1  Following intense deliberations extending over a period of eight years, the United Nations Convention on the Law of the Sea (ʻUNCLOSʼ) was adopted on 10 December 1982. This multilateral treaty was concluded with the purpose to ʻsettle, in a spirit of mutual understanding and cooperation, all issues relating to the law of the seaʼ (Preamble). The UNCLOS stands out, inter alia, for the compulsory system of peaceful settlement of disputes concerning the interpretation and application of the Convention established by its Part XV. Together with Annex VI UNCLOS which constitutes the Statute of the ITLOS (‘Statute’), this Part serves as the legal basis for the creation of the International Tribunal for the Law of the Sea (ITLOS). According to Article 287 (1) UNCLOS, when signing, ratifying, or acceding to this Convention or at any time thereafter, States are free to choose, by means of a written declaration, one or more of several means for the settlement of disputes concerning the interpretation or application of the Convention, one of which being the ITLOS. If and to the extent to which a State party has not submitted such a declaration, Article 287 (3) UNCLOS assumes the jurisdiction of an arbitral tribunal established in accordance with Annex VII of the Convention (Annex VII Arbitration: United Nations Convention on the Law of the Sea (UNCLOS)). The jurisdiction of the ITLOS is subject to special rules, however, as (i) Article 287 (2) UNCLOS prescribes an obligation to ʻaccept the jurisdiction of the Seabed Disputes Chamber of the International Tribunal for the Law of the Sea to the extent and in the manner provided for in Part XI, section 5, (ii) Article 290(5) UNCLOS allocates to the ITLOS, pending the constitution of an arbitral tribunal to which a dispute is being submitted, a subsidiary competence to prescribe, modify or revoke provisional measures, and (iii) Article 292 UNCLOS envisages the subsidiary jurisdiction of the ITLOS for cases concerning the prompt release of vessels and crews.

2  As far as the competence to give advisory opinions is concerned, the UNCLOS prescribes in its Article 191 that the Seabed Disputes Chamber: International Tribunal for the Law of the Sea (ITLOS) (International Courts and Tribunals, Chambers) ʻshall give advisory opinions at the request of the Assembly or the Council on legal questions arising within the scope of their activities.ʼ However, in contrast to Article 96 of the United Nations Charter (ʻUN Charterʼ), which entrusts the International Court of Justice (ICJ) with the competence ʻto give an advisory opinionʼ on the request of the General Assembly, the Security Council or, provided that they were correspondingly authorized by the General Assembly, other organs of the UN and specialized agencies, neither Part XV UNCLOS nor the Statute establishes an explicit competence of the ITLOS as a full court to render advisory opinions on legal questions arising in the context of the interpretation and application of the Convention. That said, Article 138(1) of the Rules of the Tribunal (ʻRulesʼ) specifies that ʻ[t]he Tribunal may give an advisory opinion on a legal question if an international agreement related to the purposes of the Convention specifically provides for the submission to the Tribunal of a request for such an opinion.ʼ

3  As stated, the UNCLOS allocates advisory jurisdiction in express terms only to the Seabed Disputes Chamber of the ITLOS, but not to the Tribunal as such. According to Article 159 (10) and Article 191 UNCLOS, the advisory function of the Chamber concerns legal questions submitted by the Assembly or by the Council. Articles 187 to 190 UNCLOS also confer contentious jurisdiction (Judgment: International Tribunal for the Law of the Sea (ITLOS)) to the Chamber concerning the settlement of certain disputes that have arisen with respect to activities in the Area. The Seabed Disputes Chamber is ʻa separate judicial body within the Tribunal entrusted, through its advisory and contentious jurisdiction, with the exclusive function of interpreting Part XI of the Convention and the relevant annexes and regulations that are the legal basis for the organization and management of activities in the Areaʼ (Responsibilities and Obligations of States Sponsoring Persons and Entities with respect to Activities in the Area, Advisory Opinion, 2011, para 25). Article 186 UNCLOS clarifies that ʻ[t]he establishment of the Seabed Disputes Chamber and the manner in which it shall exercise its jurisdiction shall be governed by the provisions of this section, of Part XV and of Annex VI.ʼ According to Article 35 of the Statute, it is composed of 11 members, selected by a majority of the elected members of the Tribunal from among them.

4  The main purpose of the advisory jurisdiction of the Seabed Disputes Chamber has been described by the Chamber as being based on the fact that the International Seabed Authority (ISA), the international organization established by the UNCLOS in order to ʻorganize and control activities in the Areaʼ (Article 157 (1) UNCLOS), may, ʻin order to exercise its functions properly in accordance with the Convention, […] require the assistance of an independent and impartial judicial bodyʼ (Responsibilities and Obligations of States Sponsoring Persons and Entities with respect to Activities in the Area, Advisory Opinion, 2011, para 26). This is why only the two principal organs of the International Seabed Authority (ʻAuthorityʼ, ʻISAʼ), namely the Assembly on the one hand and the Council on the other, are entitled to request an advisory opinion of the Seabed Disputes Chamber. Advisory opinions given upon the request of the Assembly on the basis of Article 159 (10) UNCLOS serve to assist it in its decision-making progress (Responsibilities and Obligations of States Sponsoring Persons and Entities with respect to Activities in the Area, Advisory Opinion, 2011, para 27). The Chamberʼs advisory jurisdiction under Article 191 UNCLOS concerns legal questions arising within the scope of both the Assembly and the Council’s activities and shall be given as a matter of urgency. Thus, by rendering advisory opinions, the Chamber contributes to the lawful implementation and development of the regime of the Area enshrined in Part XI UNCLOS.

5  Article 191 UNCLOS sets out the conditions under which the Seabed Disputes Chamber is entitled to exercise its advisory jurisdiction. These conditions are (1) that there is a request of the Assembly or the Council, (2) that the request concerns legal questions, (3) and that these questions have arisen within the scope of activities of the Assembly or Council (see also Responsibilities and Obligations of States Sponsoring Persons and Entities with respect to Activities in the Area, Advisory Opinion, 2011, para 32). The first condition is met if the Assembly or Council has adopted a decision in line with the procedural requirements laid down in the UNCLOS, the 1994 Agreement relating to the Implementation of Part XI of the United Nations Convention on the Law of the Sea (ʻ1994 Implementation Agreementʼ) and the Rules of Procedure of the two organs, by which the Seabed Disputes Chamber is requested to give an advisory opinion. Section 3 para 2 of the Annex to the 1994 Implementation Agreement clarifies that ʻ[a]s a general rule, decision-making in the organs of the Authority should be by consensus.ʼ According to Article 2(1) of the 1994 Implementation Agreement, its provisions and those of Part XI UNCLOS must be interpreted and applied together as a single instrument, but in case of inconsistencies the 1994 Implementation Agreement enjoys priority over Part XI UNCLOS.

6  Article 159 (10) UNCLOS refers to the case of a request of an advisory opinion on the conformity with the UNCLOS of a proposal before the Assembly on any matter. As correctly stated by one commentator, this provision establishes a special procedural rule rather than a separate legal basis for a competence of the Assembly to request advisory opinions (Schatz, 2017, para 16), inasmuch as ‘at least one fourth of the members of the Assembly’ are required to request the Assembly to ask the Chamber for an advisory opinion. Its wording (ʻshall requestʼ) demonstrates that the Assembly is bound to submit the proposal to the Chamber, which is why it must postpone voting on the said matter until the opinion has been given. In the absence of a reference to the requesting members being present and voting, Article 159 (10) UNCLOS has been interpreted as enabling members of the Authority who are not present at a session of the Assembly to take part in a request for an advisory opinion (Schatz, 2017, para 15).

7  As far as the second condition is concerned, the questions submitted to the Seabed Disputes Chamber ought to be of legal, and not merely political, nature. In its advisory opinion concerning responsibilities and obligations of States sponsoring persons and entities with respect to activities in the Area, the Chamber relied on the relevant case-law of the ICJ, according to which the questions ought to be framed in terms of law, raise problems of international law, and, by their very nature, be susceptible of a reply based on law (Responsibilities and Obligations of States Sponsoring Persons and Entities with respect to Activities in the Area, Advisory Opinion, 2011, para 39). The special procedural rule codified in Article 159 (10) UNCLOS is applicable to only one category of legal questions, namely the issue of whether a proposal before the Assembly is in conformity with the UNCLOS.

8  Finally, Article 191 UNCLOS demands as a third condition that the questions concerned have arisen within the scope of activities of the Assembly or Council. Whether or not the ʻscope of activitiesʼ of the Assembly or the Council is affected ought to be evaluated on the basis of an assessment of whether the questions are related to the powers and functions of these organs (Responsibilities and Obligations of States Sponsoring Persons and Entities with respect to Activities in the Area, Advisory Opinion, 2011, para 41; see also Burke, 2017, para 8). In order to establish its advisory jurisdiction, the Seabed Disputes Chamber is thus required to interpret the scope of the relevant provisions. In this respect, while the powers and functions of the Council are set out in Articles 161 to 165 UNCLOS, in particular Article 162 UNCLOS, read together with the Annex to the 1994 Implementation Agreement (Responsibilities and Obligations of States Sponsoring Persons and Entities with respect to Activities in the Area, Advisory Opinion, 2011, paras 42 ff), those of the Assembly are codified in Articles 159 and 160 UNCLOS.

9  In the case concerning responsibilities and obligations of States sponsoring persons and entities with respect to activities in the Area before the Seabed Disputes Chamber, some participants in the proceedings had argued that the Chamber had no discretion in deciding whether or not to give the requested opinion. Thus, once the conditions for the exercise of its advisory jurisdiction codified in Article 191 UNCLOS are fulfilled, the Chamber would no longer be entitled to decline the request for an advisory opinion. The Seabed Disputes Chamber took account of the issue but refrained from deciding it, as it deemed it appropriate to give the requested opinion (Responsibilities and Obligations of States Sponsoring Persons and Entities with respect to Activities in the Area, Advisory Opinion, 2011, paras 47 ff). Indeed, in contrast to the wording of Article 65 (1) of the Statute of the ICJ (ʻICJ Statuteʼ), Article 191 UNCLOS states that the Chamber ʻshall giveʼ advisory opinions, a phrase that is generally understood as establishing a legal obligation (see Nandan/Lodge/Rosenne, 2002, 641; Chandrasekhara Rao and Gautier, 2018, para 3.208). Also in light of the purpose of the advisory jurisdiction of the Seabed Disputes Chamber to contribute to the lawful implementation and development of the regime of the Area enshrined in Part XI UNCLOS, it is submitted that the better reasons militate against the existence of a discretion of the Chamber in deciding whether or not to give the requested opinions.

10  The procedural rules applicable to advisory proceedings before the Seabed Disputes Chamber are codified in Article 40 (2) of the Statute in conjunction with Articles 130 to 137 of the Rules (see Chandrasekhara Rao and Gautier, 2018, para 4.308 ff). Article 40 (2) of the Statute seems to grant to the Chamber a considerable scope of discretion (ʻto the extent to which it recognizes them to be applicableʼ) as to whether it intends to apply other provisions of the Statute. This has been explained by referring to the fact that the provisions of section 3 of the Statute reflect the primarily contentious jurisdiction of the Tribunal (Vrancken, 2017, para 5). Notwithstanding this, the Chamber cannot be considered as being free to decide about the procedural rules governing advisory procedures. Rather, it must arguably apply the provisions of the Statute unless, as a matter of logic, their application does not lead to meaningful results in the context of advisory proceedings.

11  Article 293 (1) UNCLOS and Article 38 of the Statute prescribe the law to be applied by the Chamber (see also Responsibilities and Obligations of States Sponsoring Persons and Entities with respect to Activities in the Area, Advisory Opinion, 2011, paras 50 ff). Naturally, the primary source to be applied by the Chamber are the provisions of the UNCLOS themselves. As far as the reference in Article 293 (1) to ʻother rules of international law not incompatible with this Conventionʼ is concerned, it is important to note that the provisions on the applicable law must not be used by the Chamber to indirectly expand the scope of its advisory jurisdiction (Tzeng, 2016, 247 ff). On the other hand, there is no doubt that the Chamber must also apply the provisions of the 1994 Implementation Agreement, taking into account that this Agreement and the provisions contained in Part XI UNCLOS ought to be interpreted and applied together as a single instrument according to Article 2 (1) of the 1994 Implementation Agreement (Responsibilities and Obligations of States Sponsoring Persons and Entities with respect to Activities in the Area, Advisory Opinion, 2011, para 54). Article 38 of the Statute clarifies that in addition to what is stated in Article 293 UNCLOS, the Chamber is under an obligation (ʻshallʼ) to apply ʻ(a) the rules, regulations and procedures of the Authority adopted in accordance with this Convention; and (b) the terms of contracts concerning activities in the Area in matters relating to those contracts.ʼ

12  The UNCLOS is silent on the legal effects of advisory opinions rendered by the Seabed Disputes Chamber. According to Article 39 of the Statute, ʻdecisions of the Chamber shall be enforceableʼ, and the Chamber, when exercising its functions relating to advisory opinions, ʻshall be guided by the provisions of this Annex relating to procedure before the Tribunal to the extent to which it recognizes them to be applicableʼ (Article 40 (2) of the Statute). Notwithstanding this, the correct view is that advisory opinions of the Seabed Disputes Chamber are not legally binding and, thus, not enforceable (García-Revillo, 2015, 306; Ndiaye, 2010, paras 35, 52; Tanaka, 2018, 265). While it is not impossible that an advisory opinion takes binding legal effect, this will, taking into account the limited legal effects assigned to advisory opinions of international courts and tribunals in general (see para 31 below), only be the case if the underlying treaty expressly assigns binding force to it (Tanaka, 2018, 170–1). Such effect has not been assigned by the UNCLOS to advisory opinions of the Seabed Disputes Chamber. That said, Article 159 (10) UNCLOS provides evidence for the existence of a limited, and indirect, legal effect: if the Seabed Disputes Chamber has been requested by the Assembly to give an advisory opinion on a matter covered by that provision, the Assembly shall defer from voting on the pertinent proposal pending receipt of the advisory opinion (García-Revillo, 2015, 307). Beyond that, the effects of advisory opinions rendered by the Seabed Disputes Chamber are not categorically different than those of opinions submitted by other courts or tribunals, including the ITLOS as a full court (see below para 31). The cautious view taken here is supported by the careful vocabulary used by the Seabed Disputes Chamber in its 2011 Advisory Opinion: The Chamber was ‘mindful of the fact that by answering the questions it will assist the Council in the performance of its activities and contribute to the implementation of the Convention’s regime’ (Responsibilities and Obligations of States Sponsoring Persons and Entities with respect to Activities in the Area, Advisory Opinion, 2011, para 30). Perhaps more importantly, while it rendered ‘decisions’ on its jurisdiction and on the question whether it should respond to the request to give an advisory opinion, it merely ‘replied’ to the questions submitted to it by the Council of the ISA. At the same time, it is not easy to determine the specific impact that the advisory opinion has had in practice. It is submitted that section 7 of Annex X (‘Standard clauses for exploitation contract’) to the Draft Regulations on Exploitation of Mineral Resources in the Area (ISBA, 2018), which addresses the issue of liability and responsibility, reflects the distribution of responsibilities for deep seabed mining activities between the contractor, the Authority and the sponsoring State which the Seabed Disputes Chamber deduced from Article 22 Annex III UNCLOS in its Advisory Opinion (Responsibilities and Obligations of States Sponsoring Persons and Entities with respect to Activities in the Area, Advisory Opinion, 2011, paras 199–201).

13  Article 138 (1) of the Rules envisages that the ITLOS may give an advisory opinion on any other legal question ʻif an international agreement related to the purposes of the Convention specifically provides for the submission to the Tribunal of a request for such an opinion.ʼ It has convincingly been argued by one commentator that this provision would not apply to ʻrequests for an advisory opinion on matters covered by or related to the activities of the international seabed regime, since, under the Convention, the Seabed Disputes Chamber enjoys exclusive jurisdiction over such mattersʼ (Jesus, 2006, 394). Thus, Article 138 of the Rules only applies to requests for an advisory opinion on legal questions that are not related to Part XI UNCLOS.

14  Notwithstanding the fact that the Tribunal has the power to establish its own Rules, Article 138 (1) of the Rules would be problematic if the UNCLOS itself, including its Statute, did not establish a competence of the ITLOS to render advisory opinions as a full court. While according to Article 16 of the Statute, the Tribunal is under an obligation to ʻframe rules for carrying out its functionsʼ and in particular to ʻlay down rules of procedureʼ, this does not entitle it to confer upon itself, by adopting the Rules, powers broader than those envisaged by the UNCLOS (Ruys and Soete, 2016, 159). Neither does the fact that the States parties to the UNCLOS have allocated to the ITLOS the ʻcompétence de la compétenceʼ (see Article 288 (4) UNCLOS), and that it is thus under a legal obligation to ascertain its own competence, imply that the Tribunal would be free to determine, or expand respectively, its powers beyond the scope envisaged by its constituent instrument. Thus, the question arises whether the UNCLOS, being the constituent instrument for the jurisdiction of the Tribunal, can be interpreted as providing a legal basis for an advisory jurisdiction. It is interesting to note that a parallel can be drawn here with a view to the question whether the Tribunal, when having exercised its contentious jurisdiction, has the power to revise its judgments: While the Convention, with the exception of the issue of provisional measures (see Article 25 (2) of the Statute), and in contrast to the ICJ Statute (see Article 61), is silent on this matter, Article 127 of the Rules does indeed envisage such a power.

15  Two provisions have been identified as being potentially relevant in this respect (You, 2008, 361). The first one is Article 288 (2) UNCLOS which accepts that the jurisdiction of the ITLOS (or any other court or tribunal referred to in Article 287 UNCLOS) may be derived from another international agreement related to the purposes of the Convention. However, this rule only applies in respect of disputes concerning the interpretation and application of the agreement concerned. In contrast, Article 21 of the Statute extends the jurisdiction of the Tribunal to ʻall matters specifically provided for in any other agreement which confers jurisdiction on the Tribunal.ʼ By referring to ʻmattersʼ and not only to ʻdisputesʼ, this provision could possibly be regarded as broadening the competence of the ITLOS compared to what is envisaged by Part XV UNCLOS.

16  The potential discrepancy between Article 288 (2) UNCLOS on the one hand and Article 21 of the Statute on the other has been a matter of scholarly debate, in particular in relation to the issue of a potential competence of the Tribunal to render advisory opinions as a full court (Rao, 2002, 208–9; Ndiaye, 2010, paras 58 ff; You, 2008, 360 ff). As a matter of principle, Article 318 UNCLOS clarifies that the ʻAnnexes form an integral part of this Convention and, unless expressly provided otherwise, a reference to this Convention or to one of its Parts includes a reference to the Annexes relating thereto.ʼ There is thus no hierarchical relationship between the Convention itself and its Annexes. Rather, as can also be demonstrated by reference to Article 1 (1) of the Statute (ʻshall function in accordance with the provisions of this Convention and this Statuteʼ), the two sets of provisions ought to be regarded as complementing each other (Lekkas and Staker, 2017, para 12).

17  As far as the specific competence to give advisory opinions is concerned, however, it has been observed by commentators that ʻan advisory function for the Tribunal was not even proposed during the Third Conference on the Law of the Sea […]ʼ (Lekkas and Staker, 2017, para 16; see also García-Revillo, 2015, 311), which is why it appears questionable whether Article 21 of the Statute can really be understood in a way as to establish an advisory jurisdiction of the Tribunal as a full court. It is perhaps also not without relevance that Article 138 of the Rules did not appear in any of the drafts of the Rules prepared by the ITLOS Preparatory Commission. Against this background, following the request submitted by the Sub-Regional Fisheries Commission (ʻSRFCʼ) to the ITLOS to give an advisory opinion on the existence and scope of rights and obligations of flag States and coastal States in relation to illegal, unreported and unregulated fishing activities (‘IUU fishing’), several States argued that none of the three types of cases mentioned in Article 21 of the Statute would be open to an advisory competence of the full bench of the Tribunal, and that the ITLOS had thus exceeded its regulative competences under Article 16 of the Statute when adopting Article 138 of the Rules (see, eg, Written Statement of the Peopleʼs Republic of China of 26 November 2013, paras 32 ff; Written Statement of Australia, 28 November 2013, paras 26, 34 ff; Written Statement of the United Kingdom, 28 November 2013, para 18). In contrast, other States took the view that the words ʻall mattersʼ used by Article 21 of the Statute would indeed include requests for advisory opinions (eg Written Statement by the Federal Republic of Germany, 18 November 2013, para 8 see also Chandrasekhara Rao and Gautier, 2018, para 3.210).

18  Perhaps unsurprisingly, the ITLOS, when assessing whether it had jurisdiction to give the requested advisory opinion, held that ʻarticle 21 of the Statute should not be considered as subordinate to article 288 of the Convention. It stands on its own footing and should not be read as being subject to article 288 of the Conventionʼ (SRFC, Advisory Opinion, 2015, para 52). This statement is in line with Article 318 UNCLOS, according to which the ʻAnnexes form an integral part of this Convention […].ʼ The Tribunal furthermore took the view that ʻ[t]he words all “matters” (“toutes les fois que cela” in French) should not be interpreted as covering only “disputes”, for, if that were to be the case, Article 21 of the Statute would simply have used the word “disputes”ʼ (SRFC, Advisory Opinion, 2015, para 56), but that it would have to mean something more than only disputes. According to the Tribunal, this ʻsomething more must include advisory opinions, if specifically provided for in “any other agreement which confers jurisdiction on the Tribunal”ʼ (SRFC, Advisory Opinion, 2015, para 56). The ITLOS rejected the argument that the expression ʻall mattersʼ codified in Article 21 of the Statute should have the same narrow meaning as it has under the Statutes of the Permanent Court of International Justice (PCIJ) and the ICJ, taking into account the alleged differences in contexts, objects and purposes, subsequent practices and negotiating histories between these Statutes on the one hand and the UNCLOS on the other (SRFC, Advisory Opinion, 2015, para 57). The advisory jurisdiction of the Tribunal would be established neither by Article 138 of the Rules nor by Article 21 of the Statute alone, but by the specific ʻother agreementʼ referred to by these provisions (SRFC, Advisory Opinion, 2015, paras 58–9).

19  Several commentators as well as States parties to the UNCLOS (Report of the Twenty-fifth Meeting of States Parties, para 23) have expressed their disagreement with the interpretation of Article 21 of the Statute submitted by the Tribunal. Aside from criticizing the fact that the ITLOS did not sufficiently specify the reasons for its conclusion (Gao, 2015, para 9; Ruys and Soete, 2016, 161; see also SRFC, Advisory Opinion (Separate Opinion of Judge Lucky), 2015, para 1), the argument has been presented that the ITLOS ignored that Article 21 of the Statute is mirrored after Article 36 (1) of the ICJ Statute, where the phrase ‘all matters’ is generally understood as referring to contentious procedures submitted to the Court pursuant to the consent of the parties, or participants respectively, involved (Ruys and Soete, 2016, 160; Tanaka, 2015, 326; You, 2008, 362). It has furthermore been stated that if States had wished to confer advisory jurisdiction upon the full Tribunal, they would have done so in express terms and by carefully delimitating the respective competence of the ITLOS (Ruys and Soete, 2016, 160). Attempts to rely on the doctrine of inherent powers (International Organizations or Institutions, Implied Powers), or the nature of the UNCLOS and its Annexes as ʻliving instrumentsʼ that ought to be interpreted in light of emerging subsequent practice, in order to justify the existence of an advisory jurisdiction of the full Tribunal (SRFC, Advisory Opinion (Separate Opinion of Judge Lucky), 2015, paras 18 ff) have been rejected by several commentators by reference to the fact that the requirements of these conceptions were, and are still, not fulfilled (Lando, 2016, 447 ff; Tanaka, 2015, 323; Ruys and Soete, 2016, 160; but see You, 2008, 363 f; García-Revillo, 2015, 312).

20  Other observers have attempted to justify the view that was later taken by the ITLOS by referring to the fact that the Statute does not prohibit the Tribunal to render an opinion on a point of law (Ndiaye, 2010, para 63; Jesus, 2006, 393 ff; see also SRFC, Advisory Opinion (Declaration of Judge Cot), 2015, para 4). It should be noted, however, that the legal basis of the jurisdiction of an international court or tribunal to settle inter-State disputes, or render advisory opinions on international legal questions respectively, ought to be regarded as resting on the principle of consent. This was indirectly confirmed by the ITLOS itself, which noted in its SRFC Advisory Opinion that in a case where the advisory jurisdiction of the Tribunal (allegedly) derives from an agreement in terms of Article 21 of the Statute, only the consent of those States party to that agreement is relevant (SRFC, Advisory Opinion, 2015, para 76). Acting on the assumption that the ITLOS would be competent to address any legal matter, unless the UNCLOS in general and the Statute in particular do not prohibit it to render a decision or opinion, implies that the consent of the States parties in relation to the jurisdiction of the Tribunal would extend to any issue not expressly prohibited. This is arguably difficult to accept, taking into account that the UNCLOS does indeed provide a provision concerning procedure before the Tribunal in relation to the advisory jurisdiction of the Seabed Disputes Chamber, but not of the full Tribunal (Tanaka, 2015, 328 ff). Accepting the rule ʻwhat is not prohibited is permittedʼ in the context relevant here would therefore face the risk of violating the sovereignty of the contracting parties to the Convention.

21  If one agrees with the view taken by the Tribunal that Article 21 of the Statute is not opposed to the existence of an advisory jurisdiction of the full Tribunal, but rather that it implicitly acknowledges the possibility that such jurisdiction is conferred to the Tribunal ʻin any other agreementʼ, this provision, together with the specific ʻother agreementʼ, constitute the joint legal basis for the jurisdiction of the ITLOS (SRFC, Advisory Opinion, 2015, para 58; but see Gao, 2015, para 12). The reference in Article 21 of the Statute to ʻany other agreement which confers jurisdiction on the Tribunalʼ provides that the principle of consent, which is the fundamental legal basis for the Peaceful Settlement of International Disputes, is complied with. That said, Article 21 of the Statute does not prescribe any formal requirements relating to how this consent is achieved (Lekkas and Staker, 2017, para 13). Thus, as a matter of principle even an implicit agreement to submit a legal dispute to the Tribunal, or a Stateʼs conduct that ought to be regarded as relevant under the rule of forum prorogatum respectively, would seem to suffice (Treves, 1995, 438–9; Eiriksson, 2000, 123–5).

22  However, Article 138 of the Rules, by requiring that the request for an advisory opinion submitted to the ITLOS is specifically provided for by an ʻinternational agreement related to the purposes of the Conventionʼ, does not seem to follow the extremely broad approach on which Article 21 of the Statute of the ITLOS is based–—provided that its relevance in relation to the existence of an advisory jurisdiction of the full Tribunal is accepted. The wording of Article 138 of the Rules reflects that of Article 288 (2) UNCLOS, which is why the argument can be made that both provisions should be interpreted coherently. This is particularly relevant in relation to whether Article 138 of the Rules, similar to Article 21 of the Statute, also includes ad hoc agreements between individual States, or between States and international organizations respectively, with the sole purpose of establishing the jurisdiction of the Tribunal. In its advisory opinion rendered on the request of the SRFC, the ITLOS did not have to address this question, as the request was based on Article 33 of the Convention on the Determination of the Minimal Conditions for Access and Exploitation of Marine Resources within the Maritime Areas under Jurisdiction of the Member States of the Sub-Regional Fisheries Convention (ʻMCA Conventionʼ), which undoubtedly qualifies as an international agreement related to the purposes of the UNCLOS.

23  It is submitted that this question ought to be answered in the negative (contra Jesus, 2006, 394). Different to Article 21 of the Statute, Article 288 (2) UNCLOS and Article 138 of the Rules do not refer to an agreement ʻwhich confers jurisdiction on the Tribunalʼ, but to an international ʻagreement related to the purposes of the Conventionʼ. This arguably presupposes the existence of an international treaty (no matter whether bilateral or multilateral) governing a substantive issue that is related to the purposes of the UNCLOS such as, say, the United Nations Agreement for the Implementation of the Provisions of the United Nations Convention on the Law of the Sea of 10 December 1982 relating to the Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks (ʻUNFSAʼ). While the necessary link to the purposes of the UNCLOS has been held to exist whenever this agreement affects an issue that is addressed by the Convention, irrespective of the degree of specificity (Mensah, 1999, 336), the agreement concerned must contain a procedural clause that provides for the advisory jurisdiction of the Tribunal in relation to a legal question concerning the interpretation and application of that very agreement (see, mutatis mutandis, Treves, 2017, para 8). This view is arguably reflected in the suggestion made by the President of the ITLOS, in his statement given at the 73rd session of the UN General Assembly in 2018, to consider the possibility of requesting the Tribunal for an advisory opinion in the potential future ‘international legally binding instrument under the United Nations Convention on the Law of the Sea on the conservation and sustainable use of marine biological diversity of areas beyond national jurisdiction’ (Statement by the President of the Tribunal, 2018, 6). If the contrary position were accepted, a minimum of two States would be in the position to request an advisory opinion of the ITLOS on any legal question arising in the context of the UNCLOS. In light of the fact that the Convention does not envisage a general advisory jurisdiction of the ITLOS, however, accepting that two or more States could invoke the jurisdiction of the Tribunal by concluding an agreement with the sole purpose of obtaining an advisory opinion on, say, the legality of another Stateʼs continental shelf delineation under the UNCLOS, would arguably constitute a circumvention of the requirements of Article 138 (1) of the Rules (contra Suarez, 2008, 231). Under a contextual interpretation of this provision, the mandate to expand the competence of the ITLOS under that provision can only apply in respect of legal questions arising under the ʻinternational agreementʼ referred to therein, not for other agreements such as the UNCLOS itself—with regard to which the scope of jurisdiction of the Tribunal is governed by its own terms. For the same reason, it is submitted that it is not possible for the Meeting of the States Parties to the UNCLOS to make a request for an advisory opinion, taking into account that the UNCLOS itself does not ʻspecifically provideʼ for the possibility of requesting an advisory opinion. As far as Article 21 of the Statute is concerned, the view advocated here provides a further reason for scepticism vis-à-vis the general existence of an advisory competence of the ITLOS as a full court, taking into account that this provision does not even require the agreement to be related to the purposes of the UNCLOS. Theoretically, the jurisdiction of the Tribunal could thus be extended also to issues that are not at all related to the law of the (see Written Statement of the United States of America, 27 November 2013, para 25). Thus, the members of the ITLOS, when adopting the Rules, seem to have recognized the need to include a procedural barrier in order to prevent that reference to its alleged advisory jurisdiction as a full Tribunal is made in abusive manner (see also García-Revillo, 2015, 312).

24  Similar to Article 288 (2) UNCLOS, but in contrast to Article 21 of the Statute, Article 138 para 1 of the Rules furthermore requires that the agreement which establishes the advisory jurisdiction of the Tribunal must be an ʻinternationalʼ one. It has been argued that an ʻinternational agreementʼ is an agreement concluded by entities that have the capacity to enter into treaty relationships under public international law, ie, States and international organizations (Treves, 1999, 354; Lekkas and Staker, 2017, para 14). Thus, the Tribunal seems to have opted against the possibility to exercise its advisory jurisdiction on the basis of agreements involving other entities such as private parties—a possibility that has been held to exist by commentators on the basis of Article 21 of the Statute (Wolfrum, 2008, 143).

25  Article 138 (1) of the Rules necessitates that the possibility to submit to the Tribunal a request to give an advisory opinion must be ʻspecifically provided forʼ in the international agreement related to the purposes of the UNCLOS. The narrow wording (ʻspecifically provides forʼ) of this provision arguably implies that the agreement concerned must explicitly envisage the advisory jurisdiction of the ITLOS in relation to a legal question that has arisen in relation to the interpretation and application of that agreement. As far as can be seen, the sole example of an agreement containing a relevant provision is the MCA Convention. According its Article 33, ʻ[t]he Conference of Ministers of the SRFC may authorize the Permanent Secretary of the SRFC to bring a given legal matter before the International Tribunal for the Law of the Sea for advisory opinion.ʼ The matter discussed here ought to be distinguished from determining to what matters the advisory jurisdiction of the Tribunal (provided that it exists) extends. In this respect, the ITLOS invoked the ʻspecifically provided forʼ formula contained in Article 21 of the Statute in its SRFC advisory opinion, and assessed whether the questions posed to it fell within the framework of the MCA Convention (SRFC, Advisory Opinion, 2015, para 67). It took a broader approach to the interpretation of this formula by holding that it would be sufficient if the questions presented to it have ʻa “sufficient connection” […] with the purposes and principles of the MCA Conventionʼ (SRFC, Advisory Opinion, 2015, para 68). Whether the Tribunal, as suggested by one commentator, thereby ʻadded a new prerequisite for its exercise of the advisory jurisdictionʼ (Gao, 2015, para 16) seems to depend on the relationship between Article 21 of the Statute and Article 138 (1) of the Rules on the other. If one agrees with the view taken by the Tribunal that Article 138 (1) of the Rules does not (and cannot) establish the advisory jurisdiction of the Tribunal, additional reference to the ʻspecifically provided forʼ formula codified in Article 21 of the Statute is arguably conclusive. This approach mirrors the limitation of the advisory jurisdiction of the ICJ contained in Article 96 (b) of the UN Charter, according to which UN organs other than the United Nations, General Assembly and the United Nations, Security Council, and specialized agencies—if authorized by the General Assembly—respectively, may only request advisory opinions of the ICJ ʻon legal questions arising within the scope of their activitiesʼ (Gao, 2015, para 16). Accordingly, the ITLOS is only entitled to exercise its advisory jurisdiction if (1) an international agreement related to the purposes of the UNCLOS expressly provides for the possibility to request an advisory opinion, and (2) this request is composed of legal questions that are substantially connected with the provisions of that very agreement.

26  If one accepts the existence of an advisory jurisdiction of the full Tribunal, the prerequisites concerning admissibility of the request for an advisory opinion must be met. According to Article 138 of the Rules, these prerequisites include that the request must be transmitted to the Tribunal by a body authorized by or in accordance with the international agreement that specifically provides for the possibility to submit a request to give an advisory opinion, and that such an opinion may be given only on legal questions (see also SRFC, Advisory Opinion, 2015, para 60).

27  According to Article 138 (2) of the Rules, a request for an advisory opinion shall be transmitted to the Tribunal ʻby whatever body is authorized by or in accordance with the agreement to make the request to the Tribunal.ʼ One commentator has argued that the ʻinterpretation of the term “body” under Article 138 of the Rules of the Tribunal is a crucial issue when considering the scope of the advisory jurisdiction of ITLOS as a full courtʼ (Tanaka, 2015, 336). Two different ways of interpretation have been proposed: under a broad reading, ʻany organ, entity, institution, organization or State that is indicated in such an international agreement as being empowered to request, on behalf of the parties concerned, an advisory opinion of the Tribunal, in accordance with the terms of the agreement, would be a “body” within the meaning of article 138, paragraph 2, of the Rulesʼ (Jesus, 2006, 394). In contrast, according to a restrictive interpretation of Article 138 (2) of the Rules, only international organizations can be ʻbodiesʼ, taking into account that an ITLOS advisory opinion could otherwise affect rights and obligations of third States without their consent (Tanaka, 2015, 337; Ndiaye, 2010, para 70; Treves, 2001, 98). Opposition against the broad view is closely related to the need to prevent abusive recourse to advisory proceedings before the ITLOS, but the wording of Article 138 (2) of the Rules (ʻby whatever bodyʼ) as well as its limited purpose arguably militate in favour of a flexible approach. In the words of one observer, ʻsuch body is only the conveyor of the request, [which is why] it seems to be of little relevance to dwell on the nature of such bodyʼ (Jesus, 2006, 394). It is submitted that the risk of abusive recourse to advisory proceedings can be sufficiently met by insisting on the international agreement in terms of Article 138 of the Rules containing a procedural clause that provides for the advisory jurisdiction of the Tribunal in relation to a legal question concerning the interpretation and application of that very agreement (see above para 22). If this requirement is taken seriously, there is no need to limit the scope of potential bodies to international organizations. The only condition that must be observed is that the competence of the body concerned to transmit the request to the Tribunal is derived from the international agreement and ʻnot by its nature or any other structural or institutional considerationsʼ (Jesus, 2006, 394).

28  According to Article 138 (1) of the Rules, an advisory opinion may only be given on a ʻlegal questionʼ. This requirement mirrors the one codified in Article 96 UN Charter, which is why reference can be made here to the relevant jurisprudence of the ICJ (Advisory Opinion: International Court of Justice (ICJ)). In its SRFC Advisory Opinion, the ITLOS referred to the fact that the questions posed by the SRFC had been framed in terms of law, and that it would be necessary to interpret the relevant provisions of the UNCLOS and the MCA Convention in order to respond to them (SRFC, Advisory Opinion, 2015, para 65).

29  Additionally, Article 131 (1) of the Rules, which according to Article 138 (3) of the Rules applies mutatis mutandis to advisory opinions, demands that a request for an advisory opinion must contain a precise statement of the question concerned, and that it shall be accompanied by all documents likely to throw light upon it. In the proceedings leading to the SRFC Advisory Opinion, doubts were expressed whether the abstract and general questions posed by the SRFC met the aforementioned requirements (eg Written Statement by the European Commission on behalf of the European Union, 29 November 2013, paras 6 ff; Second Written Statement by the European Commission on behalf of the European Union, 13 March 2014, paras 7 ff; see also Tanaka, 2015, 335). The ITLOS reacted to these doubts when analysing whether it would be entitled, or obliged respectively, to refuse to give the requested advisory opinion. By providing ʻthat the Tribunal may give an advisory opinionʼ, Article 138 (1) suggests that the Tribunal has some kind of discretionary power in deciding whether or not it renders the requested advisory opinion even if all admissibility requirements are fulfilled. In this respect, the ITLOS adopted the approach taken by the ICJ in the Nuclear Weapons Advisory Opinion (Nuclear Weapons Advisory Opinions), according to which a request for an advisory opinion should not in principle be refused except for ʻcompelling reasonsʼ (Nuclear Weapons, Advisory Opinion, 1996, para 14), and then assessed whether such reasons existed that should prompt it to not give the advisory opinion (SRFC, Advisory Opinion, 2015, paras 71 ff). Perhaps unsurprisingly, it took the view that the questions posed by the SRFC, while being abstract, would still be ʻclear enough to enable it to deliver an advisory opinionʼ (SRFC, Advisory Opinion, 2015, para 72). It furthermore refused to accept that the questions were only ʻcouched as legal questionsʼ, and that the SRFC would seek answers lex ferenda that would be outside the functions of the Tribunal as a judicial body (SRFC, Advisory Opinion, 2015, para 73). In this regard, however, the Tribunal merely stated that it would not ʻtake a position on issues beyond the scope of its judicial functionsʼ (SRFC, Advisory Opinion, 2015, para 74), but it did not provide any reasons, or safeguards respectively, in order to substantiate its clarification.

30  As far as the procedure requirements are concerned, Article 138 (3) of the Rules declares that the ʻTribunal shall apply mutatis mutandis articles 130 to 137.ʼ Thus, reference can be made here to the information provided in relation to advisory opinions rendered by the Seabed Disputes Chamber (see para 10 above; see also Chandrasekhara Rao and Gautier, 2018, para 4.327 ff).

31  Under Article 296 UNCLOS, the binding effect of decisions rendered by, eg, the ITLOS is limited to the ʻparties to the disputeʼ. This implies that advisory opinions, assuming that a corresponding jurisdiction of the Tribunal exists, do not have any binding legal effect. As was stated by the ICJ in its advisory opinion concerning the interpretation of peace treaties with Bulgaria, Hungary, and Romania, ʻ[t]he Court’s reply is only of an advisory character: as such, it has no binding forceʼ (Peace Treaties, Advisory Opinion, 1950, 81). With specific regard to the effects of advisory opinions rendered by the ITLOS as a full court, this was confirmed by the Tribunal in its SRFC Advisory Opinion, where it stated that the opinion ‘has no binding force and is given only to the SRFC’ (SRFC, Advisory Opinion, 2015, para 76). At the same time, it is quite clear that advisory opinions are not void of legal meaning. In addition to their moral authority (Ndiaye, 2010, para 52), advisory opinions of international courts and tribunals enjoy doctrinal authority, and they contribute to the establishment of a coherent case law corpus in the same way as judgments (Ndiaye, 2010, para 52, citing de Visscher, 1966, 195; see also Ago, 1991, 439 ff; Tanaka, 2018, 170–1). States that act in contradiction to what has been held by an international court’s or tribunal’s advisory opinion to reflect binding international law risk being made responsible by other States in future in the context of a contentious case. Furthermore, advisory opinions of international courts and tribunals have been accepted as falling within the scope of Article 38 (1) lit d of the ICJ Statute and thus constitute subsidiary means for the determination of rules of law (Pellet and Müller, 2019, paras 309, 320). As far as the specific impact of the SRFC Advisory Opinion is concerned, it has been submitted that by determining that flag States are, based on the general obligation to protect and conserve the marine environment, under a duty to take the necessary measures to ensure that ships flying their flag comply with the management measures adopted by a regional fisheries management organization within its area of territorial competence, the advisory opinion ought to be considered as a major step in the Tribunal’s approach to strengthening the regime for the protection of the marine environment (Proelss, 2019, 93 ff).

32  While the Seabed Disputes Chamber has been allocated compulsory advisory jurisdiction by the UNCLOS in relation to legal questions submitted by the Assembly and by the Council of the ISA arising within the scope of activities of these organs, the existence of an advisory jurisdiction of the Tribunal as a full court is still surrounded by uncertainties. In the view of the ITLOS, Article 21 of the Statute, together with the ʻother agreementʼ referred to by this provision, endows it with the competence to give advisory opinions on legal questions arising within the context of that agreement. In contrast, following up on written statements submitted by several States and organizations in the SRFC proceedings, commentators have expressed their doubts as to the existence of a general advisory jurisdiction of the Tribunal as well as to the persuasiveness of the interpretation of Article 21 of the Statute offered by the Tribunal. This criticism was also shared by several delegations during the 25th Meeting of States Parties to the UNCLOS, noting that the UNCLOS, including the Statute, did not expressively provide for any advisory jurisdiction beyond that bestowed upon the Seabed Disputes Chamber, and that ʻwhile jurisdiction could be conferred upon the Tribunal by an agreement other than the Convention, that jurisdiction should not extend to general matters beyond the scope of those agreementsʼ (Report of the Twenty-fifth Meeting of States Parties, para 23). If one attempts to strike a balance between the conflicting positions, it may be argued that the existence of an advisory jurisdiction of the full Tribunal can only be accepted on the basis of a narrow interpretation of the relevant conditions set out in Article 21 of the Statute and Article 138 of the Rules, which would prevent the Tribunal from claiming the role of a lawmaker, or initiating a trend of creeping jurisdiction respectively—a development that would arguably fundamentally challenge the crucial importance of the principle of consent as a legal basis for the settlement of disputes by international courts and tribunals.