For a country to join the European Union is a long and difficult process. The new member state must meet requirements and be approved by existing member states.

What process applies if an existing member state expands its territory? For example, in the German reunification, East Germany joined West Germany. In a hypothetical future scenario, the Republic of Ireland might unify with Northern Ireland re-joining the EU. More contentiously, a hypothetical unification of Romania and Moldova would imply that the territory now controlled by Moldova joins the EU, even though Moldova is still far from meeting the accession criteria and, as of August 2022, negotiations have not yet started.

Suppose that — for example — Romania and Moldova would mutually agree to unify, and organise this such that Moldova accedes to Romania. Normally, if two countries mutually agree to unify under their correct democratic process, other countries would recognise this unification. Does this mean that the EU would "automatically" expand, or can the EU block such a process based on the consideration that the new area is not up to EU standards?

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    It was a complicated law matter even at the time of German reunification: ejil.org/pdfs/2/1/2023.pdf Mar 27, 2019 at 10:54
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    Basically if there's a (political will) there's a way: "But in the end, amazingly, everything worked out. The main reason was that once we were in an accelerated rhythm, member states didn't want to make difficulties and the European Parliament was fully collaborative." euractiv.com/section/future-eu/interview/… Mar 27, 2019 at 11:03
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    It’s possible for territory of a member state not to be part of the EU, e.g. the Faroe Islands: Special member state territories and the European Union. However, their status is based on an agreement between the parties concerned. I’m not sure what would happen if a country grew without an agreement or against other member states’ wishes.
    – chirlu
    Mar 27, 2019 at 11:04
  • @chirlu: I kinda doubt they'd do that in the cases cited, because it's in the Treaty itself that those have "remoteness, insularity, small size"... Mar 27, 2019 at 11:23
  • Closely related: politics.stackexchange.com/q/24616/130
    – gerrit
    Dec 7, 2021 at 20:03

2 Answers 2


There are a lot of elephants in the room. And these are individual treaties of accession of the countries in question. Foreseeing possible such expansions, they sometimes have special provisions. Some examples, from a 2017 article:

Taoiseach Enda Kenny has asked recently for a special provision in any Brexit deal to allow Northern Ireland to rejoin the EU should it be united with the Republic. He did so, notwithstanding the fact that a special deal for Northern Ireland is the declared goal of the UK government.

So, the question is how could such a provision look like?

Obviously, there are not many EU law provisions that regulate the (re)unification of (Member-)States. The closest example is Article 4 of Protocol No 10 on Cyprus of the Act of Accession 2003. Protocol No 10 provides the terms for the application of EU law in Cyprus given that the island had not been unified at the moment it joined the EU. In particular, it provides for the suspension of the application of the acquis in northern Cyprus, a suspension which shall be lifted in the event of a solution.

If such solution occurs in the future, Article 4 provides for a simplified procedure that enables the Union to accommodate the terms of the reunification plan. In particular, Article 4 allows the EU, by a unanimous Council Decision at a future date and in the event of reunification, to alter the terms of Cyprus’ EU accession that are contained in the Act of Accession 2003. In other words, it allows the Council to amend primary law (ie the Act of Accession 2003) with a unanimous decision.

This might sound like a heresy. However, the Treaties foresee special procedures for their amendment in some cases. The best example, for the purposes of this post, is the Council decision on the basis of Article 2(2) of the 1994 Accession Treaty which adjusted the instruments of accession after Norway’s failure to ratify. Several Articles of this Accession Treaty and of the Act of Accession were amended by a Council decision while other provisions were declared to have lapsed. Thus, in that case, the Council, itself, amended primary law in a simplified procedure without any ratification of the Member States.

To the extent that the ‘Brexit’ Agreement will be considered as part of primary law, a similar provision regulating the reunification of Ireland could be included and could assist the smooth transitioning of Northern Ireland back to the EU. Of course, the question of the reunification of Ireland –as many other questions related to Brexit- is first and foremost political. It is important to point out, however, that EU law is flexible enough to accommodate such political developments.

So at least one reunification/expansion (that of Cyprus) is basically pre-ratified; well, there's an accelerated procedure for it already in place, probably inspired from the German precedent, in which the procedure was more ad-hoc, but it mostly involved the Council. The Cyprus case isn't terribly controversial though, because few countries recognise the Turkish/Northern Cyprus.


It's not really a question of what the EU would do, it's a question of what the country expanding decides to do. If the new territory that is joining an existing member state it will adopt all laws, governance and international treaties of that member state. Since the EU is, at its core, a stack of international treaties it would automatically become a member.

The EU is somewhat unprepared for this eventuality, which as you point out would bypass the usual entry requirements. However, as you also point out it's not the first time it's happened, i.e. with East Germany, and it's not an insurmountable problem.

The EU would then be responsible for ensuring compliance with EU rules, so for example the customs union and all standards. The EU also provides assistance to member states to help them develop, so significant funding would likely be made available.

The EU could also ask the existing member state to help, e.g. by moving its existing border controls and using its existing systems to quickly establish a new frontier.

  • One has to wonder if they haven't added any provisions (on such expansions) to subsequent EU treaties since the German reunification... Mar 27, 2019 at 14:44
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    @Fizz you don't have to wonder, you can simply check as the treaties are all published. There simply isn't much point expecting all that political will and effort on something that is fairly rare and probably better handled on a case-by-case basis anyway.
    – user
    Mar 27, 2019 at 15:48

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