OPINION OF ADVOCATE GENERAL

PIKAMÄE

delivered on 11 December 2019 ( 1 )

Case C‑457/18

Republic of Slovenia

v

Republic of Croatia

(Failure of a Member State to fulfil obligations – Article 259 TFEU – Objections of lack of jurisdiction and inadmissibility – Establishment of the common boundary between two Member States – Boundary dispute between the Republic of Croatia and the Republic of Slovenia – Arbitration agreement – Arbitration proceedings – Notice given by the Republic of Croatia terminating the agreement – Partial and final arbitration awards made by the arbitral tribunal – Validity and effects of the ‘final arbitration award’)

1. Where a Member State brings an action for failure to fulfil obligations before the Court of Justice of the European Union under Article 259 TFEU, does the Court have jurisdiction to hear and determine that action if the claims that EU law has been infringed are based on the terms of an ‘arbitration award’, made under a bilateral arbitration agreement falling within public international law, but which one of the parties claims has no legal value whatsoever? That is the main question arising in the present case, one of the rare instances of an action between States for failure to fulfil obligations under Article 259 TFEU, ( 2 ) the first paragraph of which provides that a Member State ‘which considers that another Member State has failed to fulfil an obligation under the Treaties may bring the matter before the Court of Justice of the European Union.’

2. In its application, the Republic of Slovenia asks the Court of Justice, inter alia, to find that the Republic of Croatia has infringed Article 2 and Article 4(3) TEU and an entire series of provisions of secondary law concerning the common fisheries policy, the rules governing the movement of persons across borders (the Schengen Borders Code) and maritime spatial planning.

3. Before any substantive defence, the Republic of Croatia raised objections of lack of jurisdiction and inadmissibility in respect of the action to which this Opinion relates, and the Court decided to examine those objections separately before, if necessary, ruling on the substance of the case.

4. The Court must therefore examine whether the boundary dispute between the Republic of Croatia and the Republic of Slovenia, the attempt to resolve it and the resulting arbitration proceedings are matters of public international law that can serve as the basis of an action for failure to fulfil obligations under Article 259 TFEU. I will set out in this Opinion why in my view and as the Republic of Croatia claims, the Court does not have jurisdiction to rule on the present action. I also propose that the Court should uphold the Republic of Croatia’s request that the European Commission’s legal opinion contained in Annex C.2 to the Republic of Slovenia’s response be removed from the case file.

I. Legal context

A. International law

1. The arbitration agreement

5. The third recital in the preamble to the agreement signed on 4 November 2009 by the Republic of Croatia and the Republic of Slovenia (‘the arbitration agreement’) recalls the peaceful means for the settlement of disputes enumerated in Article 33 of the Charter of the United Nations. ( 3 ) Accordingly, Article 1 of the arbitration agreement sets up an arbitral tribunal.

6. Article 2 of that agreement establishes its composition and in particular the procedures for appointing and replacing its members.

7. Article 3 of the arbitration agreement, entitled ‘Task of the Arbitral Tribunal’, provides in paragraph 1 that the arbitral tribunal is to determine (a) the course of the boundary between Croatia and Slovenia, (b) Slovenia’s junction to the high sea, and (c) the regime for the use of the relevant maritime areas. Article 3(2) sets out the procedure for determining the subject matter of the dispute. Article 3(3) provides that the arbitral tribunal is to render an award on the dispute. According to Article 3(4), the arbitral tribunal has the power to interpret the arbitration agreement.

8. Under Article 4(a) of the arbitration agreement, when implementing the provisions of Article 3(1)(a) of that agreement, the arbitral tribunal is to apply the rules and principles of international law. According to Article 4(b) of the agreement, when implementing the provisions of Article 3(1)(b) and (c), the arbitral tribunal is to apply international law, equity and the principle of good neighbourly relations in order to achieve a fair and just result by taking into account all relevant circumstances.

9. Article 6(2) of the arbitration agreement provides that, unless envisaged otherwise, the arbitral tribunal will conduct the proceedings according to the Permanent Court of Arbitration (‘PCA’) Optional Rules for Arbitrating Disputes between Two States. Article 6(4) provides that the arbitral tribunal, after consultation of the parties, is to decide expeditiously on all procedural matters by majority of its members.

10. Article 7(1) of the arbitration agreement provides inter alia that the arbitral tribunal will issue its award expeditiously after due consideration of all relevant facts pertinent to the case. Article 7(2) stipulates that the arbitration award will be binding on the parties and will constitute a definitive settlement of the dispute. According to Article 7(3), the parties will take all necessary steps to implement the award, including by revising national legislation, as necessary, within six months after the adoption of the award.

11. Under Article 9(1) of the arbitration agreement, the Republic of Slovenia will lift its reservations as regards opening and closing of the EU accession negotiation chapters where the obstacle is related to the dispute.

12. Under Article 11(3) of the arbitration agreement, all procedural timelines expressed in the agreement will start to apply from the date when the Republic of Croatia signs the Treaty between the Member States of the European Union and the Republic of Croatia concerning the accession of the Republic of Croatia to the European Union ( 4 ) (‘the Accession Treaty’).

2. The Vienna Convention on the Law of Treaties

13. The Vienna Convention on the Law of Treaties of 23 May 1969 ( 5 ) (‘the Vienna Convention’) provides in paragraph 1 of Article 60, entitled ‘Termination or suspension of the operation of a treaty as a consequence of its breach’: ‘A material breach of a bilateral treaty by one of the parties entitles the other to invoke the breach as a ground for terminating the treaty or suspending its operation in whole or in part.’

B. EU law

1. The Act of Accession

14. Article 15 of the Act concerning the conditions of accession of the Republic of Croatia and the adjustments to the Treaty on European Union, the Treaty on the Functioning of the European Union and the Treaty establishing the European Atomic Energy Community ( 6 ) (‘the Act of Accession’), annexed to the Accession Treaty, provides: ‘The acts listed in Annex III shall be adapted as specified in that Annex.’

15. Annex III to the Act of Accession sets out in point 5 the adaptations to be made to the regulation on the common fisheries policy ( 7 ) applicable at the time of Croatia’s accession. Point 5 provides that points 11 and 12, entitled ‘Coastal waters of Croatia’ and ‘Coastal waters of Slovenia’ respectively, are added to Annex I to that regulation. Points 11 and 12 contain references to footnotes 2 and 3 according to which the ‘regime shall apply from the full implementation of the arbitration award resulting from the Arbitration Agreement between the Government of the Republic of Slovenia and the Government of the Republic of Croatia, signed in Stockholm on 4 November 2009.’

2. Secondary law

(a) Regulation (EU) No 1380/2013

16. Article 5 of Regulation (EU) No 1380/2013 of the European Parliament and of the Council of 11 December 2013 on the Common Fisheries Policy, ( 8 ) entitled ‘General rules on access to waters’, states in paragraphs 1 and 2: ‘1. Union fishing vessels shall have equal access to waters and resources in all Union waters other than those referred to in paragraphs 2 and 3, subject to the measures adopted under Part III. 2. In the waters up to 12 nautical miles from baselines under their sovereignty or jurisdiction, Member States shall be authorised, until 31 December 2022, to restrict fishing to fishing vessels that traditionally fish in those waters from ports on the adjacent coast, without prejudice to the arrangements for Union fishing vessels flying the flag of other Member States under existing neighbourhood relations between Member States and the arrangements contained in Annex I, fixing for each Member State the geographical zones within the coastal bands of other Member States where fishing activities are pursued and the species concerned. Member States shall inform the Commission of the restrictions put in place under this paragraph.’

17. Annex I to Regulation No 1380/2013, entitled ‘Access to coastal waters within the meaning of Article 5(2)’, refers in points 8 and 10, entitled ‘Coastal waters of Croatia’ and ‘Coastal waters of Slovenia’ respectively, to footnotes 2 and 3 according to which ‘the above mentioned regime shall apply from the full implementation of the arbitration award resulting from the Arbitration Agreement between the Government of the Republic of Slovenia and the Government of the Republic of Croatia, signed in Stockholm on 4 November 2009.’

18. The Republic of Slovenia also relies on the provisions of Council Regulation (EC) No 1224/2009 of 20 November 2009 establishing a Community control system for ensuring compliance with the rules of the common fisheries policy ( 9 ) and Commission Implementing Regulation (EU) No 404/2011 of 8 April 2011 laying down detailed rules for the implementation of Regulation No 1224/2009. ( 10 )

(b) Schengen Borders Code

19. Article 4 of Regulation (EU) 2016/399 of the European Parliament and of the Council of 9 March 2016 on a Union Code on the rules governing the movement of persons across borders (Schengen Borders Code) ( 11 ) (‘the Schengen Borders Code’), entitled ‘Fundamental Rights’, provides that ‘when applying this Regulation, Member States shall act in full compliance with relevant Union law, including … relevant international law, … obligations related to access to international protection’.

20. Article 13 of the Schengen Borders Code establishes border surveillance whose main purpose, according to Article 13(1), is ‘to prevent unauthorised border crossings, to counter cross-border criminality and to take measures against persons who have crossed the border illegally’. Article 13(2) to (5) of that code and Part A of Annex V determine the arrangements for that surveillance.

21. Article 17 of the Schengen Borders Code imposes an obligation of cooperation between Member States. Article 17(1) provides inter alia that the ‘Member States shall assist each other and shall maintain close and constant cooperation with a view to the effective implementation of border control, in accordance with Articles 7 to 16’ and ‘shall exchange all relevant information’.

(c) Directive 2014/89/EU

22. Recital 7 of Directive 2014/89/EU of the European Parliament and of the Council of 23 July 2014 establishing a framework for maritime spatial planning ( 12 ) states: ‘The United Nations Convention on the Law of the Sea of 1982 (“Unclos”) states in its preamble that issues relating to the use of ocean space are closely interrelated and need to be considered as a whole. Planning of ocean space is the logical advancement and structuring of obligations and of the use of rights granted under Unclos and a practical tool in assisting Member States to comply with their obligations.’

23. Article 2(4) of that directive states: ‘This Directive shall not affect the sovereign rights and jurisdiction of Member States over marine waters which derive from relevant international law, particularly Unclos. In particular, the application of this Directive shall not influence the delineation and delimitation of maritime boundaries by the Member States in accordance with the relevant provisions of Unclos.’

24. Article 11(1) of Directive 2014/89 provides: ‘As part of the planning and management process, Member States bordering marine waters shall cooperate with the aim of ensuring that maritime spatial plans are coherent and coordinated across the marine region concerned. Such cooperation shall take into account, in particular, issues of a transnational nature.’

II. Facts and pre-litigation procedure

25. On 25 June 1991, Slovenia and Croatia declared their independence from the Socialist Federal Republic of Yugoslavia. From 1992 to 2001, the Republic of Croatia and the Republic of Slovenia attempted to resolve the issue of the fixing of their land and maritime boundaries through bilateral negotiations.

26. The Republic of Slovenia became a member of the European Union on 1 May 2004.

27. On 4 November 2009, the Republic of Croatia and the Republic of Slovenia signed an arbitration agreement intended to resolve the boundary dispute between them, in which they undertook to be bound by the decision of an arbitral tribunal set up for that purpose. That agreement came into force on 29 November 2010.

28. On 9 December 2011, the Member States of the European Union and the Republic of Croatia signed the Accession Treaty. That treaty, ratified by the Republic of Croatia in January 2012, was published in the Official Journal of the European Union on 24 April 2012. The Republic of Croatia became a member of the European Union on 1 July 2013.

29. On 17 January 2012, pursuant to Article 2(1) of the arbitration agreement, the Republic of Croatia and the Republic of Slovenia appointed the president and two members of the arbitral tribunal. ( 13 ) The two further members of the tribunal who had to be appointed by the parties, under Article 2(2) of the arbitration agreement, were appointed at the end of January 2012. ( 14 ) The terms of appointment were signed in April 2012 and the Permanent Court of Arbitration (‘PCA’) ( 15 ) was appointed to act as Registry ( 16 ) by both the States in question. ( 17 ) Furthermore, under Article 6(2) of the arbitration agreement, the arbitral tribunal was obliged to conduct the proceedings according to the PCA Optional Rules for Arbitrating Disputes between Two States. ( 18 )

30. The written procedure commenced on 11 February 2013 and the hearing was held from 2 to 13 June 2014.

31. It is apparent from the written submissions of the Republic of Croatia that a procedural issue arose during the arbitration proceedings, resulting from an ex parte communication during the arbitral tribunal’s deliberations between the arbitrator appointed by the Republic of Slovenia and that State’s agent acting before the arbitral tribunal. Following the publication of certain articles in the press, the two people concerned resigned their appointments as arbitrator and agent. On 30 July 2015, the arbitrator originally appointed by the Republic of Croatia also resigned.

32. By letter sent to the arbitral tribunal on 24 July 2015, the Republic of Croatia informed the tribunal that it was extremely concerned about the ex parte communication at issue, which, in its view, cast serious doubt on the integrity and impartiality of the arbitration proceedings as a whole, and applied for the proceedings before the arbitral tribunal to be temporarily suspended. ( 19 )

33. On 29 July 2015, the Parliament of the Republic of Croatia unanimously adopted a resolution on the obligation of the Government of the Republic of Croatia to commence a procedure to terminate the arbitration agreement.

34. By note verbale of 30 July 2015, the Republic of Croatia notified the Republic of Slovenia that it considered itself entitled to terminate the arbitration agreement ( 20 ) on the ground of a material breach of that agreement by the Republic of Slovenia, for the purposes of Article 60(1) of the Vienna Convention. The Republic of Croatia stated that the note verbale constituted a notification, pursuant to Article 65(1) of the Vienna Convention, by which it proposed to terminate the arbitration agreement forthwith. The Republic of Croatia explained that in its view the impartiality and integrity of the arbitral proceedings had been irrevocably damaged, giving rise to a manifest violation of its rights. The arbitral tribunal received a copy of that note verbale.

35. By letter of 31 July 2015, the Republic of Croatia informed the arbitral tribunal that it had decided to terminate the arbitration agreement, explaining the reasons for so doing.

36. The Republic of Slovenia appointed a new arbitrator, who nevertheless resigned on 3 August 2015. The president of the arbitral tribunal subsequently appointed two new arbitrators to the two vacant posts in accordance with the procedure for the replacement of an arbitrator under Article 2 of the arbitration agreement.

37. By letter of 1 December 2015, the arbitral tribunal invited both parties to make new written and oral submissions ‘concerning the legal implications of the matters set out in [the Republic of] Croatia’s letters of 24 July 2015 and 31 July 2015’. The arbitral tribunal directed both parties to file their written submissions no later than 15 January 2016 (the Republic of Croatia) and 26 February 2016 (the Republic of Slovenia). In addition, the arbitral tribunal informed both parties that it intended to hold a hearing on those issues on 17 March 2016.

38. A hearing on those issues took place on 17 March 2016. The Republic of Slovenia filed a written memorial and participated in the hearing. The Republic of Croatia, for its part, did not participate in the hearing.

39. On 30 June 2016, the arbitral tribunal ruled on the procedural question by means of a partial award. The arbitral tribunal found, inter alia, that, by engaging in ex parte contact with the arbitrator originally appointed by it, the Republic of Slovenia had acted in breach of the arbitration agreement. Nevertheless, the nature of those breaches did not entitle the Republic of Croatia to terminate the arbitration agreement, which continued to apply. According to the arbitral tribunal, those breaches did not affect the ability of the arbitral tribunal, in its new composition, to issue an independent and impartial final award. The arbitral tribunal therefore found that there was no obstacle to the continuation of the proceedings under the arbitration agreement.

40. On 29 June 2017, the arbitral tribunal made a final arbitration award determining the land and maritime boundaries of the two States, which the Republic of Croatia claims is invalid and therefore of no binding effect.

41. On 16 March 2018, the Republic of Slovenia commenced the procedure provided for in Article 259 TFEU by making a complaint to the Commission alleging that the Republic of Croatia had infringed EU law.

42. The Commission did not issue a reasoned opinion within the three month period provided for in Article 259 TFEU.

III. Procedure before the Court and forms of order sought

43. The Republic of Slovenia commenced the present action by document lodged at the Court Registry on 13 July 2018.

44. By a separate document of 21 December 2018, the Republic of Croatia submitted an objection of inadmissibility against the present action, under Article 151 of the Rules of Procedure of the Court of Justice. The Republic of Croatia claims that the action should be dismissed in its entirety as inadmissible, on the ground that, under Article 259 TFEU, the Court lacks jurisdiction to rule on the form of order sought by the Republic of Slovenia. In the alternative, it makes the same claim on the ground that the application does not comply with Article 21 of the Statute of the Court of Justice of the European Union and Article 120 of the Rules of Procedure of the Court of Justice.

45. The Republic of Slovenia filed its observations on that objection on 12 February 2019. It contends that the action is admissible, arguing, in essence, that the Court of Justice has jurisdiction to rule on the present action on the basis of Article 259 TFEU and that the action satisfies the requirements under Article 21 of the Statute of the Court of Justice of the European Union and Article 120 of the Rules of Procedure of the Court of Justice.

46. By decision of 14 May 2019, the Court referred the case to the Grand Chamber to rule on the objection of inadmissibility.

47. By letter of 7 June 2019 from the Court Registry, the Court requested the Commission, pursuant to the second paragraph of Article 24 of the Statute of the Court of Justice of the European Union, to reply in writing or, as applicable, at the hearing to questions relating to the provisions of Regulation No 1380/2013.

48. By letter of 31 May 2019, the Republic of Croatia requested the Court to remove from the case file the Commission’s internal working document relating to the opinion of its Legal Service, contained in Annex C.2 to the Republic of Slovenia’s response to the objection of inadmissibility. ( 21 )

49. By letter of 20 June 2019 from the Court Registry, the Court requested the Commission to file its observations on that request.

50. The Commission filed those observations on 28 June 2019. In a separate letter, on the same day, the Commission answered the questions sent to it on 7 June 2019.

51. A hearing was held on 8 July 2019, at which the Republic of Croatia and the Republic of Slovenia were present, duly represented.

52. When asked at the hearing, the Republic of Slovenia stated that it maintained its application that the alleged infringements be put to an end.

IV. The arguments of the Republic of Slovenia set out in the application

53. In support of its action, the Republic of Slovenia advances six complaints in its application.

54. By its first complaint, the Republic of Slovenia claims that, by unilaterally defaulting on the commitment, which it made during the process of accession to the European Union, to comply with the forthcoming arbitration award, the boundary delimited by the arbitration award at issue and the other obligations arising under that award, the Republic of Croatia, in breach of Article 2 TEU, is refusing to respect the value of the rule of law and the principles of sincere cooperation and res judicata.

55. By its second complaint, the Republic of Slovenia argues that, by unilaterally refusing to fulfil its obligations under the arbitration award at issue, the Republic of Croatia is preventing it from fully exercising its sovereignty throughout its mainland and maritime territory in compliance with the Treaties and rules of secondary law. By so doing, it is in breach of the duty of sincere cooperation laid down in Article 4(3) TEU and is jeopardising the attainment of the objectives of the European Union (including promoting and building peace, and an ever closer union between nations), the attainment of the objectives of the EU rules relating to the territory of the Member States, and the effective implementation of EU law by the Republic of Slovenia. In that context, the Republic of Slovenia alleges that the Republic of Croatia is preventing it from fulfilling its obligation to implement a whole series of acts of secondary law. ( 22 )

56. By its third complaint, the Republic of Slovenia claims that, by failing to respect either Slovenian territory or boundaries, the Republic of Croatia is infringing EU law in relation to the common fisheries policy.

57. The Republic of Slovenia submits in that respect that, by disputing the boundary as determined by the arbitration award at issue and objecting to the demarcation and application of that boundary, the Republic of Croatia is infringing the Republic of Slovenia’s exclusive rights over its territorial waters and is preventing it from complying with its obligations under Regulation No 1380/2013.

58. In particular, the Republic of Slovenia criticises the Republic of Croatia for infringing the reciprocal access regime set up by Regulation No 1380/2013, which has applied to both those Member States since 30 December 2017 and grants 25 vessels of each of those Member States free access to the other Member State’s territorial sea as determined according to international law, that is to say, the arbitration award at issue. It alleges that the Republic of Croatia is preventing implementation of the reciprocal access regime, is refusing to recognise the validity of the legislation adopted by the Republic of Slovenia for that purpose and, by systematically applying fines to them, is denying Slovenian fishermen free access to the territorial waters which the arbitration award at issue has defined as Slovenian and, a fortiori, free access to the Croatian waters falling within the scope of that regime.

59. By its fourth complaint, the Republic of Slovenia claims that the Republic of Croatia is infringing the Community control system established by Regulation No 1224/2009 and Implementing Regulation No 404/2011 for ensuring compliance with the rules of the common fisheries policy (‘the control system’) given that, first, the Republic of Croatia is preventing it from complying with its obligations under the control system and, secondly, the Republic of Croatia is unlawfully exercising in Slovenian waters rights that belong to the Republic of Slovenia as the coastal State. Those regulations impose two series of obligations on flag Member States, that is to say, a monitoring obligation (Article 9(3) of Regulation No 1224/2009 and Articles 21 to 23 of Implementing Regulation No 404/2011) and an obligation to communicate data (Article 15 of Regulation No 1224/2009 and Articles 43 and 44 of Implementing Regulation No 404/2011).

60. By its fifth complaint, the Republic of Slovenia claims that the Republic of Croatia is infringing the Schengen Borders Code, given that the boundary between the two States is still an external border to which the provisions of Title II of that code apply. The Republic of Croatia is infringing both the border control obligations under Article 17 of the Schengen Borders Code and the border surveillance obligation laid down by Article 13 of that code. Furthermore, in refusing to recognise the arbitration award at issue, it is failing to fulfil the obligation laid down in Article 4 of that code to act in full compliance with the relevant provisions of the applicable international law.

61. By its sixth complaint, the Republic of Slovenia alleges that, by refusing to recognise the arbitration award at issue establishing the delimitation of the territorial waters between the two Member States, and by including Slovenian territorial waters in its maritime spatial planning, ( 23 ) the Republic of Croatia is infringing Article 4(1) and Article 8 of Directive 2014/89. By so doing, the Republic of Croatia makes any cooperation impossible, thereby infringing Article 11(1) of that directive which establishes the obligation of cooperation.

V. Summary of the arguments of the parties on the objections of lack of jurisdiction and inadmissibility

A. Grounds of challenge alleging that the Court of Justice lacks jurisdiction to hear and determine the present case

62. The first ground of challenge relating to lack of jurisdiction alleges that the claims made by the Republic of Slovenia are ancillary. According to the Republic of Croatia, those claims, as they appear in the application, are ancillary to resolution of the dispute concerning the validity and legal effects of the arbitration agreement and of the arbitration award at issue. In proceedings under Article 259 TFEU, the Court of Justice has no jurisdiction to rule either on that dispute or on any such ancillary claims. The judgment in Commission v Belgium ( 24 ) shows that, in such proceedings, the Court does not have jurisdiction to rule on the infringement of obligations under EU law if those obligations are ancillary to the prior settlement of a different dispute over which the Court does not have jurisdiction.

63. By its second ground of challenge relating to lack of jurisdiction, the Republic of Croatia contends that the true subject matter of the dispute between the two States consists of, first, the interpretation and applicability of the arbitration agreement, which does not form an integral part of EU law, and, secondly, the validity and any legal effects of the arbitration award at issue.

64. The Republic of Croatia emphasises in that respect that it disputes the very existence of the arbitration award at issue, since it validly terminated the arbitration agreement before that award was even made. Were the Court to examine those matters, it would have to address in particular, first, the issue of the validity of that termination and its effects, secondly, whether, after the termination at issue, the arbitral tribunal continued to exist, thirdly, whether that tribunal was entitled to decide whether it continued to exist and, fourthly, whether the termination at issue ended the work of the arbitral tribunal. ( 25 ) Furthermore, if it did examine those questions, the Court would have to assess the grounds in the partial award. However, those questions are matters of international law and, in particular, concern the interpretation of Article 60 of the Vienna Convention and of the arbitration agreement, which do not form an integral part of EU law.

65. By its third ground of challenge relating to lack of jurisdiction, the Republic of Croatia asserts that the Court does not have jurisdiction, under Article 259 TFEU, to rule either on the validity and effects of the arbitration agreement, on the ground that the agreement does not form an integral part of EU law, or on the validity and effects of the arbitration award at issue purportedly made on the basis of that arbitration agreement. According to the Republic of Croatia, any effect that resolution of the bilateral dispute may have on the functioning of EU law cannot extend the Court’s jurisdiction beyond what is laid down in the Treaties. The Republic of Slovenia’s complaints relating to infringements of EU law, but whose resolution depends on prior settlement of the dispute relating to the validity and any legal effects of the arbitration agreement, are therefore insufficient to give the Court jurisdiction to hear and determine this dispute under Article 259 TFEU.

66. By its fourth ground of challenge relating to lack of jurisdiction, the Republic of Croatia claims that, in contrast to a dispute put to the Court under Article 273 TFEU, the present dispute is not required merely to relate to EU law. The Republic of Slovenia’s complaints relating to infringements of EU law, which, however, depend on prior settlement of the dispute relating to the validity and any legal effects of the arbitration agreement, are therefore insufficient to give the Court jurisdiction to hear and determine this dispute under Article 259 TFEU.

67. By its fifth ground of challenge relating to lack of jurisdiction, the Republic of Croatia argues that any finding by the Court that the Republic of Croatia committed the purported infringements of EU law would be at the very most hypothetical. The Court does not have jurisdiction to rule on hypothetical infringements of EU law in proceedings under Article 259 TFEU.

68. By its sixth ground of challenge relating to lack of jurisdiction, the Republic of Croatia submits that this dispute does not raise any question of interpretation of EU law. It therefore cannot be argued in the present case that the Court has jurisdiction under Article 259 TFEU as a result of the need to resolve a dispute relating to the interpretation of EU law and to ensure uniform application of that law in that way.

69. The Republic of Slovenia claims that the Republic of Croatia’s objection of lack of jurisdiction should be rejected.

70. In the first place, it contends that the objection is based on the false premiss that its application is seeking a finding that the Republic of Croatia failed to fulfil its obligations under the arbitration agreement or the arbitration award at issue, but not under EU law. This is an attempt by the Republic of Croatia unilaterally to misrepresent the subject matter of the action.

71. In that respect the Republic of Slovenia submits, first, that it follows from the provisions of the Treaties and the case-law that the Court’s jurisdiction depends on the fact that, in the form of order sought in the application, the applicant State pleads an infringement of EU law or on the fact that EU law applies to that form of order. The Republic of Croatia cannot for its own benefit alter how the subject matter of the action is presented in the application, given that in the form of order sought in its application the Republic of Slovenia does not ask the Court in the slightest to find that the Republic of Croatia has failed to fulfil its obligations under international law, but asks it to find a failure to fulfil obligations owed by that Member State under EU law.

72. Secondly, the Republic of Slovenia contends that the Court is not prevented from having jurisdiction under Article 259 TFEU where the facts on which the alleged infringements of EU law are based also fall within the scope of international law. All that matters, in that respect, is that those facts relate to an infringement of obligations imposed by EU law. That does not, however, prevent the Court from having regard to substantive rules of international law that EU law has included or intended to include in its legal order.

73. Thirdly, the Republic of Slovenia submits that the existence of a bilateral dispute concerning the interpretation of an act of international law applicable between the parties to proceedings for failure to fulfil obligations likewise does not preclude the Court from having jurisdiction. Accordingly, in the judgment in Spain v United Kingdom, ( 26 ) the Court interpreted a unilateral declaration by the United Kingdom reflecting the contents of an agreement between the Kingdom of Spain and the United Kingdom, even though there was a dispute between the parties concerning the meaning of that instrument of international law.

74. Fourthly, in order to rule on whether an action under Article 259 TFEU is admissible, it is only necessary to determine whether the basis of the form of order sought corresponds to ‘obligations under the Treaties’. The Republic of Croatia is mistaken in suggesting that, in order to find that it has jurisdiction, the Court must be persuaded that a Member State has infringed its obligations under the Treaties. The interpretation and application of the rules of EU law are not questions that the Court should examine at that stage. They are, on the contrary, a matter for the examination on the merits.

75. In the second place, as regards the first ground of challenge relating to lack of jurisdiction, alleging that the claims concerning EU law are ancillary, the Republic of Slovenia submits that the Court is not required, in order to rule on the alleged infringements of EU law, to rule on a failure to fulfil obligations under international law or on acts contrary to international law committed by the Republic of Croatia. Given that the territories of the Republic of Croatia and of the Republic of Slovenia respectively are determined by the boundary set in accordance with international law, that is to say, the arbitration award at issue, it is therefore not incumbent on the Court either to find that international law has been infringed or to rule on an international dispute.

76. As regards the second ground of challenge relating to lack of jurisdiction, alleging that the ‘true’ subject matter of the dispute is the interpretation of international law, the Republic of Slovenia asserts that the boundary between it and the Republic of Croatia is a matter of fact in respect of which the Court can rely on the outcome of the resolution of the territorial dispute and not a matter of law on which the Court might rule. The Court should, on the other hand, respect and apply international law, in so far as necessary in order to interpret or apply EU law.

77. In respect of the third ground of challenge relating to lack of jurisdiction, alleging that the dispute concerning the validity and any legal effects of the arbitration agreement should have been settled previously, the Republic of Slovenia asserts that, in order to determine the extent of and compliance with the obligations on the Member States under EU law, including the obligation not to prevent another Member State from implementing and applying EU law in its own territory, the starting point must be the boundary between the Member States concerned, as established under international law. The Court must have regard to the existing elements of international law, as facts.

78. The Republic of Slovenia adds that whether or not the arbitration agreement and the legal effects of the arbitration award at issue are valid is not the subject matter of the dispute before the Court, does not fall within its jurisdiction and, in any event, has been resolved in the partial award of the arbitral tribunal. The fact that the arbitration award at issue is not satisfactory to the Republic of Croatia does not mean that there is an unresolved boundary dispute or that the Court should rule on that question, which has already been determined.

79. Furthermore, the Republic of Croatia’s argument that the arbitration award at issue is not directly applicable – besides being not a matter of admissibility but for examination on the merits – is incorrect, since that award is binding under international law, and definitively establishes the boundary between the two Member States.

80. As regards the fifth ground of challenge relating to lack of jurisdiction, concerning the hypothetical nature of the infringements of EU law alleged against it, according to the Republic of Slovenia the Republic of Croatia merely states that it did not fail to fulfil its obligations under EU law. Such an argument in fact goes to the substance of the case. In any event, this is a matter of actual rather than hypothetical infringements that are occurring daily and which the Republic of Slovenia is trying to bring to an end by means of the present action under Article 259 TFEU.

81. As regards the sixth ground of challenge relating to lack of jurisdiction, alleging that the present case does not raise any questions of interpretation of EU law, because the parties share the same understanding of their obligations under EU law, the Republic of Slovenia asserts that the existence of a dispute concerning the interpretation or application of EU law is not, inherently, a precondition for the Court to have jurisdiction under Article 259 TFEU. It is sufficient for the Republic of Slovenia to claim that the Republic of Croatia has failed to fulfil its obligations under EU law.

B. Grounds of challenge alleging that the application is inadmissible

82. In the alternative, in the event that the Court finds that it does have jurisdiction to hear and determine this dispute, the Republic of Croatia claims that the application, which does not comply with the requirements of Article 21 of the Statute of the Court of Justice of the European Union and Article 120 of the Rules of Procedure of the Court of Justice, must be dismissed as inadmissible. In the form of order that it seeks in the application, the Republic of Slovenia does not expressly indicate the subject matter of the dispute, which according to the Republic of Croatia is a failure by the Republic of Croatia to fulfil its obligations under the arbitration award at issue. According to the Republic of Croatia, the form of order sought does not mention a purported infringement of the arbitration award at issue, and the application does not set out any legal arguments showing that there is a valid arbitration award, with the effect that the Republic of Croatia is unable to prepare its defence and reply to those arguments.

83. The Republic of Slovenia contends that the action satisfies all the requirements of Article 21 of the Statute of the Court of Justice of the European Union and Article 120 of the Rules of Procedure of the Court of Justice. The subject matter of the action is properly and precisely defined, summarised at the beginning of the application, developed and supported by precise facts and clear arguments, and is mentioned once again in the form of order sought in the application. The alleged infringements of EU law are defined precisely and do not generate any doubt.

84. The Republic of Croatia’s assertion that it is unable to prepare its defence against the allegation of infringement of the arbitration award at issue is therefore, according to the Republic of Slovenia, also incorrect. Even assuming that the Court has to take that allegation into account, it relates to the substance of the case rather than to its admissibility.

C. The request that the opinion of the Commission’s Legal Service be removed from the proceedings

85. The Republic of Croatia has requested the Court, in accordance with Article 151 of the Rules of Procedure of the Court of Justice, to remove from the case file the Commission’s legal opinion contained at pages 38 to 45 of Annex C.2 to the Republic of Slovenia’s response to the objection of inadmissibility (‘the legal opinion at issue’).

86. In support of its request, the Republic of Croatia claims that the legal opinion at issue is an internal document that the Commission has never made public. Unauthorised dissemination of that opinion could, according to the Commission, adversely affect its smooth functioning.

87. The Commission, relying on the order of 23 October 2002 in Austria v Council, ( 27 ) contends that to produce internal documents of that nature in proceedings before the Court, unless such production has been authorised by the institution concerned or ordered by the Court, would be contrary to the public interest in institutions being able to receive the advice of their legal services, given in full independence. According to the Commission, the legal opinion at issue is an internal document that was not intended to be published and to which the public was not given access. The Commission states that production of the opinion in proceedings before the Court was not authorised. The legal opinion at issue should therefore be removed from the case file.

VI. Analysis

88. The Republic of Croatia contends that the Court has no jurisdiction to rule on the action for failure to fulfil obligations and, in the alternative, that the action is inadmissible on the ground that it does not comply with the requirements under Article 21 of the Statute of the Court of Justice of the European Union and Article 120 of the Rules of Procedure of the Court of Justice. I would indicate at this stage that, for the reasons set out below, I believe that the Court does not have jurisdiction to examine the present action and that it is therefore unnecessary to analyse whether it is admissible in the light of any failure to comply with the abovementioned provisions.

89. First, before examining the grounds of challenge relating to lack of jurisdiction and inadmissibility, it is necessary to examine the request that the opinion of the Commission’s Legal Service be removed from the proceedings (section A). Secondly, in the context of examining the Court’s jurisdiction, it seems to me necessary (i) to make a number of preliminary remarks on the Court’s jurisdiction, in particular where international legal instruments are involved (section B), and (ii) to examine the subject matter of the action in the light of those remarks, analysing the specific complaints advanced by the applicant (section C).

A. The request that the opinion of the Commission’s Legal Service be removed from the proceedings

90. The Republic of Croatia has requested the Court under Article 151 of the Rules of Procedure of the Court of Justice to remove the legal opinion at issue from the case file.

91. First, it must be noted that, by its order of 23 October 2002 in Austria v Council, ( 28 ) the Court ordered that the opinion of the Commission’s Legal Service produced as an annex to Austria’s application for annulment of a regulation should be removed from the case file. In paragraph 12 of that order, the Court stated in particular that it would be contrary to public policy, which requires that the institutions can receive the advice of their legal service, given in full independence, to allow such internal documents to be produced in proceedings before the Court unless such production has been authorised by the institution concerned or ordered by the Court.

92. In the present case, it should be noted that the legal opinion in question comes from the Commission’s Legal Service and was prepared for the attention of the Head of Cabinet of the Commission’s President. That opinion was prepared in the context of the procedure that was initiated by the Republic of Slovenia under the second paragraph of Article 259 TFEU for the purpose of first bringing the matter before the Commission. The opinion contains an analysis of the claims made against the Republic of Croatia, with the aim of obtaining the Head of Cabinet’s agreement to preparing a reasoned opinion under the third paragraph of Article 259 TFEU. It is clear that the legal opinion at issue was not intended to be published. ( 29 )

93. Secondly, according to the case-law, removal of an institution’s legal opinion is justified where there is a foreseeable risk of the institution concerned being obliged, in the pending court proceedings relating to the validity of a decision made by that institution, publicly to adopt a position in respect of the opinion issued by its own legal service. That prospect would inevitably have adverse repercussions on the interest of the institution concerned in seeking legal advice and its ability to receive frank, objective and comprehensive advice from its legal service. ( 30 )

94. In the present instance, in the procedure provided for in the second paragraph of Article 259 TFEU, the Commission, after the matter was brought before it by the Republic of Slovenia, did not issue a reasoned opinion under the third paragraph of that article. It has therefore not expressed its official position on that procedure. The present case can therefore be distinguished from the abovementioned cases, which concerned court proceedings relating to the validity of a decision adopted and defended by the institution concerned. Nevertheless, despite that distinction, I believe that the considerations expressed in point 93 of this Opinion are relevant, mutatis mutandis, to the present case. Indeed, it is not inconceivable that the Commission may subsequently decide to intervene in the proceedings before the Court or that it may be requested to submit observations, with the consequence that it would have to express its official opinion on the case brought before the Court and therefore take a position publicly on the advice issued by its own legal service. It therefore appears that removal of the legal opinion at issue is justified in the light of that institution’s interest in seeking and receiving frank, objective and comprehensive advice from its Legal Service. ( 31 )

95. Furthermore, the Court of Justice has already held that to allow a Member State to include in the case file a legal opinion whose disclosure has not been authorised by the institution at issue would be tantamount in particular to circumventing the procedure for requesting access to such a document under Regulation No 1049/2001. ( 32 ) In the present case, as the Commission stated in its written observations, the legal opinion at issue was not made accessible to either the parties or the public, but was disclosed as an annex to a press article. ( 33 ) It must therefore be found that the Republic of Slovenia did not obtain the legal opinion at issue in accordance with the procedures laid down by Regulation No 1049/2001.

96. In those circumstances, and bearing in mind that the Commission informed the Court that it did not wish the document in question to be produced in the present action, I propose that the request of the Republic of Croatia seeking removal from the case file of the document appearing at pages 38 to 45 of Annex C.2 to the Republic of Slovenia’s response to the objection of inadmissibility should be granted.

B. Preliminary remarks on the jurisdiction of the Court of Justice

97. It is necessary, first of all, to make a few preliminary remarks about the Court’s jurisdiction over actions for failure to fulfil obligations (1), secondly, to determine the scope ratione materiae of EU law where international legal instruments are involved (2) and, thirdly, to examine the territorial scope of EU law (3).

1. The Court’s jurisdiction over actions for failure to fulfil obligations

98. Under Article 19 TEU the Court is responsible for ensuring that the law is observed in the interpretation and application of the Treaties. ( 34 ) Under Article 19(3)(a), the Court is to rule in accordance with the Treaties on actions brought by a Member State, an institution or a natural or legal person. That jurisdiction is embodied in the action for failure to fulfil obligations under Article 259 TFEU.

99. The procedure pursuant to Article 259 TFEU is designed to obtain a declaration that the conduct of a Member State is in breach of EU law and to terminate that conduct. ( 35 ) Under that provision, the jurisdiction of the Court to declare that there is an infringement by a Member State is conditional on there being a failure to fulfil ‘an obligation under the Treaties’. In that context, it is not for the Court to consider what objectives are pursued in an action for failure to fulfil obligations brought before it. ( 36 )

100. In the expression ‘obligation under the Treaties’, the word ‘Treaties’ implies that an action can be brought for alleged infringements of the EU and FEU Treaties and of the Charter of Fundamental Rights of the European Union, provided that the Member State’s conduct falls within their scope. ( 37 ) It is furthermore clear that the expression also refers to measures of secondary law. ( 38 )

101. The Court’s jurisdiction therefore depends on the scope of EU law. ( 39 ) Since the present case concerns an international arbitration agreement and an arbitration award under that agreement, I propose to examine the scope ratione materiae of EU law where international legal instruments are involved.

2. Scope ratione materiae of EU law where legal instruments of international law are involved

102. Since the arbitration agreement and the arbitration award at issue, on which the present action turns, are instruments of international law, it is necessary to determine their relationship with EU law, whether they form an integral part of the EU legal order and whether the European Union is bound by them.

(a) Instruments of international law in the case-law of the Court

103. According to settled case-law, ‘the European Union is bound, … when exercising its powers, to observe international law in its entirety, including not only the rules and principles of general and customary international law, but also the provisions of international conventions that are binding on it’. ( 40 )

104. It is to my mind apparent from that case-law that the situations in which the European Union is bound by international law are very limited. First, the European Union is bound by international agreements concluded by it pursuant to the provisions of the Treaties, which are, from the date of their entry into force, an integral part of the EU legal order. ( 41 ) Secondly, the European Union is bound by an international convention where it has assumed the powers previously exercised by the Member States in the field to which that convention applies. ( 42 ) Thirdly, the European Union must respect customary international law in the exercise of its powers. ( 43 ) It follows that international conventions that do not fall within the categories referred to above are not acts of the European Union and do not bind it. Since they are not a matter of EU law, the Court of Justice has no jurisdiction to examine their validity or to interpret them.

(b) The ancillary nature of the claims relating to obligations under EU law

105. In support of its first ground of challenge relating to lack of jurisdiction, the Republic of Croatia submitted that the judgment in Commission v Belgium ( 44 ) shows that, in an action for failure to fulfil obligations, the Court does not have jurisdiction to rule on the alleged infringement of obligations under EU law ‘if those obligations are ancillary to the prior settlement of a different dispute over which the Court does not have jurisdiction’.

106. To my mind, it is apparent from Commission v Belgium that, in the context of an action for failure to fulfil obligations, the involvement of instruments of international law, which are not EU acts, can adversely affect the Court’s jurisdiction to examine an alleged infringement of EU law. The situation concerns an alleged failure to fulfil obligations, which formally relates to EU law but, in actual fact, concerns an instrument of international law that falls outside the scope ratione materiae of EU law and therefore the jurisdiction of the Court. Accordingly, in that judgment, the Court held that it did not have jurisdiction to rule on the alleged infringement of obligations under EU law that were merely ancillary to those under an instrument of international law.

107. More specifically, in that case, the Commission alleged infringement both of the 1962 Establishment Agreement, concluded on 12 October 1962 between the Board of Governors of the European School and the Government of the Kingdom of Belgium, and of Article 10 EC (now Article 4(3) TEU). The Court analysed the substance of the application initiating proceedings, which enabled it to assess the exact scope of the Commission’s complaint against the Kingdom of Belgium. The Court found that the infringement of the provision of EU law was merely the consequence of failure by the Member State concerned to fulfil its obligations under that establishment agreement, and formally reflected that finding in the term ‘ancillary’ applied to the alleged infringement of Article 10 EC. Having found, on conclusion of a second analysis, that the agreement in question did not form part of EU law but fell within international law alone, the Court logically held that it had no jurisdiction to rule on the action for failure to fulfil obligations brought by the Commission.

108. I believe that the reasoning expounded in that judgment is significant for the present case. I therefore propose to examine the criteria set out in that judgment in my analysis of the specific complaints advanced by the applicant in support of the action (section C below).

3. The territorial scope of EU law

109. It must be noted that, according to the form of order sought in the application, the Court has not formally been asked to assess whether the arbitration agreement applies or whether the arbitration award at issue is valid, but is called upon to rule on whether provisions of EU law, such as Article 2 and Article 4(3) TEU and those relating to the common fisheries policy, the Schengen Borders Code and maritime spatial planning, have been infringed by the Republic of Croatia and are therefore applicable in the present case.

110. In that regard, the European Union, unlike a State, does not have either ‘territorial jurisdiction’ under international law, that is to say, any rights to exercise sovereignty over its territory, or any ‘EU territory’ comparable to ‘federal territory’. ( 45 )‘EU territory’ is in fact the geographical space referred to in Article 52 TEU and Article 355 TFEU which define the territorial scope of the Treaties. ( 46 ) Specifically, Article 52 TEU provides, in its first paragraph, that the Treaties are to apply to the Member States. ( 47 ) The detailed rules governing the territorial scope of the Treaties are laid down in Article 355 TFEU. Article 52 TEU and Article 355 TFEU are relevant not only to determining the external border of the European Union, but also to establishing the respective competences of the Member States to implement EU law. To that effect, in Aktiebolaget NN, ( 48 ) the Court held, in relation to Article 299 EC, now Article 355 TFEU, that, ‘in the absence, in the Treaty, of a more precise definition of the territory falling within the sovereignty of each Member State, it is for each of the Member States to determine the extent and limits of that territory, in accordance with the rules of international public law.’ ( 49 )

111. The territorial scope of EU law is therefore not determined a priori by the European Union but is instead an objective fact that it has to accept. It follows that, in an action brought under Article 259 TFEU, such as that in the present case, in which a Member State is alleged to be impeding the implementation of EU law on the territory of another Member State, delimitation of the territory covered by the jurisdiction of a Member State does not fall within the sphere of competence of the European Union, which must, in that respect, look to public international law and the EU instruments in conformity with that law that define the extent of that territory.

4. Interim conclusion

112. In the light of the foregoing, in my view the Court’s jurisdiction in an action for failure to fulfil obligations depends on the scope of EU law. EU law involves, first, two series of treaty-based international rules, that is to say, the international conventions concluded by the European Union pursuant to the provisions of the Treaties and those where the European Union has assumed the powers previously exercised by the Member States in the field to which the conventions in question apply, and, secondly, the customary rules of public international law that are binding on the European Union in the exercise of its powers. In the context of actions for failure to fulfil obligations, ( 50 ) the Court does not, on the other hand, have jurisdiction to resolve disputes between Member States relating to the validity, interpretation and application of international conventions that do not fall within EU law. The Court has for that reason held that it had no jurisdiction in a situation in which the application formally related to EU law, whereas the alleged infringement in fact related to an instrument of international law falling outside the scope ratione materiae of EU law and therefore the jurisdiction of the Court, meaning that the complaints alleging infringement of EU law were ancillary. The territorial scope of the Treaties is defined in Article 52 TEU and Article 355 TFEU and is an objective fact predetermined by the Member States which the European Union has to accept. Indeed, in the absence, in the Treaties, of a more precise definition of the territory falling within the sovereignty of each Member State, it is for each of them to determine the extent and limits of that territory, in accordance with the rules of public international law. Since, in the context of an action for failure to fulfil obligations, the Court has jurisdiction only to rule on the conduct of a Member State that is in breach of EU law, it has no jurisdiction to examine inter-State territorial disputes.

C. Subject matter of the action

113. In order to determine, in the light of the foregoing remarks, whether the Court has jurisdiction to hear and determine the application of the Republic of Slovenia seeking a declaration that the Republic of Croatia has infringed provisions of EU law, the Court cannot confine itself to formally examining the wording of the complaints contained in the form of order sought in the application, but should analyse the substance of the complaints put forward by the Republic of Slovenia. ( 51 )

1. Analysis of the specific complaints of the Republic of Slovenia

114. The six complaints raised by the Republic of Slovenia can be broken down as follows: the first two allege infringements of the provisions of primary law (Article 2 and Article 4(3) TEU) and the other four allege infringements of secondary law, that is to say, obligations under the common fisheries policy established in Regulation No 1380/2013 (third complaint), under the control system established by Regulation No 1224/2009 and Implementing Regulation No 404/2011, both relating to the common fisheries policy (fourth complaint), under the Schengen Borders Code (fifth complaint) and, lastly, under the maritime spatial planning arrangements established by Directive 2014/89 (sixth complaint).

115. Those complaints can be divided into two categories, that is to say, complaints alleging infringement of primary law and complaints alleging infringement of secondary law. On examination, it can be seen that the arguments put forward in support of those complaints vary in structure depending on the category to which they belong.

116. The complaints alleging infringement of primary law seek to show that the Republic of Croatia’s failure to apply the arbitration agreement and to implement the arbitration award at issue constitutes an infringement of the value of the rule of law enshrined in Article 2 TEU and of the principle of sincere cooperation set out in Article 4(3) TEU.

117. More specifically, in its first complaint, alleging infringement of the value of the rule of law enshrined in Article 2 TEU, the Republic of Slovenia takes the view that, by unilaterally defaulting on the commitment, which it made during the process of accession to the European Union, to comply with the forthcoming arbitration award, the boundary delimited by the arbitration award at issue and the other obligations arising under that award, the Republic of Croatia is refusing to respect the value of the rule of law enshrined in that article and, accordingly, is infringing the principles of sincere cooperation and res judicata. In relation to the second complaint, alleging infringement of the principle of sincere cooperation enshrined in Article 4(3) TEU pursuant to which the European Union and the Member States, in full mutual respect, are to assist each other in carrying out tasks which flow from the Treaties, it must be noted that the Republic of Slovenia alleges two types of infringement by the Republic of Croatia, that is to say, jeopardising the attainment of the European Union’s objectives ( 52 ) and obstructing the implementation of EU law on Slovenian territory.

118. Its arguments relating to those two complaints indicate to me that the Republic of Slovenia is seeking to demonstrate that the Republic of Croatia’s failure to apply the arbitration agreement and to implement the arbitration award at issue constitutes an infringement of EU law, in particular of Article 2 TEU and the principles of sincere cooperation and res judicata.

119. In contrast, the complaints alleging infringement of the provisions of secondary law are based on the premiss that the boundary between the Republic of Croatia and the Republic of Slovenia has been determined by the arbitration award at issue, with the effect that the refusal to implement it constitutes an infringement of those provisions by the Republic of Croatia.

120. Given the structural difference between the complaints relating to primary law and those relating to secondary law, they should be examined in two parts.

2. Complaints alleging infringement of primary law

121. Having regard to my interim conclusion (point 112 of this Opinion), it is necessary to examine the relationship between, on the one hand, the arbitration agreement and the arbitration award at issue that was made under it and, on the other hand, EU law.

(a) The relationship between the arbitration agreement and the arbitration award at issue, on the one hand, and EU law, on the other

122. It needs to be emphasised that the arbitration agreement and, by extension, the arbitration award at issue made under that agreement do not correlate to any of the situations in which the European Union is bound by international law, as described in points 103 and 104 of this Opinion.

123. As regards the first scenario considered in point 104 of this Opinion, that is to say, where the European Union is bound by international agreements that it has concluded pursuant to the provisions of the Treaty, it should be noted that the arbitration award at issue was made by an international tribunal set up pursuant to a bilateral arbitration agreement. It is common ground that the European Union was not a party either to the arbitration agreement or in the arbitration proceedings in which that award was made. The European Union offered its good offices to the parties ( 53 ) and signed the agreement in question only as a ‘witness’. Under Article 4(a) and (b) of the arbitration agreement, the arbitral tribunal is to apply the rules and principles of international law as well as fairness and the principle of good neighbourly relations. In accordance with Article 8 of that agreement, the accession negotiations were not to affect the work of the arbitral tribunal, which was to continue in accordance with Article 9. The agreement, of which the European Union took note by a document of 25 September 2009, ( 54 ) therefore does not provide for the application of EU law. It is therefore apparent that the arbitration award at issue is a decision made by an arbitral tribunal set up pursuant to a bilateral arbitration agreement and applies, in particular, international law.

124. So far as concerns the second scenario envisaged in point 104 of this Opinion, that is to say, where the European Union is bound by an international convention if it has assumed the powers previously exercised by the Member States in the field to which the convention applies, it is clear that there was no transfer of powers from the Member States to the European Union in the field to which the arbitration agreement applies.

125. The third scenario referred to in point 104 of this Opinion, in which the European Union must respect the rules of customary international law, arises only where the European Union exercises its powers, which is not the situation in the present case, since the arbitration agreement and the arbitration award at issue are international instruments outside the European Union’s sphere of competence.

126. As regards whether the arbitration agreement or the arbitration award at issue may have been incorporated into EU law by the Act of Accession of the Republic of Croatia, it is apparent from the case file before the Court that one of the political conditions for the Republic of Croatia to accede to the European Union was the resolution of its boundary dispute with the Republic of Slovenia. ( 55 ) It is not contested that, at the time when the Accession Treaty was signed, the arbitration agreement had been entered into but the arbitration proceedings had not yet commenced. ( 56 ) However, nothing in the case file suggests that the political condition in question was embodied in any specific provisions of the Act of Accession or of the Accession Treaty. I am in fact of the view that the reference to the forthcoming arbitration award in Annex III to the Act of Accession, which is moreover the only reference in that act to the dispute concerning the boundary between the Republic of Croatia and the Republic of Slovenia, must be analysed as a statement that the rules regarding the common fisheries policy had to be modified in order to define the coastal waters of the two States at issue, for the purpose of applying the specific neighbourhood relations regime. Given the wording of that reference, ( 57 ) it cannot be construed as a legal obligation under EU law requiring the Republic of Croatia to resolve its dispute with the Republic of Slovenia in respect of their common boundary in accordance with the terms of the forthcoming arbitration award. ( 58 )

127. In the light of the foregoing, I do not believe that the European Union is bound by the arbitration agreement for the purposes of the case-law cited in point 103 of this Opinion, or by the award at issue for which that agreement provides, since those legal instruments are not within the scope ratione materiae of EU law.

128. In order to examine, in particular, whether the Court has jurisdiction to hear and determine the two complaints advanced by the applicant alleging infringement of primary law, it is appropriate, first, to examine the first complaint, alleging infringement of the value of the rule of law enshrined in Article 2 TEU (b), and secondly, to analyse the second complaint, alleging infringement of the principle of sincere cooperation enshrined in Article 4(3) TEU (c).

(b) The first complaint, alleging infringement of the value of the rule of law enshrined in Article 2 TEU

129. It should be noted at the outset that the Republic of Slovenia invokes the value of the rule of law both on its own and in combination with the principles of sincere cooperation and res judicata. In both instances, I believe that what has been said regarding the ancillary nature of allegations relating to purported infringements of EU law, set out in points 105 and 107 of this Opinion, applies when assessing this complaint.

130. In fact, although the form of order sought in the application formally refers to infringements of the value of the rule of law and of the principles of sincere cooperation and res judicata, the allegation itself relates to the purported infringement of international law, by the Republic of Croatia, resulting from failure to implement the arbitration award at issue. As emerges from point 127 of this Opinion, the European Union is bound neither by the arbitration agreement nor by the arbitration award at issue provided for by it; the matter of any infringements of EU law is therefore ancillary to that of delimitation of the land and maritime boundaries between the two Member States concerned.

131. Furthermore, as I have already indicated in point 126 of this Opinion, the attempt to link the commitments made during the Republic of Croatia’s accession to the European Union with those values and principles is not to my mind sufficient for those values and principles to serve as an independent basis for the action. The line of argument based on failure to fulfil commitments made during the accession process must therefore also be rejected, since those commitments are not legal obligations under EU law and cannot be relied upon for the purposes of Article 259 TFEU.

132. In any event and for the sake of completeness, in the first place, even assuming that the alleged infringements do fall within the scope of EU law, I would question whether a complaint based on the value of the rule of law enshrined in Article 2 TEU is admissible in an action for failure to fulfil obligations under Article 259 TFEU. The Court has recently had recourse to that value in numerous cases. ( 59 ) I note, however, that, in the case-law, the value of the rule of law has not been referred to on its own, but always with a provision that ‘gives concrete expression’ to it or of which it is ‘a specific manifestation’, ( 60 ) that is to say, Article 19 TEU. The link between the value of the rule of law and the jurisdiction of the European Union was in that way based on the fact that judicial review in the EU legal order is ensured not only by the Court of Justice but also by national courts and tribunals.

133. Admittedly, as regards implementation of Article 2 TEU, it is widely accepted that Article 7 TEU and the failure to fulfil obligations procedure are complementary ( 61 ) and that an action for failure to fulfil obligations can, in principle, address an infringement of Article 2 TEU. ( 62 ) Nevertheless, the fact remains that an action for failure to fulfil obligations is a remedy that is linked to the fields that fall within the scope of EU law – which, as set out in points 130 and 131 of this Opinion, the present case does not – and that requires specific legal obligations to be invoked. ( 63 ) Nonetheless, the Court can still have recourse to Article 2 TEU for interpretative purposes, in order to determine whether EU law has been infringed. My view is therefore that, even assuming that the Court has jurisdiction to examine the first complaint, alleging infringement of the rule of law, in the circumstances of the present case, that value cannot be relied upon on its own.

134. In the second place, in so far as the first complaint concerns the principle of good faith, which is manifested in EU law in the principle of sincere cooperation, and the principle of res judicata, since neither the arbitration agreement nor the arbitration award are either EU acts or international conventions binding on the European Union, ( 64 ) it is not sufficient to invoke those principles in conjunction with the value of the rule of law if a specific provision of EU law or a specific provision binding on the European Union is not invoked. No such tie exists where a complaint alleges failure to implement the arbitration award and to perform the arbitration agreement, which are bilateral instruments governed exclusively by international law.

135. My view is therefore that, in those circumstances, the Court does not have jurisdiction to hear and determine the complaint based on the value of the rule of law, because that complaint is ancillary to the question of the infringement of obligations under international law.

(c) The second complaint, alleging infringement of the principle of sincere cooperation enshrined in Article 4(3) TEU

136. First, the Republic of Slovenia contends in essence that, by refusing to fulfil its obligations under the arbitration award at issue, the Republic of Croatia is preventing it from fully exercising its sovereignty throughout its territory. It alleges that this conduct jeopardises attainment of the objectives of the European Union. ( 65 ) Secondly, the Republic of Slovenia alleges that the Republic of Croatia is preventing it from fulfilling its obligation to implement Directive 2008/56, Directive 92/43, Regulation No 1143/2014 and Directive 2000/60.

137. As already indicated in points 105 to 107 of this Opinion, the claims based on that principle are ancillary to resolution of the international dispute relating to the validity and implementation of the arbitration award at issue. It is to my mind particularly revealing in that respect how the Republic of Slovenia has worded its second complaint. It asserts that, ‘by unilaterally refusing to fulfil its obligations under the arbitration award [at issue]’, the Republic of Croatia has infringed the principle of sincere cooperation. ( 66 ) The Republic of Croatia is in that way preventing it from fully exercising its sovereignty throughout its mainland and maritime territory in compliance with the Treaties and provisions of secondary law. ( 67 )

138. In any event, the second complaint, alleging infringement of the principle of sincere cooperation enshrined in Article 4(3) TEU, should be rejected. According to my research, that principle has constituted an independent basis for obligations in cases where the European Union was party to a mixed agreement ( 68 ) or in the situation of fulfilment of the obligations under the EU Treaty and the FEU Treaty. ( 69 ) However, in the present case, the conduct at issue does not fall within either of those two situations. As can be seen from the foregoing analysis, in my view neither the arbitration agreement nor the arbitration award at issue constitute acts of EU law or international obligations binding on the European Union. ( 70 ) Performance of that agreement and implementation of that award are not obligations under the EU Treaty or the FEU Treaty. The only way in which the objectives of the European Union can be invoked is therefore by applying the framing of powers theory. According to that theory, exercise of the powers reserved to the Member States is restricted in the interests of attaining the objectives of the European Union. ( 71 ) Nevertheless, unlike the cases in which the Court has applied the framing of powers, ( 72 ) the present case concerns conduct, that is to say, a failure to implement the arbitration award, that has no link to EU provisions.

139. My view is therefore that, in those circumstances, the Court does not have jurisdiction to hear and determine the complaint alleging infringement of Article 4(3) TEU.

140. I therefore consider that the complaints alleging infringement of primary law must be rejected, since the Court does not have jurisdiction to examine a dispute that is primarily international, the infringement of EU law being merely ancillary. It is necessary to examine the complaints alleging infringements of provisions of secondary law.

3. Complaints based on secondary law

141. As is apparent from the general analysis of the complaints alleging infringements of secondary law advanced by the Republic of Slovenia, that party is relying, in support of those complaints, on the premiss that the boundary between the Republic of Croatia and the Republic of Slovenia has been determined by the arbitration award at issue made on the basis of the arbitration agreement. However, as I have observed several times in this Opinion, that agreement and the arbitration award at issue are not matters of EU law. Similarly, as I stated in the section relating to preliminary remarks, in particular points 109 to 112 of this Opinion, it can be seen from Article 52 TEU and Article 355 TFEU that the territorial scope of the Treaties is an objective fact predetermined by the Member States which the European Union has to accept. Against that background, it is necessary to examine whether the arbitration award at issue can be applied directly in the context of an action for failure to fulfil obligations.

(a) The arbitration award at issue is not self-executing and has not been implemented

142. On the one hand, I consider that, in principle, it would be possible to accept the Republic of Slovenia’s thesis that a decision of a recognised international court, such as the International Court of Justice (‘the ICJ’) or the PCA, constitutes a legal fact for this Court (res judicata). ( 73 ) In the present instance, in implementation of the arbitration agreement, ( 74 ) the proceedings before the arbitral tribunal at issue were conducted under the auspices of a permanent arbitral institution, the PCA, ( 75 ) which was appointed to act as Registry ( 76 ) by both the States in question. ( 77 )

143. On the other hand, to my mind, under EU law (Article 52 TEU and Article 355 TFEU) and, in particular, as regards the Member States’ responsibility for implementing that law, it is vital not only that the boundary between those States is legally and politically delimited, but that the delimitation is also implemented and operational. The Treaties do not give the European Union any power to determine where the respective territories belonging to two neighbouring States begin and end. Determining the extent and limits of territory concerns the sovereignty of each Member State, in accordance with the rules of public international law, as can be seen, mutatis mutandis, from Aktiebolaget NN. ( 78 )

144. It is to be noted, for that purpose, that, first, under the principle of conferral enshrined in Article 5(2) TEU, the European Union is to act only within the limits of the competences conferred upon it by the Member States in the Treaties to attain the objectives set out therein ( 79 ) and that, second, according to Article 4(1) TEU, any competence not conferred upon the European Union remains with the Member States. In my view, the present case concerns a competence reserved to the Member States. Accordingly, to enable EU law to be applied, the State boundaries must not only be determined under public international law, but must also be delimited in factual terms.

145. Even though the disputed boundary between the Republic of Croatia and the Republic of Slovenia has been determined by the arbitration award at issue, as is apparent from the documents before the Court, it should be noted that, in the present case, the Republic of Croatia fiercely contests the applicability and validity of the arbitration award at issue. Indeed, it cannot be overlooked that, by note verbale of 30 July 2015, the Republic of Croatia notified the Republic of Slovenia that it was terminating the arbitration agreement and that the procedure under Article 65 of the Vienna Convention was potentially applicable. ( 80 ) That notification was also given to the arbitral tribunal on 31 July 2015. Accordingly, from the time of that notification, the Republic of Croatia withdrew from the arbitration proceedings and no longer took part in them. In its written submissions and at the hearing, it argued that, by issuing the award at issue, the arbitral tribunal had exceeded its powers. ( 81 )

146. More generally, it should be noted that it is not unknown, in the history of international law and even today, ( 82 ) for one of the parties to arbitration proceedings not to recognise the validity of an award made by an arbitral tribunal or to refuse to implement that award. ( 83 ) Indeed, even though there is no binding mechanism for reviewing inter-State arbitration awards, a State that disputes such an award can bring a dispute concerning the validity of that award before the ICJ. ( 84 )

147. In that context, it is hardly surprising that the Republic of Croatia, in order to explain its reasons for not recognising the arbitration award at issue, relies on a claim that the arbitral tribunal exceeded its powers merely by issuing that award. ( 85 ) In practice, when a State disputes an inter-State arbitration award, that award represents in reality merely an attempt to resolve the dispute in question since, in public international law and given the fact that it can be regarded as inherently executory, there is no binding mechanism, independent of the sovereign will of the States, that ensures the implementation of inter-State arbitration awards. ( 86 )

148. Even supposing that, from an international law perspective, the partial award contains a legal assessment of the facts that are referred to in point 145 of this Opinion, ( 87 ) it is nevertheless true that the award has not, to date, been implemented in the relations between the Republic of Croatia and the Republic of Slovenia. I note in that respect that according to Article 7(3) of the arbitration agreement, ‘the parties shall take all necessary steps to implement the award, including by revising national legislation, as necessary, within six months after the adoption of the award.’ I concur to that effect with the argument of the Republic of Croatia, put forward at the hearing, that the arbitration award at issue is not self-executing, ( 88 ) which is to my mind tantamount to saying that it is not directly applicable. ( 89 )

149. I am therefore of the view that the arbitration award at issue has not been implemented in the relations between the Republic of Croatia and the Republic of Slovenia, and that therefore, from an EU law perspective, the boundary between those two Member States has not been established either within the meaning of Article 52 TEU and Article 355 TFEU or within the meaning of the Aktiebolaget NN ( 90 ) case-law, according to which it is for each Member State to determine the extent and limits of its territory, in accordance with the rules of public international law. Given that determining the boundaries between Member States is not a competence conferred on the European Union, for the purposes of Article 5(2) TEU, and does not fall within the scope ratione materiae of EU law, the matters at issue cannot be the subject matter of an action for failure to fulfil obligations under Article 259 TFEU.

150. In the light of the foregoing, the specific complaints based on secondary law advanced by the applicant in support of its action should be examined separately. It is necessary to analyse whether the Court of Justice has jurisdiction to hear and determine the complaints in support of the action based on, first, (section b) Article 5(2) of and Annex I to Regulation No 1380/2013 (third complaint) and, secondly, (section c) the control system, inspection and the implementation of the control system under Regulation No 1224/2009 and Implementing Regulation No 404/2011 (fourth complaint), Articles 4 and 17, in conjunction with Article 13, of the Schengen Borders Code (fifth complaint) and Articles 2(4) and 11(1) of Directive 2014/89 (sixth complaint).

(b) The third complaint, alleging infringement of Regulation No 1380/2013

151. By its third complaint, the Republic of Slovenia claims that, by failing to respect its territory, the Republic of Croatia has infringed EU law in relation to the common fisheries policy, specifically Article 5(2) of and Annex I to Regulation No 1380/2013. ( 91 )

152. I note at the outset that, unlike other acts of secondary law invoked by the Republic of Slovenia, Regulation No 1380/2013 contains an explicit reference to the forthcoming arbitration award. According to the footnotes to points 8 and 10, entitled ‘Coastal waters of Croatia’ (point 8) and ‘Coastal waters of Slovenia’ (point 10), of Annex I to Regulation No 1380/2013, ‘the above mentioned regime shall apply from the full implementation of the arbitration award …’. Since Regulation No 1380/2013 is an EU legislative act within the meaning of Article 297 TFEU, the Court clearly has jurisdiction to decide whether the requirements for that regulation to apply are satisfied, that is to say, whether the specific neighbourhood relations regime under Article 5(2) of that regulation, in the light of the precise indications in Annex I, applies.

153. However, to the extent that, by that third complaint, alleging infringement of Article 5(2) of and Annex I to Regulation No 1380/2013, ( 92 ) the Republic of Slovenia is seeking a declaration that the Republic of Croatia has infringed the regime established in that article, my view is that the Court does not have jurisdiction to examine that complaint.

154. It should be observed in that respect that Article 5(1) of Regulation No 1380/2013 provides for equal access to waters and resources in all EU waters, with the exception of those referred to, in particular, in Article 5(2). Article 5(2) authorises the Member States, in the waters up to 12 nautical miles from baselines under their sovereignty or jurisdiction, until 31 December 2022, to restrict fishing to fishing vessels that traditionally fish in those waters from ports on the adjacent coast, without prejudice to the arrangements for EU fishing vessels flying the flag of other Member States under existing neighbourhood relations between Member States and the arrangements contained in Annex I, fixing for each Member State the geographical zones within the coastal bands of other Member States where fishing activities are pursued and the species concerned. Annex I to that regulation defines the conditions of access to coastal bands within the meaning of Article 5(2) of the regulation. According to the footnotes to points 8 and 10 of Annex I to Regulation No 1380/2013, entitled ‘Coastal waters of Croatia’ (point 8) and ‘Coastal waters of Slovenia’ (point 10), ‘the above mentioned regime shall apply from the full implementation of the arbitration award …’. In the absence of further clarification of that wording, it is necessary to interpret it in order to understand the scope of that reference to the forthcoming arbitration award.

155. The Court has already stated that the expression ‘the above mentioned regime’ referred to certain specific arrangements giving EU fishing vessels flying the flags of other Member States the right to fish in the 12-mile zones under pre-existing neighbourhood relations between Member States. ( 93 ) That expression should therefore be understood as referring to the specific reciprocal access regime ‘applicable to Union fishing vessels flying the flags of other Member States under pre-existing neighbourhood relations between Member States’ (‘the specific regime under neighbourhood relations’).

156. As regards the expression ‘from the full implementation of the arbitration award’ in points 8 and 10 of Annex I to Regulation No 1380/2013, which reflect the contents of the Act of Accession, ( 94 ) it follows that the final award is an act that dictates the application ratione temporis of the specific regime under neighbourhood relations, the arrangements for which are laid down in Annex I to the regulation. Accordingly, that regime cannot come into force before ‘full implementation’ of the future arbitration award by the Republic of Croatia and the Republic of Slovenia. In other words, the purpose of points 8 and 10 of Annex I is to suspend applicability of that regime pending resolution of the dispute concerning the contested boundaries between those two States. In the present instance, as the Republic of Croatia confirmed at the hearing, the arbitration award at issue has not been implemented, because that Member State believes that it has validly terminated the arbitration agreement ( 95 ) and refuses to recognise the arbitration award at issue made under it. I am therefore of the view that, so far as the Croatian and Slovenian coastal waters are concerned, the aforementioned specific regime under neighbourhood relations does not apply ratione temporis. Given that the applicant alleges that the Republic of Croatia has infringed the specific regime under neighbourhood relations, established in Article 5(2) of Regulation No 1380/2013, which applied neither during the alleged failures to fulfil obligations nor during these proceedings, because the arbitration award at issue has not been implemented, in my view the Court does not have jurisdiction to examine the third complaint.

(c) The fourth to sixth complaints in support of the action

157. For the fourth to sixth complaints advanced by the Republic of Slovenia, it relies on provisions relating to the control system established by Regulation No 1224/2009 and Implementing Regulation No 404/2011 (fourth complaint), Articles 4 and 17, in conjunction with Article 13, of the Schengen Borders Code (fifth complaint) and Articles 2(4) and 11(1) of Directive 2014/89 (sixth complaint).

158. First, in respect of the fourth complaint, alleging infringement of the provisions in Regulation No 1224/2009 and Implementing Regulation No 404/2011, the conduct criticised is the fact that ‘Croatian police patrol boats, without authorisation from the Republic of Slovenia, are accompanying Croatian fishing vessels when they fish in Slovenian waters, thereby preventing Slovenian fishing inspectors from carrying out controls’. The applicant adds that ‘the Croatian authorities are imposing fines on Slovenian fishing vessels for unlawful boundary crossing and illegal fishing when they fish in Slovenian waters which [the Republic of] Croatia claims for itself’ and that the Republic of Croatia ‘is not sending [the Republic of] Slovenia the data regarding the activities of Croatian vessels in Slovenian waters, as is required by those two regulations’. It concludes that, by so doing, the Republic of Croatia ‘is not permitting the [Republic of Slovenia] to carry out controls in waters under its sovereignty and jurisdiction and is not respecting the Republic of Slovenia’s exclusive jurisdiction over its territorial waters as a coastal State’. ( 96 )

159. Secondly, in relation to the fifth complaint, alleging infringement of the Schengen Borders Code, I note that, according to the Republic of Slovenia, the Republic of Croatia ‘does not recognise the boundaries established by the arbitration award as a common boundary with [the Republic of] Slovenia, is not cooperating with [that State] to protect that “external border” and is not in a position to guarantee adequate protection of that border’, thereby contravening Articles 4, 13 and 17 of that code.

160. Thirdly, as regards the sixth complaint, based on an alleged infringement of Directive 2014/89, it should be noted that the Republic of Slovenia relies directly on the failure to implement the arbitration award at issue delimiting territorial waters for the purposes of Article 2(4) of that directive. According to the applicant, the Republic of Croatia includes Slovenian waters in its maritime spatial planning and, consequently, prevents harmonisation with the maps of the Republic of Slovenia

161. It should be stated in that respect that the Republic of Slovenia’s arguments relating to the alleged infringement of secondary law are based on the premiss that the disputed boundary has in fact been determined. That statement is corroborated by the events invoked by the Republic of Slovenia in support of its claims, from which it is apparent that those events would not have occurred if there had been an operational boundary between the Republic of Croatia and the Republic of Slovenia. However, as can be seen from points 145 to 150 of this Opinion, in my view that is not the case, because the arbitration award at issue has never been implemented. This means that the Republic of Slovenia is seeking, by implication, to have the arbitration award at issue implemented. However, such an application for implementation falls outside the European Union’s sphere of competence. If the Court had to rule on the fourth to sixth complaint worded in that way, it would find itself having to rule on the issue of the disputed boundary whereas, as can be seen from points 143 and 144 of this Opinion, that competence lies with the Member States (see point 110 of this Opinion). The alleged infringements of secondary law are therefore inherently ancillary to the question of determining, on the basis of the facts, the boundary between the Republic of Croatia and the Republic of Slovenia. I therefore propose that the Court should find that it does not have jurisdiction to hear and determine the fourth to sixth complaints put forward by the Republic of Slovenia in support of its action.

162. In the light of the foregoing, I propose that the Court should find that it does not have jurisdiction to hear and determine the complaint based on primary law and on secondary law and, therefore, to rule on the present action in its entirety.

163. It is therefore unnecessary to examine further the matter of the Republic of Croatia’s grounds of challenge relating to the inadmissibility of the application.

D. Summary of the analysis

164. Although the complaint alleging failures to fulfil obligations advanced by the Republic of Slovenia might, at first sight, appear to be complaint relating to EU law for the purposes of Article 259 TFEU, after in-depth analysis I have reached the conclusion that any finding that the Republic of Croatia has committed the infringements alleged would be based on the premiss that the boundary between the Republic of Croatia and the Republic of Slovenia has been determined. Determining that boundary is, by its very nature, a matter falling within public international law, as is confirmed by analysing the arbitration agreement and the arbitration award at issue, which cannot be regarded as acts of EU law. Questions concerning the validity, interpretation and implementation of those two international legal instruments cannot be the subject matter of a failure to fulfil obligations under Article 259 TFEU. Furthermore, I find that the arbitration award at issue has not been implemented in the relations between those two Member States, and is moreover not self-executing. It follows that, under EU law, the disputed boundary has not been established between the Republic of Croatia and the Republic of Slovenia for the purposes of Article 52 TEU and Article 355 TFEU. Since the alleged failures to fulfil obligations advanced by the Republic of Slovenia relate to the disputed boundary between those two Member States, those allegations must be found to be merely ancillary to resolution of the international dispute, which does not fall within EU law and over which the Court does not have jurisdiction.

165. Ultimately, I am bound to say that it is regrettable that the boundary dispute could not be definitively resolved even once the arbitration award at issue was made. Nevertheless, I am persuaded that the resolution of that dispute must be a political one.

VII. Costs

166. Under Article 138(1) of the Rules of Procedure of the Court of Justice, the unsuccessful party is to be ordered to pay the costs if they have been applied for in the successful party’s pleadings.

167. It is apparent from the grounds set out above that the Republic of Slovenia is the unsuccessful party in the present case and must bear its own costs and pay those of the Republic of Croatia.

VIII. Conclusion

168. In the light of the foregoing, I propose that the Court should: – remove from the case file the opinion of the European Commission’s Legal Service contained in Annex C.2 to the Republic of Slovenia’s response to the objection of inadmissibility; – declare that the Court of Justice of the European Union does not have jurisdiction to hear and determine the present action; – order the Republic of Slovenia to bear its own costs and pay those of the Republic of Croatia.

( 1 ) Original language: French.

( 2 ) Formerly Article 170 of the EEC Treaty and Article 227 of the EC Treaty. On actions under those articles, see, in particular, judgments of 4 October 1979, France v United Kingdom (141/78, EU:C:1979:225); of 16 May 2000, Belgium v Spain (C‑388/95, EU:C:2000:244); of 12 September 2006, Spain v United Kingdom (C‑145/04, EU:C:2006:543); of 16 October 2012, Hungary v Slovakia (C‑364/10, EU:C:2012:630); and of 18 June 2019, Austria v Germany (C‑591/17, EU:C:2019:504).

( 3 ) Signed in San Francisco on 26 June 1945.

( 4 ) OJ 2012 L 112, p. 10.

( 5 ) UN Treaty Series, vol. 1155, p. 331.

( 6 ) OJ 2012 L 112, p. 21.

( 7 ) Council Regulation (EC) No 2371/2002 of 20 December 2002 on the conservation and sustainable exploitation of fisheries resources under the Common Fisheries Policy (OJ 2002 L 358, p. 59).

( 8 ) Regulation amending Council Regulations (EC) No 1954/2003 and (EC) No 1224/2009 and repealing Council Regulations (EC) No 2371/2002 and (EC) No 639/2004 and Council Decision 2004/585/EC (OJ 2013 L 354, p. 22).

( 9 ) Regulation amending Regulations (EC) No 847/96, (EC) No 2371/2002, (EC) No 811/2004, (EC) No 768/2005, (EC) No 2115/2005, (EC) No 2166/2005, (EC) No 388/2006, (EC) No 509/2007, (EC) No 676/2007, (EC) No 1098/2007, (EC) No 1300/2008, (EC) No 1342/2008 and repealing Regulations (EEC) No 2847/93, (EC) No 1627/94 and (EC) No 1966/2006 (OJ 2009 L 343, p. 1).

( 10 ) OJ 2011 L 112, p. 1.

( 11 ) OJ 2016 L 77, p. 1.

( 12 ) OJ 2014 L 257, p. 135.

( 13 ) Paragraph 17 of the partial award made by the arbitral tribunal on 30 June 2016 (‘the partial award’).

( 14 ) Paragraph 18 of the partial award.

( 15 ) The PCA has 122 contracting parties which have acceded to one or both of the PCA’s founding conventions. So far as concerns the present case, the Republic of Slovenia acceded to both conventions, on 1 October 1996 and 29 March 2004 respectively. The Republic of Croa