Croatia–Slovenia border

A bay with two names

When the two former Yugoslav republics became independent in 1991, they could not agree their border on land, and their sea boundary had never been drawn. The sharpest quarrel was over what Slovenia calls the Bay of Piran and Croatia the Bay of Savudrija/Piran: Slovenia claimed all of it, and Croatia wanted a median line.^[1][2][3]

After years of failed talks, on 4 November 2009 the two countries signed an arbitration agreement, with the European Commission’s help. The tribunal was to decide the land and sea boundary, Slovenia’s “junction” to the high sea, and how the waters would be used.^[2]

The 2017 award

In July 2015 recordings leaked of telephone calls between the Slovenian judge on the tribunal and Slovenia’s official representative to it. Croatia withdrew, saying the process had been compromised, and has said it does not consider the proceedings binding.^[3][1]

The tribunal carried on and gave its final award on 29 June 2017. On land it fixed the line in more than twenty disputed areas, mostly following cadastral boundaries set by the Austrian Empire in the 1800s for tax purposes. It gave the larger part of the bay to Slovenia, adjusted the equidistance line at sea in Slovenia’s favour because of Cape Savudrija, and created a “junction area” through Croatia’s territorial sea where ships and aircraft heading to and from Slovenia have freedom of communication.^[1][2]

“the equidistance line must be adjusted in favour of Slovenia”^[1]

Stalemate

Slovenia says the award is final and binding and is implementing it on its side. In July 2018 it took Croatia to the EU Court of Justice, arguing that refusing the award broke EU law, and complaining that Croatian police escorted fishing boats in the contested waters.^[2][3]

On 31 January 2020 the court ruled that it had no jurisdiction. Croatia’s prime minister, Andrej Plenković, called it a victory for Croatian arguments and again proposed bilateral talks; Slovenia’s foreign minister, Miro Cerar, said the ruling still made clear that both states must comply with the award.^[3]

Both countries are in the EU’s Schengen area. Slovenia reintroduced checks on its border with Croatia on 21 October 2023, citing an increased terrorist threat, and lifted them on 11 June 2026.^[4]