2009; Maduro & Azoulai, 2010; Preda, 2013; Tilly, Welfens, & Heise, 2007).

To this day, the EEC is much more extensively researched than Euratom, on which comparatively little has been published, even if existing studies have demonstrated that European research policies, as they have emerged since the 1960s, drew substantially from Euratom’s construction and experience (Dumoulin, Guillen, & Vaïsse, 1994; Krige, 2016; Skogmar, 2004; Södersten, 2018). This trend to sideline Euratom is also reflected in recent syntheses of European integration history (e.g., Dinan, 2014a, 2014b; Gilbert, 2012; Loth, 2015), highlighting the EEC’s greater salience and its more dynamic character. Having said this, the state of the art also creates opportunities for future research, especially on Euratom.

While earlier accounts sometimes had strong normative biases—for instance, of a federalist (Pistone, 1999) or a Euro-skeptic nature (Booker & North, 2003), a lot of recent research emphasizes the open-endedness, complexity, and historical texture of the events and processes surrounding the Treaties of Rome. Most recently, the field has turned into a more constructivist direction, for instance, toward the analysis of ideational motivations and the Treaties’ role in narratives of European integration. The field is thus moving from an assessment of the Treaties of Rome themselves to also include (later) perceptions by scholars, the media, and other groups (e.g., D’Ottavio, 2019; Gilbert, 2009; Patel, Sianos, & Vanhoonacker, 2018; Phinnemore & Warleigh-Lack, 2009). In contrast to political science literature, historical research has remained emphatically multilingual, with only a minor tendency to prioritize English as a publication language, as reflected in the references of this article.

The Road to Rome

The road leading to the Treaties of Rome was comparably short but full of twists and turns. Even before Belgium, France, West Germany, Italy, Luxembourg, and the Netherlands successfully concluded the Paris Treaty, they began discussing new projects. However, the highly ambitious plans of the original six ECSC (European Coal and Steel Community) member states to establish a European Defense Community (EDC) and a European Political Community (EPC) had to be aborted in 1954: On August 30, the EDC Treaty failed to obtain ratification in the French parliament. The EDC and EPC would have greatly enhanced the integration process. The EDC would have lifted it to a level of vital importance, namely, security, while the EPC would have provided an overarching framework for sectoral and other more specific integration efforts. Measured against these plans and expectations, the two communities established with the Treaties of Rome in 1957 remained minor and focused on much more mundane issues.

Against the backdrop of the 1954 debacle, the Treaties of Rome represented the result of a steep learning curve: it had become clear that strong political forces in various member states were not ready to surrender core aspects of state sovereignty. Conversely, others thought that the Paris Treaty did not provide an economic and political basis stable enough for Western European cooperation, while some even dreamed of a political federation for which the ECSC would serve as the first stepping stone. The pro-integration camp therefore went on pushing for new initiatives, building on shared ideational motivations and transnational networks. Between December 1954 and April 1955 alone, some 50 proposals were aired to give the European project a fresh boost. Characteristically, these ideas were less ambitious than the EDC and the EPC, tending to focus on initiatives in the fields of “low politics,” such as transport and energy.

Particularly active in advancing new proposals and facilitating debates were top politicians from the Benelux states, such as Paul-Henri Spaak, at the time Belgian’s foreign minister, along with Johan Willem Beyen from the Netherlands and Joseph Bech from Luxembourg. Meanwhile, Jean Monnet continued to play a vital role in the French context, just as he had done in the run-up to the ECSC. Transnational elite networks with their informal meetings as well as the idea that an ever closer union was needed to face Western Europe’s challenges drove these debates (Dumoulin, 2017; Gerbet, 1989; Krüger, 2003, pp. 367–417).

First negotiations at a conference in Messina in June 1955 proved difficult, but, in the end, the six governments agreed that further steps of European integration were to be taken. To that end, they established a committee to which the British government was also invited. Negotiations were conducted in two different formats. First, during a phase from July 1955 to April 1956, they took place in the so-called Spaak Committee, an informal group of government delegates and experts who were not bound by the position of their respective governments. After this committee had presented a report summarizing its findings, the process was lifted to the more official level of an intergovernmental conference from July 1956 onward (Dumoulin, 1989; Gilbert, 2012; Küsters, 1982, pp. 135–268; Loth, 2017; Serra, 1989a).

Two formative developments took place during these 21 months of intense negotiations. First, the United Kingdom soon pulled out. Economically, it saw little attraction in a form of integration with a common external tariff since this seemed impossible to reconcile with the UK’s global trade links, most importantly with the Commonwealth. The British government also opposed the supranational approach preferred by the six ECSC states, partly for ideational, partly for practical reasons, and it argued that the whole scheme was unrealistically ambitious and lacked parliamentary control. The British government did not just withdraw its representative from the Spaak Committee in November 1955; it also tried to torpedo the debates among the six and soon came up with an institutional alternative revolving around less binding forms of economic cooperation. This course culminated in the 1960 establishment of the European Free Trade Association, a direct competitor to the EEC (Milward, 2002; Young, 2002).

Second, the six ECSC states agreed to reduce and reorganize the broad agenda of possible sectors and sites of European integration that the Messina conference had concluded with. Efforts now focused on two main topics: the creation of a common market and the peaceful use of atomic energy. In both cases, the member states agreed to push the possibilities of integration by creating communities with strong supranational traits. Other policy domains were also mentioned, such as agriculture and transport. Here, negotiations proved to be very difficult, and no clear consensus was reached. However, the Spaak Committee decided not to remove these items from the agenda; instead, they were left deliberately vague and integrated into the plans for the common market. This approach also shaped the travails of the intergovernmental conference and the final Treaties, and it combined visionary goals with consensus-oriented compromises. The six governments thus opted for a mixed approach: whenever the negotiating parties were able to agree on something, the stipulations were as precise as possible; on all other issues, they remained consciously ambiguous. Thus, there was no overarching concept dictating which areas the new communities should concentrate on. Instead, their foci emerged from the official negotiations supported by informal transnational contacts, for instance among Christian Democratic party elites. Without this dose of pragmatism, the Treaties of Rome would never have materialized (Loth, 2015, pp. 36–62; Roy, 2012, pp. 52–60). The way to their conclusion was full of crises; in July 1956, for instance, the West German government for some time thought that the EEC project had no chance of being realized (KPBR, 1956/1998, pp. 489–492). All in all, the road to Rome was far from straight.

Priorities, National Positions, Transnational Actors, and Public Reactions

The Treaties’ full historical significance was not clear in 1957. To start with, there was no consensus on which of the two endeavors mattered more. For the French government, Euratom was originally more attractive than the EEC Treaty, mainly due to France’s competitive advantage in nuclear energy with its potential links to military uses (Guillen, 1989). Generally, the 1950s were not just an era of increasing energy demand but also one of utopian expectations for nuclear power. At the time, some experts argued that civilian nuclear power was the key to solving all the great social and energy challenges of the future; furthermore, this was a field where energy and security concerns converged (Hecht, 1998). The treaty negotiations themselves were colored by the “perspective of a new industrial revolution far exceeding that of the preceding hundred years,” as the Italian foreign ministry noted.1 But, while many shared the enthusiasm about nuclear energy, not all saw this as a project with a European focus. The German government, for instance, was more interested in close cooperation with the technologically more advanced Americans and the British than in a French-led arrangement of the ECSC states. Such tensions help to explain why some of the original hopes associated with Euratom soon proved to be unrealistic—and why the EEC started to take the center stage among the three communities (Dumoulin et al., 1994).

Equally, the idea of the common market was controversial. It was first officially proposed by the Dutchman Beyen, who hoped to open new markets for the competitive Dutch export sector and to deepen European integration for political reasons too. From there, the idea found its way to the Messina conference and the next rounds of discussions. These negotiations proved to be rather difficult. France and Italy prioritized a high level of protectionism and planning, while the Benelux states and Germany preferred a more liberal approach, leading to intense conflict. Moreover, both Belgium and France insisted on creating close ties between the market project and their overseas colonies, whereas states without such an imperial dimension feared they would have to shoulder parts of the costs involved.

The EEC that resulted from these controversies is sometimes interpreted as a package deal between France and Germany. According to this interpretation, Paris wanted agricultural integration and Bonn (at the time the capital of the Federal Republic) wanted the Common Market—and each compromised in one field to achieve its goals in the other (e.g., Brunn, 2009, p. 116; Judt, 2005, pp. 305–306). Such accounts are simplistic and do not do justice to the complexity of the dynamics. In fact, Bonn was highly skeptical of the Common Market project. Given the country’s highly competitive industry, fears arose that the Common Market would become too protectionist and reduce Germany’s access to global markets. France, conversely, did push for agricultural integration, but so did the Netherlands. While the stipulations on the Common Market were comparatively clear and binding, those on agriculture remained much vaguer, which also qualifies the idea of the EEC Treaty as the result of a package deal. The same holds true for the follow-up negotiations after 1957. France and Germany were central players during this phase, but others also impacted the course of negotiations. For example, the EEC’s Commission now became a major factor shaping the trajectory of integration under its towering Commissioner Sicco Mansholt. Hence, Germany’s and France’s positions were more complex than the “horse-trade” argument has it, and this widespread interpretation underestimates the role of other important actors such as the Dutch government, transnational groups (see below), and the Commission.

In the end, all governments prioritized overriding political considerations over concrete economic and technological interests—otherwise, it would have been impossible to reach a result. Having said this, the two Treaties were so broad so that each of the six negotiating states found some specific points that made them economically attractive. Still, it is telling that, in a pompous ceremony on March 25, 1957, heads of state and government signed a stack of blank sheets: negotiations over a string of details had continued into the early morning of that day, so only the actual signatures were real (Küsters, 1982, pp. 432; Loth, 2015, pp. 62–74; Roy, 2012, pp. 52–60).

In sum, national economic interests were significant but should not be overestimated; broad political considerations, ideational motivations, and wider contexts were more important in all member states. Europe’s shrinking role on the global stage, the Cold War, and the idea of containing West Germany through integration were all important for the Treaties’ conclusion. Beyond these largely political motives, the wider context of the time mattered a great deal. The unparalleled postwar economic boom that had kicked in a few years earlier expanded the space for bargaining and made it easier to accept compromises. Other international organizations in Western Europe, such as the OEEC (Organisation for European Economic Cooperation) or the Council of Europe, did not fully satisfy the international coordination needs of the six ECSC member states. The Suez crisis of October 1956 demonstrated that France had lost a lot of its global leverage at a time when European colonial rule in Africa and elsewhere met increasing opposition. Taken together, these factors created space for further efforts toward European integration, while also putting existing policy approaches, such as imperial rule and less binding forms of European cooperation, under pressure.

The Cold War deserves particular mention in this context. The United States was not only Western Europe’s benevolent hegemon and supporter of postwar reconstruction (Lundestad, 2003); its government also enthusiastically supported efforts of European cooperation, not least to strengthen the Western camp in the East-West confrontation. Washington came out in favor of Euratom and the EEC, even though both projects entailed economic disadvantages from an American perspective. Secretary of State John Foster Dulles underlined the primacy of overarching political goals, and Washington was especially interested in the supranational component. Hence, the U.S. government did not interpret European integration as a challenge to the Atlantic partnership but as an integral feature (Giauque, 2002, pp. 19–33). This did not prevent many Western Europeans from seeing European integration as a means to counterbalance America’s overwhelming power.

In addition, the perception of the Soviet Union as a major threat to Western European security eased the search for workable compromises. In this sense too, the Cold War was deeply ingrained in the integration process. With his specific humor, Franco-German scholar Alfred Grosser once commented that really Josef Stalin deserved the first Charlemagne Prize for services to European integration: “Without that shared fear there would never have been a Community” (Grosser, 2002, p. 200). Concomitantly, the Treaties hardened the Cold War divide. In 1957, the Soviet Foreign Ministry argued that the EEC Treaty would lead to “further deepening of the division of Europe and heightening of tensions within Europe.”2 The EC’s attitude toward the Soviet Union was similarly critical, although in this context “Brussels” remained a great deal less influential than the member states and their respective foreign policies. Nevertheless, the EC’s capitalist orientation and close ties with the United States and NATO (North Atlantic Treaty Organization) served to deepen the Cold War divide (Domnitz, 2015; Faraldo, Gulińska-Jurgiel, & Domnitz, 2008; Schmidt, 2009).

To explain why the EEC and Euratom came into being, two further factors are paramount. First, beyond the governments of the six member states, other actors pushed for these new steps of integration. Jean Monnet, who increasingly turned into the gray eminence of European integration, played an important role brokering between the various sides; to that end, in 1955 he set up the so-called Action Committee for the United States of Europe, a high-level group of politicians and trade union leaders supporting European integration through informal networking. Other important transnational actors were business leaders interested in seeking access to new markets or, as a third example, transnational political networks such as those of Western Europe’s powerful Christian democrats. Behind the scenes, these professional transnational actors and pressure groups played an important role, sometimes spearheading, sometimes supporting or altering the positions of governments. Their work thus qualifies interpretations that exclusively focused on national interests (Kaiser, 2007; Kaiser, Leucht, & Rasmussen, 2009; Leucht, 2009; Ramirez Pérez, 2009).

Second, the civil societies of the six states need to be mentioned. In a nutshell, there was little enthusiasm about the Treaties of Rome, but also no stiff resistance. The pro-European civil society activism that had characterized the first postwar decade had already lost its momentum by the mid-1950s. Many media outlets reported approvingly about the signing of the Treaties of Rome, and some with great enthusiasm and sweeping praise. But reports frequently contained a healthy dose of skepticism, for example, in the Frankfurter Allgemeine Zeitung: “This is a grand decision. And if it turns out to be successful, it will be a grand achievement.”3 This was journalism in the optative: Wishes for the future abounded, but there was less optimism regarding the current state of affairs and achievements to date. Beyond broadsheet newspapers, the Treaties were by no means uncontroversial. For many on the political right, national sovereignty and often also the continuation of overseas imperial rule were deemed more important than European integration—or integration was only considered useful if it served as instrument for these other priorities. Western Europe’s far left also had other ideas. French and Italian Communists—who at times could rely on more than 20% of their respective national votes—critiqued the Treaties of Rome as a US-led capitalist conspiracy against the European working class and the Soviet Union (Cruciani, 2007). Writing about the Treaties of Rome, L’Humanité, the central organ of the French Communist Party, emphasized that “the United States is satisfied, the Vatican too.”4 From a communist perspective, a clearer way of condemning the Treaties was hardly possible. Having said this, ratification was easy in comparison to later EU treaties, since these opponents could not mobilize electoral majorities.

Against this backdrop, most people responded with disinterest to the Treaties of Rome. According to a survey in March 1957, the month the Treaties were signed, only 67% in Italy had heard of the “European Common Market”; in France, the figure stood at 64% and in West Germany at 62%. According to other opinion polls conducted two months later, knowledge of the existence of Euratom was 10% to 15% lower in each of the three countries (Bitsch, Loth, & Barthel, 2007; Gazzo, 1989; Rabier, 1989). Clear-cut support for this new attempt of European integration remained small—but outright opposition did not become prominent either. Most people simply did not care about the Treaties of Rome.

The EEC and Euratom as Hybrid Organizations

From its beginning, the organizations established by the Treaties of Rome were hybrids in several ways. Euratom largely followed the template of the ECSC’s focus on sectoral integration, in this case for the field of nuclear power. The EEC, on the other hand, possessed a broader mandate to establish a Common Market with free movement of goods, services, people and capital, and common external trade rules. Building on the work of the Spaak Committee, the EEC Treaty also contained stipulations about setting up other common policies, such as a Common Agricultural Policy (CAP) and a Common Transport Policy. Unlike the ECSC Treaty, where the rules had been spelled out in detail, the stipulations in the EEC Treaty tended more toward broadly couched powers. In 1957, this approach was instrumental to reaching a conclusion. However, it also had important implications that only became fully visible in the medium term. Whether a project under the banner of the Treaties of Rome, and particularly the EEC Treaty, would fly also depended on subsequent negotiations. The original hopes were realized in the case of the Common Market as the core project. The Common Market had already come into being after a process of three transitional phases by July 1968, 18 months ahead of the schedule stipulated in the EEC Treaty (Ambrosius, 2009). The sheer speed with which the Common Market project was accomplished was seen as a major success. Another achievement was the creation of the Common Agricultural Policy, also over the course of a mere decade. The fate of other projects was more mixed: the Common Transport Policy, for instance, did not get off the ground until the 1990s. The EEC’s wide legal approach opened up broad possibilities but also increased the risk of failure (Patel & Schot, 2011).

The organizations created by the Treaties of Rome also remained hybrids in other ways. The two newly created Communities were neither part of the ECSC nor completely separate entities. Each of the three organizations had its own Commission (the ECSC’s, just to complicate matters, was named the High Authority) and separate Councils of Ministers, comprising the relevant ministers from the six states. But they also shared a number of institutions, principally the Parliamentary Assembly and the Court of Justice. Particularly during the Communities’ early years, this complicated matters and led to competition over people, resources, and relevance between the three Communities (Palayret, 2001; Spierenburg & Poidevin, 1994, pp. 379–387). It was only the Merger Treaty of 1965 that brought them closer together, although without melding them entirely. This process created the “European Communities,” and while the executives of the three organizations were now merged, different rules continued to apply for the various Communities.

Even more important was another feature. The ECSC Treaty gave important supranational powers to the High Authority to propose, execute, and implement policies. By contrast, both the EEC and the Euratom Treaty chiefly provided a framework in which much depended on future legislation. Organizationally, the new treaties gave more power to the Council of Ministers. Thus, they were more intergovernmental than the Paris Treaty. Having said that, the EEC Treaty provided for an incremental expansion of majority voting over the various transitional phases, leading to the conclusion of the Common Market. Majority voting implies that a country can be outvoted, and that in the extreme case an overwhelming majority might override a vital national interest. The EEC’s voting modalities were thus based on a sequenced teleological timeline, according to which the Communities would incrementally shift to a more supranational logic of integration. The idea was to give the states some time en route to the “ever closer union” which the EEC Treaty’s preamble famously called for (Patel, 2018, pp. 289–292).

This program of the EEC Treaty was never fully realized, mostly because of French resistance. As a result, the Community remained more hybrid between the poles of supranationalism and intergovernmentalism than originally planned. On July 1, 1965, Charles de Gaulle’s foreign minister, Maurice Couve de Murville, announced the French government’s intention not to take its seat in the Council of Ministers until several problems in the EEC had been settled, and he famously recalled the French Permanent Representative in Brussels to Paris. France thus triggered the Crisis of the Empty Chair. Possibly the most contentious issue was the planned expansion of majority voting as of January 1, 1966. After six months of intense negotiations, in late January 1966, the member states reached the Luxembourg Compromise—an agreement to disagree. As an informal rule, member states could now exert a de facto veto in decisions when “vital interests” were at stake. The crisis was overcome and business as usual resumed—but the voting procedure had changed. So far, the rhetoric of federalism had loomed large, according to which the Communities would progress from being more intergovernmental in nature to being more supranational, toward the ultimate goal of federation. Now it had become clear that the hybrid character of the EC would remain a more permanent feature than ardent federalists, at least, had hoped (Ludlow, 2006, pp. 94–124; Palayret, Wallace, & Winand, 2006; Warlouzet, 2011, pp. 380–396).

The first decade after the Rome Treaties’ conclusion proved difficult in other ways too. The ECSC suffered from structural changes in energy and steel markets, to which it was unable to react effectively (Rasch & Düwell, 2007; Spierenburg & Poidevin, 1994). Also, Euratom did not turn into the dynamic platform of European integration that Jean Monnet and others had hoped for, at least not in the field of nuclear power. France pushed for a different technological approach than the other partners, and nuclear research could not be bundled in an efficient way. After the Merger Treaty, some of Euratom’s activities were redefined, and it increasingly became a forerunner to EC research policies and a venue for transatlantic debates about technology cooperation (Hubert, 2000; Krige, 2016; Skogmar, 2004). Even so, Euratom’s initial quasi-utopian hopes soon evaporated.

By comparison, the EEC’s dynamics were considerably greater. This was not just because of the creation of the Common Market within a decade, as mentioned above. Of almost equal importance was the EEC’s Common Agricultural Policy which soon developed into the EC’s most complex, costly, and controversial policy, absorbing considerably more bureaucratic energies than the Common Market for industrial goods. Beyond its obvious economic angle and sectoral focus, the CAP turned into a social policy in disguise that helped to ease the transition of the agricultural sector in the second half of the 20th century (Knudsen, 2009; Patel, 2009).

Market integration also led to legal dynamics that ultimately changed the character of the European Communities. Most importantly, several of the European Court of Justice’s (ECJ) rulings pertaining to the EEC had immense effects and pushed the whole EC far beyond the original remit of the Treaties. According to the original acquis communautaire, it was not clear that the EC would have a legal order overriding that of its member states—its stipulations could be read that way, but this was not clearly spelled out. That only changed with the ECJ’s van Gend and Loos judgment of 1963, which broke the accustomed bounds of international law. In 1964, Costa v. ENEL created the doctrine that gave EC law precedence over the laws of the member states. Ever since, European law has been able to override national law. And these were just two in a series of groundbreaking rulings which also reflected commercial interests and rise of EU law as a scholarly field supporting these decisions. Hence, the EC’s legal framework and an emerging field of concomitant expertise and interests unleashed their own dynamics that led incrementally to a legal order with constitutional aspects (Maduro & Azoulai, 2010; Nicola & Davies, 2017; Vauchez, 2015).

Other important developments have unfolded outside the official acquis communautaire. After some failed attempts to give the EC a foreign policy dimension in the 1950s and 1960s, the EC member states in 1970 introduced the European Political Cooperation (EPC) as a foreign policy mechanism. Though intended to strengthen the EC, the EPC had no foundation in the original Treaties; it was only formalized with the Single European Act in 1986 and further with the Maastricht Treaty. Similar things hold true for the European Summits, meetings of the heads of state and government of the member states which also commenced in the 1970s. The developments of the EC, as they unfolded on the basis of the Treaties of Rome, seemed to necessitate these new formats, even if they had no direct legal basis in them. Besides such institutional changes, whole new policy fields started to enter the EC’s agenda, including environmental and monetary policy along with home affairs. This also shows the high level of dynamism—and the incrementally increasing importance—that characterized the trajectory of the European Communities mainly thanks to the EEC. Having said that, other policy fields remained less prominent, including social policies, at least of the redistributive kind (Möckli, 2009; Mourlon-Druol & Romero, 2014; Patel, 2018, pp. 135–140).

Even if the EEC soon turned into the dominant forum among the three Communities, it did not immediately become the key venue for international coordination in Western Europe. In the early 1960s, there were still other important contenders, such as the Council of Europe or the OECD, and at the time it was unclear whether the latter might outpace the EEC as an international governance mechanism in Western Europe. The EEC’s towering role only emerged over time (Patel, 2018, pp. 22–64).

Why Foremost Forum?

Why, then, did the EC eventually manage to turn into the primary and increasingly also the dominant forum of regional cooperation and integration in (Western) Europe? Three factors stand out and, again, all three are mostly connected to the EEC (Patel, 2013; Patel & Kaiser, 2017).

First, the EC’s focus on a customs union and a common market (originating in the ECSC and even more in the European Economic Community) proved to be crucial in the long run. This economic logic produced many functional connections to other areas. Spillover effects from one policy domain to another were already recognized in the 1950s (Haas, 1958): the creation of the Common Market had repercussions in other areas such as hygiene standards, consumer protection, vocational training, and social policy. Research has long demonstrated that such spillovers did not happen quasi-automatically. What mattered more was that there existed groups and institutions—be they the Commission, the Parliament, transnational interest groups, or individual member states—insisting on supposed or actual inherent necessities and ready to pick fights to expand the powers of the EC. For example, in agriculture, once common market organizations existed for cereals, meat, dairy products, and vegetables, it was only a matter of time before the vintners, the olive growers, and even the flax and hemp farmers demanded similar arrangements (Ludlow, 2005; Patel, 2009). In each case the logic of the market raised questions that rubbed off on other policy areas, which then had to be accordingly promoted or constrained. This logic was also central for the EC’s expansion into policy domains such as environmental or monetary policy. The comparison to other forums is revealing. The Council of Europe, for example, was responsible for the vital matter of human rights. But in discharging this overtly political responsibility it found itself facing much greater resistance from its member states than the EC, with its economic focus and its more technocratic and seemingly apolitical attire. In view of the overwhelming predominance of the nation state as the model for political order, the “romantic” program of European cultural and ethical unification associated with the Council of Europe offered less spillover into other areas, or at least fewer actors successfully advocating such a course (Duranti, 2017). This was quite different from the economic logic of the European Communities.

Second, there was European law. The piecemeal emergence of a legal culture in its own right with a strong, binding character from legislation to implementation, gave the EC a great advantage over other Western European organizations. The latter were generally reliant on voluntary cooperation by their member states to implement broadly couched agreements into national law. In the EC, even ordinary citizens were able to appeal directly to the European Court of Justice under certain conditions, which was not the case with organizations like the OECD and the Council of Europe. This lent a specific dynamic to the ECJ and the development of law in the EC. At a very general level, the role of the ECJ was frequently decisive in expanding the powers of the EC, not least by a very broad interpretation of the market-driven mandate of the Treaties. The impact of European law—directly applicable and largely independent of the law of the member states—was the EU’s strongest weapon (De Witte & Thies, 2013; Nicola & Davies, 2017).

Third, and finally, the EC commanded larger financial resources than other Western European organizations. The OECD’s budget allowed for little more than funding its secretariat, a modicum of statistical research and a few expert commissions. Matters were little different for the Council of Europe. The EEC, by contrast, possessed revenues of its own from 1970, while the ECSC had enjoyed the same since the very beginning. This made the EC comparatively independent of its member states, especially where spending decisions lay largely with the Commission and the Parliament. The arrangement was hard fought for, but once in place it granted the EC a degree of freedom its rivals could only envy. Together, these three factors propelled the EC into a position of primacy among regional organizations in Western Europe (Patel & Kaiser, 2017).


This article has argued that many twists and turns characterized the trajectory leading to the creation of the Treaties of Rome and that their historical importance was far from clear at the time they were signed. From today’s perspective, it appears that without the Treaties, the cooperation of the six ECSC states would soon have lost momentum. But in 1957, it was unclear how dynamic European integration based on the Treaties of Rome would become. At the time, the Treaties were chiefly a declaration of future intentions for cooperation and integration. They provided the legal and administrative prerequisite and framework to this end which incrementally turned into a springboard for new initiatives. In the long run, the EC’s market focus and the binding character of its law, as well as its own resources, were instrumental for turning it into the dominant forum of European integration; hence, today’s EU still owes a lot to the Treaties of Rome.

Today, the Treaties of Rome belong to the very few instances in the history of the EU that are known to a broader audience and that are regularly referred to in the media. In fact, quality newspapers today often describe these Treaties as the genuine starting point of European union—a characterization that stands in contrast to most contemporaries who remained more ambivalent and frequently ignorant about the event’s significance (Patel, Sianos, & Vanhoonacker, 2018). Commemoration has even increased in recent periods in comparison to the postwar decades. The significance of the Treaties of Rome, along with the historically specific circumstances that led to them, thus emerge more clearly and are given greater space today than in their own times.


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(1.) Translated from DPII, 2017, p. 83.

(2.) Translated from “Regierung der UdSSR erklärt,” in Dokumentation der Zeit, ed. Deutsches Institut für Zeitgeschichte, Berlin (East), April 20, 1957.

(3.) “Die Unterschrift.” Frankfurter Allgemeine Zeitung, March 26, 1957, p. 1.

(4.) “Adenauer: Ces traites nous remplissent d’espoir,” L’Humanité, March 26, 1957, p. 1.