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The period 1992–2002

The year 1992 saw the creation of an expert working group for the border issue. Between 1993 and 1994, 53 cadastral discrepancies of more than 50 metres were identified on land, which served as the basis for further work.


The Mixed Diplomatic Commission for the Establishment and Demarcation of the Slovenian-Croatian Border and the Final Agreement on the Border, which operated from 1993 to 1998, proposed solutions for the land boundary, except in four areas, namely Prekmurje, Sekuliči, Tomšič plot-Snežnik and Dragonja, but found no solution for the maritime delimitation. 


Then in 1999, the parties chose a mediator, namely former US Defence Minister William Perry. The mediation didn't lead to a result.


Thus in 2001, bilateral talks resumed, first within the Mixed Diplomatic Commission and then at the Prime Ministers level via a special negotiating delegation. This resulted in the  Treaty on the Common State Border (54 KB), initialled on 20 July 2001 and commonly referred to as the Drnovšek-Račan Agreement. The treaty had been confirmed by both governments on 19 July 2001


The Slovenian Government confirmed the initiative for the conclusion of the Račan-Drnovšek Agreement the same day as the Slovenian National Assembly Committee on Foreign Policy, namely 19 July 2001. Prime Minister, Dr. Janez Drnovšek, was authorized to sign the treaty. This concluded the bilateral border negotiations. However, in September 2002, the Croatian side informed the Slovenian side in a letter that Croatia cannot accept the initialled treaty.



The period 2002–2008

Following a number of incidents on the border, on 10 June 2005 in Brijuni, the Slovenian and Croatian governments signed the  Joint Declaration on Avoidance of Incidents (73 KB). Its purpose was not to resolve the border dispute, but to ensure adherence to the status quo as at 25 June 1991 in order to avoid further incidents. 


In July 2007, Slovenia proposed resolving the dispute through the conciliation procedure before the OSCE Court of Conciliation and Arbitration, which Croatia refused. 


In early August 2007, Croatia proposed that the dispute be submitted to the International Tribunal for the Law of the Sea (ITLOS). Slovenia found this proposal unacceptable since it was important for Slovenia that the final border solution included both land border and maritime boundary.


Following this exchange concerning the possibility of a third-party mediation, on 27 August 2007, Prime Ministers of Slovenia and Croatia Janez Janša and Ivo Sanader reached a informal agreement in principle, known as  the Bled Agreement (469 KB), envisaging that the dispute be referred to a judicial body. This led to the appointment of a Slovenian-Croatian team of legal experts tasked with drafting the required draft special agreement. 


In April 2008, the Slovenian Government and the National Assembly Committee on Foreign Policy passed  the negotiating positions (54 KB) regarding the  Special Agreement between Slovenia and Croatia on the Submission of the Border Dispute to the International Court of Justice or to Arbitration. (370 KB) In September 2008, Croatia put forward its own  draft Special Agreement (124 KB) and proposed further negotiations. The mixed group of legal experts met four times, finally on 28 January 2009. However, no agreement was reached, and consequently, the Slovenian side of the group ceased working. 



The period 2008 - 2009

In the autumn of 2008, the Slovenian Government temporarily suspended Croatia's EU accession negotiations because Croatia in several negotiating chapters prejudged the final course of the border. In December 2008, the Slovenian Government, with French mediation, attempted to have the elements prejudging the course of the border eliminated, but failed to obtain firm assurances from the Croatian side. 


January 2009 saw the beginning of the Rehn Process, which was initiated by the then EU Commissioner for Enlargement, Olli Rehn. The process concluded on 18 June 2009 with Croatia's decision to withdraw from further talks.  


Commissioner Rehn was of the opinion that the border dispute and the standstill in Croatia's accession negotiations should be resolved concurrently. He first proposed mediation, which Croatia refused.


Then in March 2009, he proposed arbitration, to which Slovenia agreed in principle, insisting on 25 June 1991 as the critical date and on the application of the principle of equity, including respect for vital interests and other relevant circumstances. However, Croatia rejected this proposal as well and insisted that the dispute be referred to the International Court of Justice.


On 22 April 2009, Commissioner Rehn put forward a draft agreement on the dispute settlement, which is known as Rehn's first proposal. This time, Croatia agreed to what was proposed, but Slovenia suggested some amendments.


Rehn's second proposal, which took into account the Slovenian amendments, was presented on 15 June 2009. However, Croatia, opposing such changes, withdrew from further talks on 18 June 2009 in Brussels. 


On 31 July 2009, Slovenian and Croatian Prime Ministers Borut Pahor and Jadranka Kosor met at Trakošćan Castle and agreed to resume talks on the basis of the following three principles:


  • the elimination of the elements prejudging the course of the border on the part of Croatia;
  • Slovenian consent to the continuation of Croatia's EU accession negotiations, which were suspended due to Croatia prejudging the border; and
  • the agreement on the dispute resolution. 


After the meeting in Ljubljana on 11 September 2009, the Croatian Prime Minister sent a written statement to the Swedish Presidency of the Council of the EU, declaring that no document, position, law, map or any other unilateral act or measure adopted after 25 June 1991 would prejudge the final solution of the border dispute. As a result, at the following Intergovernmental Accession Conference in October 2009, Slovenia withdrew its reservations to the negotiations chapters where the cause for such reservations ensuing from Croatia's prejudging the border. In addition, it was agreed that the negotiations on the border dispute would continue on the basis of Rehn's second proposal.

Conclusion of the Arbitration Agreement

 The Arbitration Agreement between the Government of the Republic of Slovenia and the Government of the Republic of Croatia (1.7 MB) was signed in Stockholm on 4 November 2009 by the Prime Ministers of both countries and the Swedish prime minister as a witness on behalf of the EU Council Presidency. 



The period 2010– June 2017


The Arbitration Agreement entered into force on 29 November 2010. On 25 May 2011, it was registered with the UN Secretariat by both countries, in accordance with Article 102 of the UN Charter.


In the Agreement, Slovenia and Croatia agreed to refer the open border issue to an arbitral tribunal. They also agreed that, unless envisaged otherwise in the Arbitration Agreement, the Arbitral Tribunal would conduct proceedings according to the  Permanent Court of Arbitration Optional Rules for Arbitrating Disputes between Two States (148 KB), and that it would be supported by a secretariat ensured by the Permanent Court of Arbitration in The Hague.



11 February 2013 marked the beginning of the written round of the proceedings, with the submission of Memorials, in which each side presented its views regarding the course of the border. The submitted documents are not publicly available, because the proceedings are confidential, in accordance with Article 6/5 of the Arbitration Agreement. The Slovenian Memorial is over 650 pages long and includes around 5,200 pages of annexes and 250 pages of maps, while the Croatian one totals some 3,600 pages.


The exchange of Memorials marked the beginning of the second round: the drafting of Counter-memorials, in which each side responded to the other side's positions. 


The counter-memorials were submitted on 11 November 2013.



The rules of the Permanent Court of Arbitration allow the possibility of a third written round, with the parties submitting Replies to Counter-memorials. Thus, at Slovenia's proposal, the Arbitral Tribunal allowed further responses to further clarify facts and newly-submitted documents. On 26 March 2014, the parties exchanged Replies to the Counter-memorials. 


The oral hearings were held at Hague's Peace Palace in The Hague, the headquarters of the Permanent Court of Arbitration, from 2 to 13 June 2014. 


The countries' positions were summarised in a press release issued by the Permanent Court of Arbitration on 17 June 2014 .



22 July 2015: the Serbian and Croatian newspapers Kurir and Večernji list report about alleged phone conversations between the Slovenian agent Simona Drenik and arbitrator Jernej Sekolec, and proceed by publishing audio recordings of the alleged conversations.  


23 July 2015: the Permanent Court of Arbitration announces that the arbitrator, Jernej Sekolec, has resigned and invites Slovenia to appoint a new arbitrator  in accordance with the Arbitration Agreement. 


24 July 2015: Croatia writes to the Arbitral Tribunal  and requests that the proceedings be suspended in the light of the tapped phone conversations. 


26 July 2015: Slovenia responds to the Court's call  and announces that it will appoint a new arbitrator in 15 days. It also expresses regret over the events reported by the Croatian media.  


27 July 2015: Slovenian Prime Minister Dr. Miro Cerar addresses a letter to Croatian Prime Minister Zoran Milanović, insisting that only the arbitration proceedings will yield a just solution to the border dispute and that the proceedings are the foundation for the continued good neighbourly relations. The same day, Slovenia informs the Tribunal of its disagreement with the possible suspension of the proceedings.  


28 July 2015: the Slovenian Government appoints Ronny Abraham, a French lawyer and the ICJ President, as its new arbitrator. The same day, it is announced that the Tribunal will decide on Croatia's claim of 24 July and hear the parties on this question.  


29 July 2015: the European Commission expresses full support for the arbitration proceedings  and announces that they will continue even if Croatia decides to unilaterally terminate the Arbitration Agreement. It also urges Croatia to continue the proceedings. 


30 July 2015: the Croatian Foreign Ministry sends a note to the Slovenian Foreign Ministry , communicating that all conditions required for the termination of the Arbitration Agreement have been fulfilled. The same day, Croatia's arbitrator, Budislav Vukas, resigns. 


31 July 2015: Croatia notifies the Tribunal in writing  of its intention to terminate the Arbitration Agreement. The Croatian Prime Minister informs his Slovenian counterpart of Croatia's intention to terminate the Arbitration Agreement. The same day, Slovenian Prime Minister Dr. Miro Cerar replies that the Arbitration Agreement is the only applicable legal basis for the resolution of the border dispute  between the two states and expresses the expectation that the Arbitral Tribunal will promptly decide on the further arbitration proceedings.


5 August 2015: the Slovenian Foreign Ministry rejects Croatia's notification of termination sent via diplomatic channels. The Permanent Court of Arbitration announces that Judge Ronny Abraham has resigned as arbitrator. 


13 August 2015: Slovenia requests the President of the Arbitral Tribunal to appoint a new arbitrator.  

In a separate letter, Slovenia also responds to Croatia's letter and objects to its intention to unilaterally terminate the Arbitration Agreement.  According to the Slovenian side, the Tribunal has the power and duty to continue the proceedings. Slovenia also stresses that Croatia has fulfilled its vital interest by joining the EU in accordance with Article 9 of the Arbitration Agreement, which it now wishes to terminate. According to the Slovenian side, each tribunal has the power to determine the scope of its own competence, which is the general principle of international law governing arbitration proceedings. 


14 August 2015: following Slovenia's decision to leave the appointment of a new arbitrator to the President of the Arbitral Tribunal, the European Commission reiterates its full support for the arbitration proceedings.


19 August 2015: the Permanent Court of Arbitration announces that once re-constituted, the Tribunal will consider the parties’ positions carefully , including in respect of the effect of Croatia's stated intention to terminate the Arbitration Agreement and in respect of the possible implications for the present proceedings of the events reportedly underlying Croatia's decision. 


25 September 2015: the President of the Arbitral Tribunal appoints new arbitrators : Ambassador Rolf Fife (Norway) and Professor Nicolas Michel (Switzerland).


30 September 2015: European Commission President Jean-Claude Juncker and First Vice-President Frans Timmermans address a joint letter to Prime Ministers Dr. Miro Cerar and Zoran Milanović, welcoming the re-constitution of the Arbitral Tribunal and urging both sides to respect the Tribunal's decisions. In addition, they emphasise that border disputes among EU Member States should be resolved promptly, as they can have an impact on the application of EU law. 


9 October 2015: Slovenian Prime Minister Dr. Miro Cerar replies to the joint letter  by the European Commission's President Juncker and First Vice-President Timmermans. He stresses that the arbitration proceedings are based on the Arbitration Agreement, in the conclusion of which the European Commission played an active role. The Agreement was signed in the presence of the Presidency of the EU Council and was a condition for Slovenia's withdrawal of its reservations concerning Croatia’s EU accession.


2 December 2015: the arbitration tribunal announces that it will decide on questions arising from the letters sent by Slovenia and Croatia in July and August 2015  and invites the parties to make further submissions: Croatia by 15 January 2016 and Slovenia by 26 February 2016. In addition, it schedules a hearing in March 2016.



14 January 2016: Croatia announces through the media  that it will not respond to the Arbitral Tribunal.


26 February 2016: Slovenia files its written submission; in accordance with Article 6, paragraph 5, of the Arbitration Agreement, the content is confidential. 


3 March 2016: on the proposal of Slovenian Agent Mirjam Škrk and the Foreign Ministry, the Slovenian Government appoints Nataša Šebenik as Co-Agent in the arbitration proceedings. 


17 March 2016: Slovenia presents its positions at a hearing held at the Permanent Court of Arbitration. Summary of positions of both parties 


30 June 2016: The Arbitration Tribunal announces "Arbitration between Croatia and Slovenia to continue ". The Tribunal's partial award  is available at the Permanent Court of Arbitration website.

19 June 2017: The arbitration tribunal has announced it will render its final award on the course of sea and land border between Slovenia and Croatia on 29 June .



The period June 2017 - December 2017

29 June 2017 The Arbitral Tribunal in The Hague pronounces its final ruling in the arbitration between the Republic of Slovenia and Republic of Croatia  concerning the demarcation of the border on land and sea between the two countries. Croatia responded to this by declaring that the arbitration ruling did not exist for them.

The arbitration ruling was based on the Arbitration Agreement, which is a binding treaty valid in international law. Through its non-recognition of the ruling, Croatia added the Arbitration Agreement to the list of numerous bilateral agreements with Slovenia that Croatia signed but later failed to observe or implement, or observed only in part in so far as it was in the Croatian interest:
- agreement on joint defence in the event of aggression by the Yugoslav military (1991)
- border agreement initialled by Drnovšek and Račan (2002)
- agreement on the Krško nuclear power plant (2003)
- memorandum on foreign currency savers (Mokrice, 2014).

4 July 2017 First
Vice-President of the European Commission Frans Timmermans  expressed on behalf of the Commission the expectation that Slovenia and Croatia would implement the arbitration ruling.

12 July 2017 on the initiative of Slovenia, a meeting was held in Ljubljana between
Slovenian Prime Minister Cerar and Croatian Prime Minister Plenković. 

4 September 2017 on the sidelines of the Bled Strategic Forum, Prime Minister Cerar and First Vice-President of the European Commission Timmermans discussed European topics and arbitration with Croatia

19 December 2017 on the initiative of Croatia
the prime ministers of the two countries met in Zagreb . This did not bring their positions any closer, since Croatia persists in its non-recognition of the arbitration ruling.

29 December 2017 – expiry of the six-month instructional period to prepare for implementation of the arbitration ruling.