This study was requested by the European Parliament’s Committees on Legal Affairs and on Constitutional Affairs. It investigates national constitutional limits to further EU integration and explores ways to overcome them. It includes an in-depth examination of the constitutional systems of 12 Member States (Croatia, the Czech Republic, Estonia, Finland, France, Germany, Hungary, Ireland, Italy, the Netherlands, Poland, and the United Kingdom) and a bird’s eye view of all Member States. EU integration can be advanced by avoiding substantive constitutional obstacles in various ways. Overcoming the substantive obstacles requires managing national procedural constitutional hurdles. This is possible to the extent that the required broad political consensus exists.

AUTHOR(S) : Mr Leonard F.M. BESSELINK, Mrs Monica CLAES, Mrs Šejla IMAMOVIû, Mr Jan Herman REESTMAN.
This document is available on the Internet


1. The central research question of this study is whether, and to what extent, national constitutions provide guidance for further European integration and reversely how the latter can take place in full respect for national constitutional identities.

2. The research involved an in-depth analysis of a representative selection of Member States: Croatia, the Czech Republic, Estonia, Finland, France, Germany, Hungary, Ireland, Italy, the Netherlands, Poland, and the UK; and a bird’s eye view of all Member States. The study conducts a cross-national comparative analysis of the national constitutional approaches to EU integration, on the basis of which some final conclusions are offered.

3. This study deals with the relationship between the EU and national constitutions mainly from a national perspective. But there is also another side of the story, taking the EU perspective.
The EU Treaties (TEU and TFEU) acknowledge the central role of national constitutions, for instance when they require ratification by all the Member States ‘in accordance with their respective constitutional requirements’ for their entry into force, for their amendment and for the accession of new Member States. This presumably implies more than a mere procedural rule and acknowledges that the Treaties should also substantively be in accordance with national constitutions, or at least, it grants the Member States the opportunity, if their constitution so requires, to ensure that they do not enter into Treaties which would be unconstitutional.
On a more general level, the EU expects its Member States to comply with the common fundamental constitutional values that all Member States share, and which also apply to the European Union (Arts. 2 and 7 TEU). More specifically with respect to fundamental rights protection, the Treaty, the EU Charter of Fundamental Rights and the CJEU case law explicitly seek to connect EU human rights to the common constitutional traditions of the Member States. Yet, under the Treaties, the EU is not only bound to respect the common constitutional values of the Member States.
In addition, Article 4(2) TEU obliges the Union to respect ‘their national identities, inherent in their fundamental structures, political and constitutional, inclusive of regional and local self-government’.
Accordingly, if the Union should fail to respect these national identities as inherent in their fundamental constitutional and political structures, it would infringe not only those identities, but also the Treaty obligation to respect them. Whether this is indeed the case is, as a matter of EU law, to be decided ultimately by the Court of Justice of the Union, and not unilaterally by the Member States.
In addition, the Union must, under Article 4(2) TEU, respect the Member States’ essential State functions, including ensuring the territorial integrity of the State, maintaining law and order and safeguarding national security. In particular, national security remains the sole responsibility of each Member State.
The Treaty thus recognises that there are ‘essential State functions’ which remain with the Member States and which the EU must respect.
What exactly these functions are is not clear, beyond those mentioned in the provision.
On the other hand, and despite the central role of national constitutions in the EU constitutional edifice, Member States cannot invoke their national constitutions to escape compliance with EU law before the Court of Justice of the European Union. And even before national courts, national constitutional law should not, as a matter of EU law, take priority over conflicting provisions of national law.
Indeed, the principle of primacy of EU law,1 which is firmly settled in the case law of the CJEU, and has been confirmed in Declaration 17 annexed to the TEU, applies to national constitutional law as well. With respect to fundamental rights, more specifically, Article 53 of the Charter does not lead to a different conclusion.

4. Turning the perspective to national constitutions, it can be said that, in general, constitutions generally perform the four main functions of
* constituting the polity, which may be understood as expressing the basic social contract;
* organising and structuring the exercise of public authority and dividing powers between the various branches;
* limiting the exercise of public authority, which also includes fundamental rights protection of individuals and
* expressing common values of society and/or carrying its ‘national identity’.

As power-organizing tools, two of the main functions of constitutions go in different directions.
One is the enabling function of constitutions: constitutions constitute the institutions which are to exercise public authority and empower these institutions.
A second function is associated with ‘constitutionalism’ in a narrow sense and concerns the limiting function of constitutions: constitutions limit the exercise of public authority, for instance via human rights and a division of powers.
These different functions of a constitution are also reflected with regard to EU integration: national constitutions help to enable, and limit.

5. In the context of participation in the EU, the enabling function of constitutions is illustrated by those constitutional provisions which allow for a ‘limitation of sovereignty’ or a ‘transfer of sovereign powers’ to the EU.
However, national constitutions not only enable, but also set limits to further EU integration.
Membership of the European Union challenges the national constitutions in various ways: powers, which under the constitution have been attributed to national bodies, are transferred to the EU, and hence they are exercised differently from the way it was intended under the national constitution.
The EU is, as such, not bound by those national constitutions, but does indeed require the Member States to apply EU law even if it should infringe the national constitution.
Accordingly, the supremacy of the Constitution itself is challenged.
Seen in this light, it should come as no surprise that many Member States, while having adapted their constitutions to allow for membership and facilitate it, have at the same time retained constitutional limits and reservations, and impose conditions on EU law.
Moreover, constitutions are not only often considered to be expressions of the will of the people to form a polity (political autonomy) and to be governed under the constitution, but many constitutions also legally and judicially protect this foundational will.
This may take different forms, for instance by protecting the sovereignty of the state, statehood itself or the national nature of democracy, or a combination of these.

6. To put the constitutional obstacles to further EU integration in proper perspective, the report draws two main distinctions.
The first concerns a distinction between further integration under the current EU treaty framework and further integration by means of new (EU amendment) treaties.
The second distinction is that between substantive and procedural constitutional obstacles.
Generally, the substantive constitutional obstacles can be overcome by the adoption of a treaty (amendment), by the adoption of a constitutional amendment or by a combination of both.
For the adoption of such amendments, national procedural constitutional hurdles have to be taken.

7. Under the current EU treaty framework, substantive constitutional limitations to further EU integration by means of secondary EU law in many Member States relate to respect for national (constitutional) fundamental rights, respect for the limits of the powers transferred (EU acts must be intra vires, i.e. not exceed the competences of the Union, as interpreted under the constitution or the national acts approving the Treaties), and respect for the constitutional identity of the Member States (or their fundamental constitutional principles).
There is a great variety between the Member States: some have no or at least no specific or clearly articulated substantive obstacles for further integration under secondary EU law, while others are more explicit and develop all three categories of limitations.
Also the way in which these are shaped differs from one State to the next.

8. The procedural constitutional obstacles to further EU integration by means of secondary EU law regard participation requirements for the adoption of EU acts.
The existence of such requirements is provided for in EU law itself (e.g. ratification or approval in accordance with national constitutional requirements) or in Member States’ constitutional law (parliamentary scrutiny systems), or both.
The approval requirements themselves vary widely per country and range from approval, whether or not with a qualified majority, by resolution of the national parliament, approval by act of parliament or under the procedure for national constitutional amendment, and sometimes approval by act of parliament and referendum.

9. When it comes to further steps in European integration by way of amending EU Treaties, or concluding new Treaties, there is a broad variety among Member States as to the substantive obstacles which constitutions impose on further integration by treaties.
One set of obstacles is concerned with the sheer volume of powers transferred, which is then viewed to threaten fundamental principles of the constitution, such as statehood, national democracy or sovereignty. But usually, the substantive limits concern the values and principles that must be respected. Thus, several constitutions (are interpreted to) express the idea that the State can only ratify treaties and participate in the EU or international organisations in so far as these comply with the core values of the constitution. To varying degrees, they thus project their basic constitutional principles on the Union, and require the Union to comply with essentially the same principles.

10. With respect to procedural hurdles for further integration by way of amending EU Treaties or adopting new ones, it could be said that, as a general rule, the more a treaty impinges on a national constitution and the more it approaches its core values, or is considered to do so, the more difficult it becomes to ratify such a treaty, and the higher the procedural hurdles that need to be overcome.
These hurdles concern both the approval of the relevant treaty, and, should this be necessary, amendment of the constitution. Constitutional requirements on approval of EU Treaties vary from simple majority in parliament, to special majority for some EU Treaties, to special majority for all EU Treaties, to constitutional amendment by referendum (in Ireland).

11. If a Treaty submitted for approval is found to actually infringe the constitution, the procedural requirements become more stringent, and ratification will usually have to be preceded by a constitutional amendment. The procedural requirements for constitutional amendment vary to a large extent.

12. In some countries certain constitutional principles are considered so crucial that they are protected by constitutional provisions which are declared unamendable. If a proposed treaty reaches those constitutional limitations, approval can only be secured through other means and avenues.
This is especially the case in Germany, where an infringement of the German constitutional identity can only be overcome by the adoption of a new Constitution.

13. Against this background of national constitutional limitations, the avenues for further European integration can be found in two main strategies: (I) avoiding the existent substantive constitutional obstacles on the one hand, and (II) overcoming the obstacles, and making them disappear.

14. EU integration, both under the current treaty framework and beyond it, can be taken further while avoiding substantive constitutional obstacles. However, this has important implications for both Member State actors and EU institutions.
Under the current treaty framework, the most important manner to avoid constitutional blockages for the Member States actors is their abidance by the constitutional rules and principles. This requires that the Member States should not contribute to the making of EU law that would infringe their own Constitution, or, alternatively, they should negotiate exceptions.
For the EU institutions, it requires them to act in respect of national constitutional limits to integration.
Thus, the issue of the EU remaining intra vires requires the legislative, executive and judicial organs of the Union to take seriously the legal basis of EU action.
Strict abidance by the principle of subsidiarity can reduce the possibilities of running into constitutional obstacles for further integration.
In the context of fundamental rights protection, a mature and truly European system and culture of protection of fundamental rights is developing on the basis of the EU Charter and other mechanisms.
While this cannot fully replace national constitutional protection, and conflicts may continue to arise, especially due to differences in the balances struck between fundamental rights and other interests, and the different scope of certain rights, constitutional clashes can often be avoided.

Constitutional sensitivities specific to one or several Member States are sometimes addressed in EU legislation. This is not merely a matter of political sensitivity: there is also a broader obligation of the EU and its institutions under Article 4(2) TEU to respect the ‘national identities of the Member States inherent in their fundamental structures, political and constitutional, inclusive of regional and local self-government’, as well as ‘their essential State functions, including ensuring the territorial integrity of the State, maintaining law and order and safeguarding national security’.
This can be considered a recognition of the fact that the EU must pay due regard to the constitutional concerns of the Member States. At least as regards national obstacles that can be subsumed under Article 4(2) TEU, prudent decision-making is called for.

Generally, the EU institutions have several techniques at their disposal to avoid national constitutional obstacles and to accommodate constitutional diversity while engaging in further European integration within the present treaty framework. We mention the following:
* The choice of legal instrument (the choice for a directive might leave more leeway for implementation in accordance with national constitutional requirements);
* The use of techniques such as the ‘open method of coordination’ and other benchmarking techniques rather than harmonization;
* The use of minimum rather than total harmonization;
* The use of exemptions or differentiated regulation.

The practices listed above are premised on awareness and sensitivity in the EU institutions of national constitutional obstacles that further integration might run into. This in turn highlights the importance of an honest constitutional dialogue not only between courts, but also between European and national institutions.

15. By now, the state of EU integration has advanced so far, and the competences already transferred are so extensive, that almost every new transfer of competences in amending EU Treaties or new Treaties is likely to be constitutionally sensitive in at least one of the Member States. The spectrum of competences whose transfer is constitutionally problematic varies from Member State to Member State. But in its entirety the spectrum ranges from those competences which historically have formed the nucleus of national sovereignty and statehood (e.g. foreign affairs and defence, criminal law), via economic competences to competences related to national culture and the welfare state (social security etc.).
To a certain extent, national constitutional sensitivities regarding new transfers of competences which are particular to one or a few Member States can be accommodated, be it only at a certain cost.
One avenue for further EU integration respecting individual national constitutional sensitivities is to create treaty exemptions for those Member State who are not willing to integrate (further) in a certain area or field.
This is actually reflected in EU practice.
Various Protocols to the Treaties, from Maastricht to Lisbon, testify to this.
Another avenue for transferring new competences to the EU while respecting individual national constitutional sensitivities regards the way the competences are exercised at the EU level, which can guarantee that the Member State and its parliament remain in a position to exert a decisive influence on European decision-making procedures, i.e. unanimity.

16. Substantive constitutional obstacles, whether arising under or beyond the current treaty framework, can be overcome in different ways.
Some issues can be solved via an informal adaptation of the constitution.
More often, it will be necessary to adopt a treaty (amendment), a constitutional amendment, a combination of both or even a new constitution.
The prescribed route depends on the kind of constitutional obstacle encountered, but in all situations at least certain procedural constitutional hurdles have to be taken.
Even a (simplified) treaty amendment which does not encounter any substantive constitutional obstacle in the Member States needs to be approved by the national parliaments or in a referendum, or in both, depending on the requirements of national constitutional law.
If substantive constitutional obstacles are encountered, the procedural hurdles become higher. In nearly all such cases, qualified majorities in parliament are required, or a referendum, or again a combination of both. And in some Member States, proposals for further EU integration might even collide with obstacles deriving from provisions which claim to be unamendable.

These procedural constitutional obstacles should be put in perspective. The history of European integration shows that further integration has often led Member States to amend their Constitution. This has happened typically at times of Treaty amendments which entailed new steps in EU integration (think of, for instance, the Treaty of Maastricht), but also in cases of major steps in EU integration under the Treaties in force (such as in the case of the European arrest warrant).

Moreover, at least in some Member States the provisions which are claimed to be unamendable under the present national constitutional arrangement can themselves be amended. And even were this is not the case, the obstacle is not constitutionally insurmountable, as an entirely new constitution could be adopted.

16. While the procedural constitutional hurdles which need to be managed to overcome substantive constitutional obstacles are certainly not insurmountable, they should not be discounted too lightly.
Indeed, they may reflect deep-seated sensitivities which are also evident in the current political climate concerning European integration. The political context must not be ignored in assessing constitutional possibilities for even relatively small steps on the road to further integration.

17. This is a fortiori the case in the context of moving into a new constitutional order, for instance by giving the EU the power to decide on its own competences (the so-called Kompetenz-Kompetenz) or by giving up independent statehood under international law.
The perspective of a development towards a situation in which the scope of the constitutional orders of the Member States is formally no longer expression of political autonomy, and such orders no longer derive their powers from the national polity but top-down from the Union, poses challenges which may be – in a technical sense and from a strictly legal perspective – manageable, and can technically be framed in terms of constitutional law. However, at present they must be deemed to be politically unfeasible.
Here we are leaving the area of constitutional law and entering the realm of political speculation and assessment.
When engaging in further integration beyond the present Treaty framework, it is no longer merely a matter of constitutional sensitivity. Overall political and social realities are more decisive than constitutional rules.

1 Also known as the ‘precedence’, ‘priority’ or ‘supremacy’ of EU law; see the landmark decision Case 6/64 Costa v ENEL [1964] ECR 585.

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