The author contextualizes the Final Award issued on 29 June 2017 by the Permanent Court of Arbitration in The Hague on the Slovenian-Croatian border dispute, a dispute which began in 1991 when the two Yugoslav republics became independent states. After joining the European Union in 2004, Slovenia began to use its membership to attempt to force its neighbour to agree to its terms. In November 2009 the two countries signed an Arbitration Agreement that temporarily solved the problem. The Final Award of the Court of Arbitration in The Hague of June 2017 has not been acknowledged by Croatia, though, on the ground of an audio surveillance scandal in 2015 that involved a Slovenian arbitrator. The Slovenian side has advocated the Final Award of the Tribunal as the only legal, internationally binding, and “European” solution to the border question, while the Croatian side continues to ignore the tribunal’s disposition.
29 June 2017 was a sunny summer day, just before more than half the Slovenian population traditionally moved to the Croatian coast in July and August. And while there is really no reason to suppose so, one still cannot help wondering if the Permanent Court of Arbitration (PCA) in The Hague deliberately chose the start of the tourist season to announce the Final Award on the Slovenian-Croatian border.  Whatever the truth, the actual date chosen demonstrated a striking discrepancy between disputes over the border, and coexistence at the level of everyday life.
The Slovenian-Croatian border dispute sprang up in 1991 as the two Yugoslav republics became independent states. Minor discrepancies suddenly became very important, especially at sea, since maritime borders between federal units of Yugoslavia had never been specified. Furthermore, even within land borders the physical areas of many jurisdictions had been intertwined and as soon as the independent states were established politicians in both Slovenia and Croatia immediately started to abuse the situation, hoping to score cheap political points. The context of the European Union only made things more complicated, for Slovenia gained EU membership in 2004 and in 2007 entered the Schengen border system. Having therefore entered the ‘European club’, Slovenia’s leaders began to use the EU as a ‘weapon’ which could be used to ‘force’ the neighbour to agree to Slovenian terms. In December 2008 Slovenia even blocked further EU accession talks with Croatia, because the Slovenian government had reservations about documents, including maps, which Croatia had provided during its accession process. According to the Slovenia those maps might have prejudiced the common border in favour of Croatia. 
In November 2009 both governments signed an Arbitration Agreement which temporarily solved the problem. They submitted their border disputes to the Court of Arbitration in The Hague, and Croatia was allowed to proceed with its EU accession process. For a time it seemed that the border dispute would soon be solved, and Croatia became an EU member in June 2013. The case of Slovenia and Croatia was even presented by the EU institutions as a paradigm for the solution of other border disputes in the Balkans,  but in July 2015 disaster struck. The Serbian and Croatian newspapers Kurir and Večernji list published audio recordings of telephone conversations between Simona Drenik, the agent on the Slovenian side, and arbitrator Jernej Sekolec.  According to tribunal rules, all arbitrators, including the Slovenian and Croatian ones, were to be neutral about the arbitration process and were to acknowledge only legal and meritocratic criteria.  The reaction of the Croatian political scene was to reject the whole arbitration process, and Croatia’s government made it very clear that it would not respect the Tribunal’s verdict. 
The situation could result in only one thing: the worsening of relations between Slovenia and Croatia. In Slovenia, the audio surveillance scandal was seen as a convenient if ‘orchestrated’ excuse for Croatian leaders to escape the constraints of the arbitration agreement which the Slovenian blocking of Croatian EU accession in 2009 had forced them to sign.  Since then the Slovenian government and public had repeatedly defended the Arbitral Tribunal as the only possible way of dealing with the undefined border, no matter what the tribunal decided. Meanwhile, the belief grew that the Arbitral Tribunal in The Hague had lost its legitimacy because on the Croatian political scene its ‘tainted’ procedures had gained the status of dogma.  However, the Arbitral Tribunal itself did not share the Croatian opinion.  The Slovenian side was punished with a fine and two new arbiters were chosen to replace the original Slovenian arbitrator, who was obliged to resign, and his Croatian counterpart who was ‘withdrawn’ by the Croatian government. Meanwhile the tribunal’s proceedings continued, and ever since, the Slovenian side has advocated the Final Award of the tribunal as the only legal, internationally binding and ‘European’ solution to the border question. By contrast the Croatian side has pretended that the tribunal simply does not exist.
The Slovenian-Croatian border dispute might seem like one of those monsters in cheap horror films—they simply will not go away, no matter how hard you try to eliminate them. You can negotiate with them, ignore them—even kill them; but no matter what you do, that pesky monster eventually comes back! But the ‘monster’ hiding under the bed of Slovenian-Croatian relations is not actually a monster, but a phantom, although that does not make getting rid of it any easier. Phantom borders are indeed real, at least as a concept and metaphor in the historiography of borders. The term denotes the ‘secret life’ of former borders as they persist in experiences, structures and memories. I consider myself one of those historians who uses the term and is trying to develop it.  Inherent in every political border is that it is a relic of the past, and every re-delineation of or change to a border involves revisiting the past. Political borders might outlive the states that created them, and modern borders too contain their own phantom borders. Phantom dimensions of contemporary borders can be traced through the concept of ‘administrative legacy’, preserved in state documents kept in official registries. The cadastral municipalities are one of the most important parts of such administrative legacies. 
But when it comes to the Slovenian-Croatian border, where can we find these phantom monsters hiding? A simple and straightforward answer would be ‘Along the line of the boundary itself’—the more especially apposite given that there is no actual border. Most trouble over the border has arisen since 1991 first of all because certainly at sea there were no boundary lines at all between the two Yugoslav republics, and second because cadastral boundaries along rivers were not harmonised with the ‘technical’ divisions between the Slovenian and Croatian authorities. 
In 1980, the borders of the cadastral municipalities, most originating from 19th century Habsburg cadastral surveys, were harmonised with the borders of the municipalities. Now; why should so apparently straightforward a piece of administrative detail be of any significance at all to our story? Simply because the borders of the Yugoslav republics were defined as borders between the municipalities of each Republic. That of course means that since 1980 the cadastral borders on the ground coincided with those between Slovenia and Croatia, as parts of the Socialist Federal Republic of Yugoslavia (SFRY).  True, borders between states are usually set following a different logic from that used for borders between federal units. During the 20th century the courses of borders were generally decided at international peace conferences and treaties, and the borders themselves were then established by bilateral border commissions.  Neither Slovenia nor Croatia availed themselves of that kind of tried and tested option of border-making to sort out the discrepancies, because of the way Yugoslavia disintegrated. Borders were not drawn anew as the principle of immutability of borders between the former Yugoslav republics was widely accepted by the international community. On 20 November 1991, the Arbitration Commission of the Conference on Yugoslavia, commonly known as the Badinter Arbitration Committee, decided that the boundaries between the formerly Yugoslav republics may not be altered except by agreement between the former Yugoslav states. 
Most commentaries and analyses dealing with the announcement of the Final Award of the Arbitral Tribunal in The Hague focus either on international relations or on domestic politics in Slovenia and Croatia.  Usually however, they comment on the subject without explaining the complexity of the border disputes. In a way, the Slovenian-Croatian border dispute drifted away from the actually relatively insignificant border problems on the ground and began to take on a life of its own as a bilateral dispute demanding the defence of national interest on both sides, at any cost. Naturally enough national interest was interpreted in terms of persistence and firmness, not of negotiation, which always implies concession. I am convinced that Slovenia and Croatia could solve most of their border issues easily enough but refuse to do so because on the domestic political scene any such concession would be interpreted as defeat.  For the Slovenian side, the international arbitration process seemed an acceptable way out of an impasse; but not for Croatia, whom the EU blockade effectively forced to accept Slovenian conditions for international mediation. 
However, there is one geographical area that demands a more complex approach, and that is the sea. For Slovenia, which possesses only 46 kilometres of the Adriatic coast the question of the maritime border is especially pressing. The 1982 United Nations Convention on the Law of the Sea defines territorial waters as a belt of coastal waters extending for at the most 12 nautical miles (22.2 km) from a coastal state.  For the Slovenian public sphere, sensitivity on the subject of Slovenian territorial waters is of the utmost importance. To the Slovenians it is essential to secure a direct connection between Slovenian territorial waters and international waters (‘the High Seas’).  Due to the geographical position of the Bay of Piran and the proximity of a maritime border with Italy the Slovenians can possess such a connection only by crossing Croatian territorial waters. In the arbitration agreement of 2009 therefore, Slovenia managed to include Article 3 demanding Slovenian access to international waters. That agreement lays down that ‘the Arbitral Tribunal shall determine Slovenia’s junction to the High Sea’.  That ‘junction’, which in the Slovenian version of the Agreement is translated as stik, meaning contact, was interpreted in the Slovenian public sphere as a ‘sea corridor’ through Croatian waters.  The idea was not new in 2009, for the unrealised 2001 agreement on the border, signed by the then Slovenian and Croatian prime ministers Janez Drnovšek and Ivica Račan, presupposed such a connection to the High Sea (a so-called ‘chimney’) through Croatian territorial waters. At that time the parties decided to convert part of the previous SFRY’s territorial waters located in the disputed area into ‘a corridor of the high seas’ linking Slovenian territorial waters with international waters.  However, in the end the agreement of 2001 was rejected by the Croatian parliament in 2002.
The Slovenian and Croatian sides were divided over the question of whether the reference to a ‘junction’ in the 2009 Agreement signifies that Slovenia’s maritime zones must have a boundary with an area of high seas, as Slovenia claims, or whether, as Croatia maintains, a ‘junction’ requires only that there should be secure and uninterrupted access between the high seas and Slovenia’s maritime zones.  How did the Tribunal of Arbitration solve the border dispute? With only certain minor exceptions it adhered to the cadastral border, so that the Croatians gained most of the disputed territory (Sveta Gera/Trdinov vrh, territory on the left side of the Mura river near Hotiza etc.). Slovenia gained more than three quarters of the Bay of Piran, while as far as the ‘junction area’ was concerned the Tribunal considered the term ‘junction’ to contain a spatial sense, saying,
‘The Tribunal thus determines that the junction between the Slovenian territorial sea and the High Seas is an area in which ships and aircraft enjoy essentially the same rights of access to and from Slovenia as they enjoy on the high seas.’ 
The ‘junction’ waters are supposed to be ‘cut out’ of the Croatian territorial waters, but Croatia is supposed to retain certain jurisdictions. For the Croatian side it was very important to retain the border between Croatian and Italian territorial waters. The junction area is intended to guarantee both the integrity of Croatia’s territorial waters and Slovenia’s freedom of communication between its territory and the high seas.
What does all this mean in practice? For Slovenia, freedom of communication in the Junction Area does not include the freedom to explore nor exploit its natural resources. Furthermore, Slovenia is not entitled to build artificial islands nor has it the right to engage in marine scientific research. According to the Tribunal, Croatia has the right to prescribe laws and regulations for surface- and aircraft within the Junction Area, but not the right to take action to enforce its laws or regulations in that area. The concept of the Junction Area in fact resembles the ‘chimney’ concept of the 2001 agreement. 
This innovative and complex solution to the matter of Slovenian access to international waters, which includes an area without clear state adherence (for the Junction area is neither Slovenian, Croatian, nor international), has provoked responses in both Croatia and Slovenia. The right-wing opposition Slovenian Democratic Party (Slovenska Demokratska Stranka, SDS) commented that Slovenia gained only ‘a communication passage’ through Croatian waters, not ‘true access to the High Seas’. That means, they argue, that ‘Croatia has sold to Slovenia something that was already ours, when we became independent in 1991’.  The SDS had opposed the 2009 Arbitration Agreement and had even provoked a national referendum, that was held in June 2010. However, the majority of voters were in favour of the agreement so that the outcome of the referendum was a heavy defeat for the nationalists. Although the leaders of the SDS criticized the outcome of the international arbitration, they nonetheless admitted that Slovenia is entitled to respect the decision of the Tribunal in The Hague. Since the summer of 2017 Slovenian politics has managed to maintain a unified, if uncertain, position on the Arbitration. In October 2017 the SDS surprised Slovene society with an interpretation claiming that if Croatia should refuse to cooperate in implementing the decision within six months, Slovenia would no longer be obliged to respect the Tribunal’s decision.  However, after a session of the parliamentary commission for foreign policy in the same month the SDS changed its mind, and has since continued to support the Slovenian government on the matter. 
The SDS’s ideological equivalent in Croatia, the Croatian Democratic Union (Hrvatska demokratska zajednica, HDZ), which is currently leading the government, has not discussed the innovative solution of the Slovenian Junction to international waters. Instead, they have done their best to prove that the International Arbitration decision does not apply to Croatia.  Renowned and controversial Croatian international maritime law expert Davorin Rudolf, known for his fierce opposition to the 2009 Arbitration Agreement, described the Tribunal’s decision as ‘total amateurism’, and was especially appalled when Slovenia was given three quarters of the Bay of Piran. Regarding the Junction Area, Rudolf claimed that in the past Croatia had offered Slovenia a similar deal, but that the Slovenians had refused it. ‘Now, they are happy, but they have spent 6 million Euros in vain.’  A few months later, in September, Rudolf proposed jurisdiction shared between Croatia and Slovenia in the Bay of Piran—an idea not new in the history of the Slovenia-Croatia dispute. 
Meanwhile the Slovenian government continued to intensify its diplomatic pressure on Croatia. The Slovenian prime minister Miro Cerar tried to secure clear support from EU institutions and core EU political figures like Jean-Claude Juncker, President of the European Commission, and German Chancellor Angela Merkel.  The very fact that the German government supports the Slovenian position represents a huge challenge to Croatian leaders.  In October 2017 the Slovenian government prepared the draft of the legislation for the implementation of the arbitration ruling,  but Croatia has continued to ignore the decision of the Tribunal, in spite of the fact that reports appeared in both Croatian and Slovenian media that the Croatian government considers that the Tribunal’s ruling is at least not entirely unacceptable. Yet, as ‘unnamed diplomatic sources’ at the time stated, ‘regardless of the pressure, Croatia simply cannot go back, and Ljubljana must also be aware of this’. 
From a distance it is difficult to understand why Croatian politicians stubbornly refuse to acknowledge the Arbitration decision. Is it because they fear the Tribunal’s decision would prejudice open border questions with Bosnia and Herzegovina, Serbia, and Montenegro, the other post-Yugoslav states? The Arbitration Tribunal generally recognised the cadastral border—Croatia would certainly benefit from that principle as far as the border with Serbia on the Danube is concerned,  and regarding the Prevlaka/Oštra Peninsula too, on the border with Montenegro.  Is nationalism the only reason? In December 2017 the German public broadcasting station Zweites Deutsches Fernsehen (ZDF) interpreted the Croatian stance as a consequence of the war of 1991-95. In contemporary Croatia, claimed ZDF, the rule applies that not a single square centimetre of the Croatian homeland should be given away.  However, that interpretation underestimates the importance of Slovenian nationalism which, as the history of the dispute clearly proves, was decisive in shaping the conflict of the early 2000s. 
Slovenian authorities announced that after 29 December 2017 they would implement the Tribunal’s decision ‘as much as possible’ themselves. However, since it is not possible to delimitate the border without Croatian expert groups on the mainland, the Slovenian government decided to implement the new maritime border first. The Croatian government, which claims that the ‘true’ maritime border lies in the middle of the Bay of Piran, interpreted the Slovenian implementation as a violation of Croatian sovereignty.  Croatian fishermen continue to fish in disputed waters, accompanied by Croatian police boats. Almost every day a Slovenian police boat notifies a Croatian police boat, and the fishermen, that they have entered Slovenian territorial waters, whereupon the Croatian police notify the Slovenian police that they have entered the Croatian area. After these bizarre communications Slovenian police do not intervene further but leave the Croatian fishermen to their work.  The Slovenian government carefully documents such ‘violations of the rule of the Court of Arbitration in The Hague’. If Croatian refusal to abide by the Tribunal’s terms continues, Slovenia is determined to prosecute Croatia at the European Court of Justice.  Furthermore, Slovenia will continue to block Croatia’s requests for membership of the Organisation for Economic Cooperation and Development (OECD) and is even prepared to prevent Croatia’s inclusion in the Schengen area.  The implementation of the border arbitration is therefore becoming the most important ‘leitmotif’ of Slovenian foreign politics.
A number of Croatian political commentators see part of the reason for the refusal of the Tribunal decision as lying within internal Croatian politics. At the beginning of January 2018 notorious militant Croatian war veteran Petar Janjić-Tromblon surprised the Croatian public with an ultimatum to the Croatian prime minister, Andrej Plenković. Tromblon threatened to organise an expedition of ‘a hundred fishing boats’ onto the Bay of Piran if Plenković did not ‘solve the problem with Slovenia’ within 72 hours.  Of course, Tromblon did not carry out his threat, but the interference of war veterans has prompted interesting debate in the Croatian public sphere about the Croatian government’s integrity in its relations with militant war veterans. Denis Romac, a journalist with the newspaper Novi list was very clear on the subject, declaring ‘The state is not a state if it cannot stop Tromblon.’  Romac claimed that Tromblon’s threat should be seen in the context of pressure from right-wingers within the ruling Croatian party HDZ. 
How will the story end? One thing is certain; the official bilateral definition of precise borders demands two parties, so that Slovenia could scarcely implement the Tribunal rule by itself. Like so many of those horror films, the matter of the Slovenian-Croatian border has enormous potential to reinvent itself for the next episode. All we can predict for now is that Slovenia will continue to insist on the implementation of the Final Award, and that Croatia will try to find a way round it. Eventually, another innovative solution will have to be found which will somehow include the acceptance of the Court decision and simultaneously allay Croatian concerns about the arbitration process. The true question is whether or not the diplomats of both countries are both able and willing to invent such a solution? Until then Slovenian and Croatian leaders will continue to claim that their countries enjoy excellent relations—except on the question of the border between them.
About the author
Marko Zajc is a Research Associate at the Institute of Contemporary History in Ljubljana, Slovenia.
© 2018 Walter de Gruyter GmbH, Berlin/Boston