Jan-Herman Reestman (University of Amsterdam)

Differentiated integration among EU member states may be the solution to the inability to unite all member states behind policies that some consider desirable or necessary to advance the European integration process, but it may also come at a price. In a way, the rocky history of the ratification of the Agreement on a Unified Patent Court tells the story in a nutshell. The Agreement is a treaty under international law to which only EU member states can be party, and which has been signed by 25 of them. At the time of writing, almost all conditions for its entry into force have been fulfilled: the final hurdle to be overcome is ratification by the German President. However, that will take some time, because first the German Constitutional Court will have to deal with complaints lodged against it. It is the second time that the German court reviews the treaty. The first time this resulted in the invalidation of the act by which the German Parliament approved the treaty: the Bundestag, the German lower house, had not adopted it by the required two-thirds majority. This time, that procedural condition has been met and substantive issues will take center stage. In other member states, the approval of the Agreement has not gone unnoticed too. It also had to be approved by qualified parliamentary majorities in several other member states because it transfers sovereign powers to an international organization. For the same reason, a referendum was necessary in Denmark. In Hungary, the Constitutional Court ruled the Agreement contrary to the Hungarian Constitution. It can therefore only be approved by the Hungarian Parliament and ratified by the Hungarian President after the adoption of a constitutional amendment. And should Ireland, which has signed the Agreement, ever want to ratify it, it has to amend its Constitution too, for which a referendum is required. In short, the road to the establishment of differentiated integration may be paved with all kinds of national constitutional obstacles, depending on the variety chosen and the states participating.

Differentiated integration inside and outside the EU legal order

Differentiated integration among member states comes in two varieties: inside the EU legal order, established by the Treaties themselves or on the basis of those Treaties by secondary EU law; and outside the EU legal order, via so called substitute EU Treaties. The enactment of secondary EU law which requires the consent of the Council and the conclusion of treaties are to a certain extent always conditioned by national constitutional law. Therefore, in order to determine whether and to what extent the establishment of differentiated integration complicates decision-making, a comparison must be made with the ‘ordinary’ or at least the ‘most obvious’ decision-making procedure for the relevant subject matter. That ‘ordinary’ or ‘most obvious’ decision-making procedure is decision-making by all member states inside the EU legal order if regulating the relevant subject matter is a competence of the EU, and the conclusion of an EU (Amendment) Treaty in case the EU lacks that competence.

There are only very few additional national constitutional obstacles to establishing differentiated integration inside the EU legal order. In fact, the only additional obstacle is that Ireland’s participation requires the consent of both houses of the Irish Parliament.

As regards differentiated integration outside the EU legal order, two categories of substitute EU treaties should be distinguished. The first consists of treaties which regulate subject matter which could also have been regulated in secondary EU law. The Schengen Treaties, the Prüm Convention, the Treaty on Stability, Coordination and Governance in the EMU, and the ESM Treaty, belong to this category. If we compare the national processes of treaty conclusion to the EU decision-making process, the additional national constitutional obstacles are manifold. They differ from one member state to another and may range from approval by parliament or by referendum, via constitutional amendments, to ratification. The second category consists of treaties which regulate subject matter for which no competence exists at the EU level. Instead of transferring the lacking competence to the EU by way of an EU (Amendment) Treaty, member states can opt for an ordinary treaty, as they did with the Agreement on the Single Resolution Fund. If we compare the national constitutional obstacles faced by ordinary treaties to similar obstacles faced by EU (Amendment) Treaties, no additional national constitutional obstacles have been detected. On the contrary, in some member states some substitute EU treaties have benefitted from the fact that they were not equated with EU (Amendment) Treaties: the national hurdles they had to clear were less high, given that they could be approved by a simple parliamentary majority, whereas the same subject matter wrapped in an EU (Amendment) Treaty would have required a qualified majority. But it should be clear that this minor advantage will never be decisive for the choice between a substitute EU treaty and an EU (Amendment) treaty. For that choice, the relinquishment of the requirement of unanimous ratification for substitute EU treaties is far more important.

No requirement of unanimous ratification

Substitute EU treaties have a huge advantage over EU (Amendment) Treaties: they do not require unanimous ratification. That means that a hitch somewhere along the line during the national treaty-conclusion phase will not necessarily frustrate the entire project. However, not all member states are equal in this respect. For some of the substitute EU treaties (the ESM Treaty, the Agreement on the Single Resolution Fund, and the Agreement on a Unified Patent Court) ratification by a core of large member states, among them France and Germany, was, or is, indispensable for their entry into force. It should be added that, although this was not necessary from a strictly legal perspective, it is questionable whether the Fiscal Compact would have entered into force if France and Germany, and perhaps Italy, had not accepted to be bound by it. That suggests in more general terms that the participation of these two or three member states is, from a political point of view, a conditio sine qua non of differentiated integration, at least if it takes place outside the EU legal order. But that of course is not a particularly surprising finding.