Adapting to the rigours of European integration has been one of the most transformative forces on the post-war nation state. While obvious in the realm of politics and economics, it is equally valid for the legal sphere as well. By the early 1950s, most of the original six member states had initiated constitutional reforms preparing for an unprecedented transfer of competences to European institutions.Footnote ¹ The long-term consequences of these reforms are yet to find much reflection in historical research. The importance of national constitutional law has been at best reduced to the question of whether member states followed a monist or dualist regime in the application of international law.Footnote ² Only recently has there been more understanding of the influence of post-war constitutions on the process of forming the European legal order.Footnote ³ For instance, Peter Lindseth's recent history of European law focuses on the transfer of elements of the post-war administrative state to the legal construction of Europe, with the concomitant loss of democratic accountability and legitimacy.

This article similarly seeks to incorporate national constitutional traditions into the construction of Europe. By exploring the highly pertinent case of the Netherlands, it reveals the complexity and mutuality between national constitutional reform ‘towards’ Europe and the development of European integration in the 1950s. The constitutional reforms of the Netherlands in 1953 and 1956 would not only define the conditions of Dutch membership of supranational organisations, they would also controversially introduce the notion that international treaties, law and jurisprudence should have priority over conflicting national legislation, even of a later date. This article explores the political and ideational context of the crucial Dutch reforms through an examination of the work of several constitutional committees in the Netherlands from 1950 to 1956, using primary sources for the first time. These committees, representing a cross-section of the Dutch political and legal elites, advised the government on constitutional reforms suitable for enabling participation in Europe, among other issues. Hence both their internal discussions and the broader debates that followed are most revealing about how the Dutch approached European integration and its legal ramifications. The article is structured around the themes of those debates, which include, first, the democratic structure of European governance, second, the relationship between national sovereignty and European integration, and third, the binding force and primacy of European law.

This article confirms the validity of Lindseth's focus on the administrative state, but also moves beyond, demonstrating that multiple other influences, not least longer-standing Dutch traditions of adherence to international law, played a crucial role in Dutch legal discourse. The rich texture of national constitutional law has been thus far ignored or underplayed, vastly limiting our true and full understanding of this crucial period in the history of European law. In fact the consequences of the Dutch constitutional reforms would loom large both in the history of European law and in the political and legal landscape of the Netherlands. In European law, the reforms paved the way for an early wave of preliminary references (Article 177 EEC) to the European Court of Justice (ECJ). Eight of the first eleven referrals were Dutch. The second of these asked the crucial question of whether Article 12 of the EEC Treaty had direct effect, which led to the famous Van Gend en Loos ruling by the ECJ with which the constitutional practice was launched.Footnote ⁴ In the Netherlands, the constitutional reforms became part of a longer tradition of viewing international communities as new legal orders with some sovereignty of their own. As a result, legal and political elites tended to ignore the growing resistance to the integration process in Dutch society until alerted to this by the defeat of the European constitutional treaty in 2005.Footnote ⁵

Democratic concerns and administrative solutions: the Van Eysinga CommitteeFootnote ⁶

In May 1950 – ten days after the French foreign minister, Robert Schuman, announced his plans for a new European Coal and Steel Community (ECSC) – a ‘Committee concerning the co-operation between government and parliament with regard to foreign affairs’ was inaugurated in The Hague. As the first of three committees expected to recommend constitutional reforms, it was tasked with clarifying the role of parliament in Dutch foreign policy, particularly in the ratification of treaties, and the mechanisms through which parliament was informed on foreign affairs.Footnote ⁷ The committee constituted a direct response to a recent debacle over a Benelux treaty in 1949 on the harmonisation of duties.Footnote ⁸ The treaty infringed upon the parliament's budgetary powers, yet had to be ratified with haste in order not to hamper the government's decisiveness in later negotiations. It was therefore illustrative of how increasing European co-operation compelled a new relationship between the executive and the legislature in foreign policy formation. As a result, the Dutch parliament became increasingly interested in sharing, in one way or another, the ‘government prerogative’ in foreign policy. Conversely, the Dutch government stood firm on its position of keeping parliament out of what it considered highly delicate negotiations.Footnote ⁹ The Dutch constitution traditionally left the government plenty of room to conclude and ratify treaties, designating only some categories for parliamentary ratification.

The constitutional committee met for the first time in May 1950 against this contentious backdrop. Committee chairman W. J. M. van Eysinga, a professor emeritus of international law, had already recommended in his 1906 doctoral thesis that the role of parliament be enhanced in the area of treaty ratification.Footnote ¹⁰ Yet, at the first committee meeting, Van Eysinga emphasised that modernisation of these constitutional clauses also had to serve the government's interests. He argued that, given the growing prevalence of regulating international relations by treaty, the ratification procedure hindered an efficient foreign policy, particularly when the treaties were of minor importance or required ratification in a short period of time. He suggested, as a general rule, that all treaties should be submitted for parliamentary approval, but the possibility of a ‘tacit’ approval by parliament would offer the government the leeway needed to conduct its foreign policy efficiently.Footnote ¹¹ This innovative approach, in which parliament was allowed thirty days to demand a ratification debate before a treaty was ratified tacitly, would eventually constitute the key result of the committee's 1950 report on constitutional reforms.Footnote ¹² Due to his historical authority on this matter, Van Eysinga found full support for his compromise at the very first committee meeting.Footnote ¹³ Given this support in the committee, the government followed Van Eysinga's recommendations in its 1951 constitutional amendment bill. Nonetheless, a number of changes had crept into the legislation. There was, for example, the inclusion of a new rule for exempting a treaty from parliamentary approval under the rather vague category of ‘urgent cases of an exceptional nature’, needed in order to safeguard executive authority.Footnote ¹⁴ These changes were heavily criticised in parliament, which only consented to the new procedure after it had restricted the exceptions by amending the bill.Footnote ¹⁵ Eventually, the new principle of tacit parliamentary approval was included in the 1953 constitution.

The tacit approval procedure is very similar in practice to the oversight principle in delegated law-making distilled theoretically by Lindseth in his research on France, Germany and Italy.Footnote ¹⁶ Parliament would – with the restriction of not participating in the negotiations directly – be allowed to participate in the ‘legislative’ process of treaty making. When it chose not to, it delegated authority to the government to do the often highly specialised and technical work on its behalf. There are other parallels between Lindseth's model and the Van Eysinga Committee's findings. Its recommendations on government–parliament co-operation, for instance, included suggestions to strengthen parliament's right to be informed on foreign policy and to enhance the participation of MPs in delegations to international conferences.Footnote ¹⁷ Essentially, strengthening parliamentary oversight merely followed administrative law practices that had been on the rise in the Netherlands since the 1920s. Yet, this oversight model clearly broke with the traditional form of parliamentary democracy employed in the Netherlands, in which a combination of strong Royal cabinets and a separation of powers had resulted in a clear emphasis on the independent and separate positions of the legislative and the executive.Footnote ¹⁸

Although practices from the administrative state model were eagerly adapted, particularly the delegation of highly technical work, this traditional model of parliamentary democracy still served as an important archetype in Dutch political and scholarly debates on Europe.Footnote ¹⁹ Clearly, a similar parliamentary style government did not yet exist at the European level. The Van Eysinga Committee's final report predicted that a powerful federal European structure was needed to make up for the loss of democratic control incurred at the national level in transferring sovereignty to this new European regime. Without giving important decision-making powers to the European institutions, comparable to the federal governments of the US or in Germany, they ran the risk that these institutions could become insignificant, much like the Council of Europe's (COE) council of ministers. As this executive had very little real power, accordingly the COE general assembly also failed to meet the standards of national parliamentary governance, since it had nothing worthwhile to oversee and control.Footnote ²⁰ However, the new ECSC Treaty included the promise of a real and powerful supranational executive (the High Authority) and a parliamentary body (the Common Assembly) to control it. Therefore, the committee recommended the establishment of close co-operation between the parliamentary assemblies of the ECSC and the COE – a suggestion one committee member, MP and Strasbourg delegate M. A. M. Klompé, would afterwards repeat in the COE general assembly.Footnote ²¹

The committee however recognised that the ECSC fell short of establishing a real European federation. Instead, the committee turned to more short-term, pragmatic suggestions. It argued that, as long as one ‘European people’ did not exist, the democratic structures at national level should continue to ensure the accountability of the European institutions. Inspired by a meeting with several Dutch delegates to the 1950 COE general assembly, the committee suggested that, rather than building a federation by constitution, the states and their electorates would have to grow together gradually.Footnote ²² Thus, the committee recommended that integration in limited functional areas, such as in the Schuman Plan, should be used to bring a ‘series of practical steps forward’ on the road to federalisation. This functionalist path sat well with both the preferences of Minister of Foreign Affairs, D. U. Stikker, and with the dominant political ideologies in the Netherlands: social democratic functionalism, Catholic subsidiarity and Calvinist ‘sphere sovereignty’ all found elements familiar to their ideals in it.Footnote ²³ Yet, the committee realised that the functionalist path to a federal Europe threatened to fulfil the committee's own concerns about the democratic harm inherent in such a technical form of administrative management. As a result, the Van Eysinga Committee recommended that during the ‘functionalist’ phase of integration, democratic oversight should remain in the hands of national parliaments, controlling and limiting the transfer of competences to the new organisations.Footnote ²⁴

Shortly after the Van Eysinga Committee presented its report in July 1951, initiatives for a European Defence Community (EDC) and a European Political Community (EPC) appeared, promising a further step on the road to federalisation. These prospects, as well as the recent ratification of the Treaty of Paris, deeply influenced the parliamentary debates during 1952 on the constitutional amendment bill.

The bill, besides introducing the new democratic procedure for treaty ratification mentioned above, also presented new provisions on the interaction between the Dutch and international legal orders. The new provisions resembled those already found in the new constitutions of France, Germany and Italy. The German Grundgesetz, for example, authorised the federal state to transfer sovereign powers to (similarly democratic) international organisations, whereas the French 1946 constitution and the Italian 1947 constitution stated that national sovereignty could be limited when needed for the organisation and defence of peace. Separately, Belgium and Luxembourg undertook similar constitutional reforms aimed at preparing their national constitutions for the expansion of international and European co-operation.Footnote ²⁵ However, only the Dutch gave so much importance and authority to international law. The Dutch 1953 constitutional reform not only fully authorised the transfer of legislative, administrative and judicial competences to international organisations (Article 67Footnote ²⁶), but also, when ‘demanded by the development of the international legal order’, allowed for the ratification of treaties found deviating from the constitution (Article 63Footnote ²⁷). This unique reform was inspired by a long-standing Dutch legal doctrine on international law, which will be further explored below.

National sovereignty and supranational organisations: the Van Schaik Committee

In June 1950, Strasbourg delegate and MP for the Dutch Labour Party (Partij van de Arbeid: PvdA) G. Ruygers began openly to discuss, on basis of the present constitution, the extent to which the Netherlands could subordinate itself to the European institutions under construction.Footnote ²⁸ Ruygers, a known champion of the European cause, envisaged a constitutional reform to prepare for the wholesale transfer of sovereignty to a united Europe. The radical nature of his vision immediately caused suspicion among the other political parties. For confessional and liberal politicians, Ruygers’ ideas on Europe reflected his social democratic belief in an all-present state, whether at the national or at the European level.Footnote ²⁹ Yet, the underlying notion that a constitutional provision on the transfer of competences was required did find resonance outside social democratic circles. Most parties supported European integration and, more specifically, the ECSC, which was under negotiation at that time.Footnote ³⁰ Ruygers’ call for constitutional reform however had indirectly shed significant doubt on whether national competences could be transferred to international organisations on the basis of the present constitutional framework.

To dispel this insecurity, two options were at hand. The first option, a reform of the constitution, was developed by a second constitutional committee active in 1950, the Van Schaik Committee. This committee, presided over by the special minister for constitutional affairs J. R. H. van Schaik, had been appointed in April 1950 and was responsible for the general modernisation of the nineteenth-century Dutch constitution. In direct response to Ruygers, the Van Schaik Committee decided to propose a new constitutional provision on international organisations, stating that competences could be transferred to ‘organisations of international law’.Footnote ³¹ Thereby, the committee both acknowledged the most recent developments in this field and pre-empted possible constitutional objections against Dutch ECSC membership from those politicians and organisations more critical of European integration.

Whereas the Van Schaik Committee opted for constitutional reform, the Van Eysinga Committee turned to older Dutch legal traditions for inspiration. As had also been noted by the Van Schaik Committee, from the perspective of legal precedent, a constitutional clause was not at all necessary for the transfer of competences to international organisations. Such transfers had already taken place in the early nineteenth century: the empowerment of the 1816 Central Commission for the Navigation of the Rhine with judicial authority on the river so crucial for Dutch trade, or the installation of the Permanent Court of Arbitration in 1899. In those cases, a constitutional provision had not been needed. The same applied to the transfer of often far-reaching decision-making authority to organisations such as the UN Security Council after 1945.Footnote ³² This precedent was supported by the fact that earlier proposals for constitutional regulation of such transfers had never found much support. In the early twentieth century, Dutch constitutional committees had discussed the constitutionality of these transfers, and although a special constitutional provision had been proposed in 1912, no reform had followed.Footnote ³³

Instead, Dutch legal scholars had followed a line of thought in the first half of the twentieth century in which international communities were perceived as new legal orders with some sovereignty of their own – and, by some, even as higher legal orders than the national one. This doctrine opposed standard jurisprudential thinking on international law, which argued that treaties were contracts between sovereign states with the implication that the acceptance of international law was conditional on all parties respecting the contract.Footnote ³⁴ This Dutch doctrine of ‘community law’ inspired the Hoge Raad, the Dutch Supreme Court, to embrace monism in 1906. As a consequence, the law of so-called ‘supranational communities’ could directly affect Dutch citizens.Footnote ³⁵ Moreover, the followers of the community law doctrine took a liberal stance towards national sovereignty. Perceiving international law as the law of a different legal order, they denied that this law could conflict with national law at all – not even when ‘constitutional’ competences were at stake. When a political controversy arose in the 1920s concerning a Dutch – Belgian treaty on the Scheldt river, a vital means of access to the port of Antwerp, the question as to whether the treaty was in violation of the constitution was dismissed by a majority of eminent constitutional law scholars, who stated that such a violation was not even possible.Footnote ³⁶

Despite this, the Van Eysinga Committee ultimately, after some wavering, agreed to the Van Schaik recommendation of a new constitutional clause that, in recognising the dramatic rise in international co-operation requiring a transfer of competences, would have important symbolic value.Footnote ³⁷ Meanwhile, the committee worried that the proposal for this new clause might ironically have a detrimental effect on the ratification of the ECSC Treaty, now that this was to be ratified before the new clause could be turned into constitutional law.Footnote ³⁸ Therefore, the committee, building on the very flexible Dutch way of dealing with its constitution,Footnote ³⁹ decided to add some extra lines to its recommendations: the Van Eysinga Committee report expected that – going back to the original question posed by Ruygers – a flexible understanding would develop of what could be considered ‘in line with the constitution’.Footnote ⁴⁰ Thus, the question of whether the transfer of competences to the ECSC was in line with the Dutch constitution would be left to the politicians after all.

In the following months, political support for the ECSC turned out to be strong enough to remove all doubt about the reconcilability of the constitution and the ECSC Treaty.Footnote ⁴¹ Yet, the plans for an EDC offered a new test. The possible merging of the Dutch army into a European army could easily have been considered a violation of the Dutch constitutional provisions on the organisation of national defence. This would mean that political opponents of the EDC could block the treaty by questioning its constitutionality. Although the government had included the Van Schaik proposal for a provision on the transfer of competences in its constitutional amendment bill, doubts arose as to whether this provision would allow for the transfer of competences specifically mentioned in the constitution. The government, supporting the EDC, asked the Van Schaik Committee for advice. After renewed discussions, a pragmatic solution was found in a special ratification procedure. This procedure, which could only be invoked ‘in the interest of developing the international legal order’, stipulated that treaties deviating from the constitution had to be ratified by a two-thirds majority.Footnote ⁴²

In parliament, neither this far-reaching provision nor the earlier provision on the transfer of competences faced much objection. A large majority accepted that government ‘needed’ them for an effective hand in negotiating international policy.Footnote ⁴³ This was legitimised by arguments about long-standing Dutch traditions in international law. MPs and government gladly reminded each other of Hugo Grotius or the 1922 constitutional clause on the peaceful settlement of conflicts through international law.Footnote ⁴⁴ Thus, without spending much time on questions of sovereignty or the original nature of supranational organisations, the Dutch introduced two ‘leading’ provisions in their constitution through which virtually any transfer of sovereignty to an international organisation could be approved.Footnote ⁴⁵

Setting the stage for Van Gend en Loos: Primacy and binding force

Driven by the same reading of the Dutch legal tradition that inspired the discussions on sovereignty and the transfer of competences, the constitutional reform of 1953 also produced provisions on the primacy and direct effect of international law that went far beyond the constitutions of other European countries. From 1953 onwards, the Dutch constitution stipulated in Articles 65Footnote ⁴⁶ and 66Footnote ⁴⁷ that international law bound Dutch citizens and companies without having to be transformed into national legislation (it was ‘binding on anyone’, or, as it would later be translated, it had ‘direct effect’) and that it should have primacy over contrary national legislation. In 1956, a subsequent reform limited this primacy to international law of a self-executing nature only, which meant that it directly addressed the rights and duties of citizens.

In the Van Eysinga Committee, the new primacy provisions had merely been a side issue to the main question about the new ratification procedure. Van Eysinga, who himself would first design the provisions, held that both primacy and direct effect were already part of Dutch legal practice. Indeed the Hoge Raad had already acknowledged that international law could bind individuals in 1906 – a step also taken elsewhere, for example in Belgium in 1925.Footnote ⁴⁸ At the time, the Hoge Raad however did not settle the question of whether international law had primacy over conflicting national law. This question would be heavily disputed in the inter-war period. At the 1937 annual meeting of the Dutch lawyers association (Nederlandse Juristenvereniging: NJV), only a small majority of prominent legal scholars voted in favour of the proposition that treaty law ‘binding in the national sphere’ should be given priority over national law whether antecedent or subsequent.Footnote ⁴⁹ The Hoge Raad avoided adjudicating on the matter and kept to ‘interpreting away’ any possible conflict between treaty law and posterior national legislation.Footnote ⁵⁰ Only its temporary partner, the High Court on Special Justice Concerning the Second World War (Bijzondere raad van cassatie), recognised the supremacy of international law in a 1949 ruling.Footnote ⁵¹ This ruling however did not end discussions on general Dutch practice.Footnote ⁵²

Despite the split doctrinal opinion and the unclear practice, Van Eysinga argued in his 1950 proposal that he only intended to lay down what had already been settled in Dutch doctrine. To do so, Van Eysinga was shrewd enough to address the major concerns of the opponents to primacy in the 1937 NJV meeting. His proposal thus demanded that only published treaties could be ‘binding on anyone’: the provision intended to safeguard Dutch citizens from being bound to obey rules which they could not know.Footnote ⁵³ Although the other committee members realised that this might not appease all opponents, they nevertheless supported the proposal.Footnote ⁵⁴ Apparently, Van Eysinga managed to convince the committee with his claim that the French 1946 constitution also acknowledged the primacy of international law.Footnote ⁵⁵ Similarly, a subcommittee to the Van Schaik constitutional committee also accepted this clause as self-evident, stressing the primacy and independent nature of international law to an even greater extent. Footnote ⁵⁶

While the primacy provision found its way into the reports of the Van Eysinga Committee and the Van Schaik subcommittee, it met resistance in the Van Schaik plenary committee. Committee member and constitutional law professor G. van den Bergh supported the principle of primacy in general, but objected to the insertion of an article granting the primacy of treaty law over subsequent national law in the constitution. In the Dutch system, Van den Bergh argued, the constitution deliberately allocated the final interpretation of statutes to the legislator, not to the judiciary. To Van den Bergh, this principle, which had been laid down in the constitutional ban on judicial review of statutes since 1848, represented the essence of Dutch democracy.Footnote ⁵⁷ These objections mirrored the concerns of the 1937 opponents and foreshadowed similar concerns that blocked constitutional reform in Belgium in 1953.Footnote ⁵⁸ Initially, Van den Bergh could not convince any other committee members to side with him. In the July 1951 interim report, however, he found three prominent committee members – all (future) professors of constitutional law – on his side: L. J. M. Beel, soon to be minister of internal affairs; P. J. Oud, leader of the liberal parliamentary group; and A. M. Donner, future president of the ECJ. The latter suggested leaving this matter undecided as long as ‘doctrine’ did not agree on this inconsistency.Footnote ⁵⁹

Although the new constitutional provision on primacy still had the support of a large majority of both committees, the government decided to leave the contested clause out of its constitutional amendment bill. In particular, Prime Minister W. Drees rejected the primacy provision, fearing that the legislative would be powerless against a judicial interpretation of a treaty which, as he put it, in the case of [a small country like] the Netherlands, might not always fit the intended results of the original negotiations.Footnote ⁶⁰ In parliament, the two largest parties in the government coalition, Katholieke Volkspartij (Catholic People's Party; KVP) and PvdA, criticised the absence of the primacy provision – finding the support of many legal scholars.Footnote ⁶¹ Consequently, P. J. S. Serrarens, the KVP MP and leader of the Dutch European Movement, who would also soon become Dutch judge at the ECJ in Luxembourg, handed in an amendment to the government bill which reintroduced the primacy provision.Footnote ⁶²

The Serrarens amendment was defended primarily as a political choice. Serrarens explained how earlier frameworks of international co-operation had failed not because they lacked good intention or design, but because they lacked proper enforcement. Since the primacy of treaty law would also include the decisions of international organisations, Serrarens hoped that a constitutional provision introducing the possibility of enforcing these decisions could be the first step in strengthening international regimes.Footnote ⁶³ His enthusiasm for the European cause appeared to be shared by almost all his fellow MPs. Even the opponents of the amendment wrapped their concerns in support for a more uniform application of international law. Yet, with Van den Bergh, they objected to the consequences of the amendment for the balance of powers in the Dutch system. Van den Bergh's co-signatory P. J. Oud, for example, argued that the legislature, not the courts, would be the best guarantee of a consistent application of international law, as it met and co-ordinated regularly with its international counterparts.Footnote ⁶⁴ Serrarens responded by pointing out that the legislature might still ultimately choose to defend national interests, whereas courts were in theory impartial.Footnote ⁶⁵ Furthermore, supporters of the Serrarens amendment rejected comparisons with the clause on constitutional review: whereas the legislature was perfectly able to keep the Dutch constitution in mind when preparing new law, the vast amount of written and unwritten international law was an entirely different matter and thus new laws might – unintentionally – diverge from previous international arrangements.Footnote ⁶⁶

Eventually, the pro-Europeans won the vote in the House of Representatives, passing the Serrarens amendment with a forty-six to forty majority.Footnote ⁶⁷ Animated discussions in the Senate followed, where the government now chose to defend the new amendment in order to rescue the rest of the bill.Footnote ⁶⁸ By the spring of 1953, the obligatory second reading of the constitutional amendment was also finished. Thus, after three years of discussion on Dutch traditions and European ambitions, the provisions on the ‘anyone binding force’ and on primacy of treaty law were fixed in the constitution. However, the story of the Dutch constitutional provisions that would lay the groundwork for path-breaking ECJ jurisprudence did not end there. A small, but crucially important revision in 1956, portrayed as merely technical by the government, was still to come.

In fact, the ink of the 1953 provisions had barely dried when the first problems with the new ratification procedure came to the fore. Since the bill on the new procedure for tacit parliamentary approval had undergone several amendments before it was turned into constitutional law, the new procedure soon presented a ‘constitutional puzzle’ to parliament and government alike.Footnote ⁶⁹ Furthermore, the terminology and consequences of the new provisions on direct effect and primacy were questioned in scholarly discussions.Footnote ⁷⁰ Because a general revision of the constitution was already scheduled for 1956, the government decided to tackle these ‘technical’ problems by creating a new, third committee. The assignment of the new committee, led by the professor of constitutional and international law R. Kranenburg, precluded a wholesale reconsideration of the 1953 reform. Yet, the Kranenburg Committee eventually limited the 1953 reform by placing a crucial condition on the primacy of international law, namely that this only possessed primacy if it were of a self-executing nature.

Was this a check on the traditional openness of the Dutch legal order symbolised by the 1953 provision? The Kranenburg Committee claimed it was not, arguing it had followed an interpretation of the Serrarens amendment given by Beel, who now as minister of internal affairs defended the amendment in the Senate in 1952. Here Beel had argued that courts would only accept ‘anyone binding force’ when treaty provisions were ‘self-executing’.Footnote ⁷¹ The distinction between ‘anyone binding’ and non-‘anyone binding’ provisions, ruling out the possibility that citizens would be able to proceed against vague or indirect policy objectives, had been established in Dutch legal practice from 1821 onwards.Footnote ⁷² Further still, Beel had claimed that he expected Dutch courts to be reticent with regard to ruling on political issues.Footnote ⁷³ This expectation was well rooted in Hoge Raad traditions as well as in scholarly and political opinion on the role of the judiciary, as would be demonstrated during the ratification of the European Convention on Human Rights in 1954.Footnote ⁷⁴

Yet, the 1953 clause went far beyond this traditional restraint, as Van Eysinga immediately pointed out.Footnote ⁷⁵ Although it also employed concepts long known in Dutch legal tradition, the 1956 restriction was founded in a recently developed, more reticent attitude towards international law. On the side of government, this reticence appears to have been fuelled by the first experiences with ECSC High Authority's decisions, which appeared to be not entirely in Dutch interests.Footnote ⁷⁶ Also the parliament demonstrated a change of spirit that, while still accepting the 1956 constitutional amendment stemming from the Kranenburg report, probably reflected the disillusionment from the recent failure of the EDC/EPC plans. Moreover, when parliament did ask some critical questions, the government again revealed its flexibility by stating that a broader understanding of ‘self-executing’ would be possible in the future.Footnote ⁷⁷

Although the 1956 constitutional amendment limited the primacy of international law in the Netherlands, this provision would still produce quite considerable consequences for the development of European law.Footnote ⁷⁸ Now that the Dutch constitution stipulated the self-executing nature of treaties and decisions of international organisations in order for them to become binding in the national legal order, the question of whether European law was self-executing became a core question for Dutch courts. In a 1962 ruling, the Hoge Raad would explicitly call for references to the ECJ in order to clarify the ‘intention’ behind certain treaty provisions.Footnote ⁷⁹ As a consequence of this ruling – and of the initiative of a group of pro-European lawyers who decided to engage in a series of test cases – a ‘steady stream of Dutch preliminary references to Luxembourg’ emerged.Footnote ⁸⁰ The second of these cases, filed in the name of the Dutch transport company, NV Algemene Van Gend en Loos, provided the Luxembourg judges with the question as to whether Article 12 of the EEC Treaty, entailing a negative obligation to refrain from introducing new customs duties, was self-executing. When the ECJ ruled that it was, because the Treaties of Rome intended to create a ‘new legal order in international law’, their interpretation not only solved the conflict in the case in hand, but also established the principle of direct effect for all the European member states, even if, unlike the Dutch, their national constitutions had not known direct effect before.Footnote ⁸¹ Thus, a cornerstone of a European constitutional practice was laid.