There is a curious dispute between Croatia and Slovenia in regards to their land and maritime border. It appears to be ongoing since the breakup of Yugoslavia.

Noticeably Slovenia tried blocking Croatia’s bid to join the EU up until 2013, when it appears they stopped trying?

From there on it appears that everyone was okay, even Slovenia, with Croatia joining and staying in the EU even though the issue was never resolved.

In short, other factors, more valuable than the border dispute, must have motivated, or pressured, Slovenia to give up vetoing Croatian membership.

What could have possibly been more important to the Slovenians or its leaders?

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    Have you read this Wikipedia article? en.wikipedia.org/wiki/Croatia–Slovenia_border_disputes
    – Don Hosek
    Mar 20, 2021 at 3:41
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    There are quite a lot of bits of historical baggage in the EU. Spain claims Gibraltar and the Republic of Ireland had a claim on Northern Ireland in its constitution for many years. Also Poland is still claiming hundreds of millions of Euros from Germany in reparations for WWII, and Greece would like the Elgin Marbles back. As long as nobody starts threatening violence this is all fine as far as the EU is concerned. Mar 20, 2021 at 15:49

2 Answers 2


The rule regarding EU accession and unsettled border disputes is simply that the EU does not want to get dragged into ongoing border conflicts by new members. It is not an absolute, automatic bar to EU membership. There is also an "ongoing" border dispute between Germany and the Netherlands. But things are sufficiently amicable that both are EU members in good standing.

  • How would judicial jurisdiction work for the disputed territory? Would the courts for both countries or neither countries be recognized?
    – M. Y. Zuo
    Mar 20, 2021 at 16:46
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    @MichaelZ, cases like this in Europe tend to be about river bottoms, mountain tops, or tidal mudflats.
    – o.m.
    Mar 20, 2021 at 18:53
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    And what does that imply for jurisdiction?
    – M. Y. Zuo
    Mar 20, 2021 at 22:49
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    @MichaelZ, for things like barge traffic or fishing there are treaties. And I'm not aware of any murders on ships in disputed rivers.
    – o.m.
    Mar 21, 2021 at 6:58
  • What jurisdiction do these treaties assign as the predominant one? Or is it a condominium?
    – M. Y. Zuo
    Mar 21, 2021 at 16:49

I've noticed a significant level of misunderstanding about this issue. At that particular point, resolving border disputes or bilateral issues shouldn't have been a precondition for EU membership. Otherwise, Cyprus would've never joined the club. Slovenia became an EU member state while having the same dispute with Croatia.

What changed in 2004 is that Slovenia's position became incomparably stronger (due to the accomplished EU membership) to the level of blackmailing and political extortion towards Croatia. What no one elaborates is that Slovenia's territorial aspirations were extremely irrational and completely out of proportion. For that reason, Slovenia had always avoided going to court.

What changed dramatically in 2005 is that Slovenia unilaterally annexed 234 sq km of the Croatian territorial sea in NW Istria (an increase of 130% compared to what they had presented in their documents when joining the EU) and additional 350 sq km of self-proclaimed so-called Exclusive Economic Zone, far away from Slovenia's coastal strip - categorically demanding Croatia's recognition of its territorial appropriations. This extortion attempt (which Slovenia had to legally nullify a decade later, in 2018) delayed the Croatian accession talks for about a year.

Territorial Appropriation by Slovenia in 2005

The Slovenes had to approve the solution of the territorial dispute by the ad hoc Arbitration in a national referendum in 2010. They did that narrowly by 51.5% which enabled Croatia to move on. But the Arbitration was entirely tailored in favour of Slovenia's aspirations. Later, they didn't play by the book and messed up seriously which allowed Croatia to reject the Arbitration altogether and join the EU practically "without" Slovenia's consent.

Ironically though, in the meantime, the so-called "High Seas" (the main Slovenian excuse for territorial demands) simply vanished in the Adriatic (due to EEZ jurisdiction extensions) making Slovenia's demands and wishes even more redundant and absurd.

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