1. Introduction
The adoption of the Agreement 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 (BBNJ Agreement)Footnote 1 in 2023 is widely considered a milestone for the governance of biodiversity in areas beyond national jurisdiction (ABNJ).Footnote 2 As the third implementing agreement of the United Nations Convention on the Law of the Sea (UNCLOS),Footnote 3 it aims to ‘ensure the conservation and sustainable use’Footnote 4 of marine biodiversity in ABNJ.Footnote 5 ABNJ encompass the high seasFootnote 6 and the ‘seabed and ocean floor and subsoil thereof’ beyond national jurisdiction (the ‘Area’).Footnote 7 The BBNJ Agreement, which entered into force on 17 January 2026, contains four separate pillars that, respectively, regulate marine genetic resources (Part II), area-based management tools (ABMTs – Part III), environmental impact assessments (EIAs – Part IV), and capacity building and the transfer of marine technology (Part V).Footnote 8
Throughout the negotiations, a key issue was the scope of the BBNJ Agreement’s mechanism for the establishment of ABMTs and its relationship with ‘relevant legal instruments and frameworks and relevant global, regional, subregional and sectoral bodies’ (IFBs) with relevant competences concerning the conservation and/or sustainable use of marine biodiversity in ABNJ.Footnote 9 The mechanism in Part III of the BBNJ Agreement enables the Conference of the Parties (CoP) of the BBNJ Agreement to decide on the establishment of legally bindingFootnote 10 ABMTs, including marine protected areas (MPAs),Footnote 11 in ABNJ.Footnote 12 However, in taking such decisions, the CoP must, under Article 22(2) BBNJ Agreement, ‘respect the competences of’ and ‘not undermine’ relevant IFBs.Footnote 13 Moreover, under Article 22(5) BBNJ Agreement, the CoP’s decisions and recommendations must ‘not undermine the effectiveness of measures adopted in respect of areas within national jurisdiction’ and must be made ‘with due regard for the rights and duties of all States, in accordance with [UNCLOS]’.
To assist the CoP’s decision-making with respect to the highly ambiguous legal constraints in Article 22 and other provisions of the BBNJ Agreement, Article 47(7) BBNJ Agreement introduces a novel mechanism by which the CoP may request an advisory opinion from the International Tribunal for the Law of the Sea (ITLOS or the Tribunal) on ‘a legal question on the conformity with [the BBNJ Agreement] of a proposal before the [CoP] on any matter within its competence’. As the provision’s design and most notably its explicit limitations indicate, the mechanism is designed primarily (albeit not exclusively Footnote 14 ) with the ABMT mechanism in mind.Footnote 15 For this reason, this article focuses on the contribution that the Tribunal’s advisory function under the BBNJ Agreement can make in the context of the CoP’s decision-making on ABMT proposals.
The idea of incorporating advisory opinions of ITLOS into the BBNJ Agreement was only reflected in the draft text at a relatively late stage of the negotiations. The suggestion had been made by several delegations, including those of Caribbean and Pacific island states,Footnote 16 and was first reflected in the ‘Further Revised Draft Text’ as Article 55ter.Footnote 17 Reactions were mixed: while some delegations welcomed the Tribunal’s advisory function as a way to clarify the legal framework of the Agreement, others expressed concern about jurisdictional overreach and institutional conflicts, particularly with respect to matters within the competence of IFBs.Footnote 18 The final version of the mechanism contained in Article 47(7) BBNJ Agreement reflects these concerns and differs significantly from earlier proposals by introducing jurisdictional prerequisites and limitations. While the advisory opinion mechanism has been touched upon in scholarship focusing on the dispute settlement provisions of the BBNJ Agreement,Footnote 19 the novelty and questions raised by the Tribunal’s advisory function under the BBNJ Agreement call for a detailed examination of its features.
Against this background, the aim of this article is to explore how the advisory opinion mechanism contributes to the lawful and effective establishment of ABMTs under the BBNJ Agreement, and to analyse the mechanism’s design in light of existing advisory opinion mechanisms and their increasing relevance in international judicial practice. To this end, this article examines the advisory opinion mechanism under Article 47(7) BBNJ Agreement, with a particular focus on the applicable procedural framework, the scope of advisory jurisdiction of the Tribunal and the function and potential of the advisory opinion mechanism in contributing to the legality, legitimacy and effectiveness of decision-making regarding ABMTs under Part III of the BBNJ Agreement. In a first step, Section 2 revisits ITLOS’s full-bench advisory jurisdiction under UNCLOS, including the contested question of its legal basis. Next, Section 3 examines how Article 47(7) BBNJ Agreement draws on this mechanism and outlines key procedural aspects. Section 4 analyses the prerequisites for advisory jurisdiction under said provision, while Section 5 addresses its ratione materiae limitations. Section 6 considers the legal significance of advisory opinions under this mechanism. Section 7 concludes.
2. Full-bench advisory opinions of ITLOS under UNCLOS
The inclusion of a mechanism for requesting advisory opinions from ITLOS in the BBNJ Agreement is not straightforward. While Article 191 UNCLOS provides for advisory jurisdiction of the Seabed Disputes Chamber of ITLOS (SDC) concerning requests by the Assembly and Council of the International Seabed Authority (ISA) ‘on legal questions arising within the scope of their activities’,Footnote 20 neither Part XV nor Annex VI of UNCLOS (hereinafter ITLOS StatuteFootnote 21 ) envisaged a competence of the full Tribunal to render advisory opinions.Footnote 22 This is particularly evident when UNCLOS is compared to treaties that explicitly confer advisory competence on an international court or tribunal, such as the International Court of Justice (ICJ).Footnote 23 Without a clear textual foundation in UNCLOS, the Tribunal itself adopted Article 138 of the Rules of the Tribunal (ITLOS Rules), which contemplates advisory proceedings before the full Tribunal.Footnote 24 This provision then went largely unnoticed and unopposed for almost 20 years.Footnote 25
Finally, in 2015, ITLOS had to take a stance on this issue in the first request for a full-bench advisory opinion in the SRFC Advisory Opinion.Footnote 26 In these proceedings, several states contested the Tribunal’s advisory jurisdiction.Footnote 27 The Tribunal, however, unanimously confirmed its advisory jurisdictionFootnote 28 – while noting that neither UNCLOS nor the ITLOS Statute expressly provided for such jurisdiction.Footnote 29 ITLOS identified Article 21 ITLOS Statute as the key provision, noting that it is not subordinate to Article 288 UNCLOS but ‘stands on its own footing’.Footnote 30 Under Article 21 ITLOS Statute, ITLOS has jurisdiction over ‘all disputes and all applications submitted to it in accordance with [UNCLOS]’ and ‘all matters specifically provided for in any other agreement which confers jurisdiction on the Tribunal’.
ITLOS considered the term ‘all matters’ to be broader than ‘disputes’Footnote 31 and to include advisory opinions if ‘specifically provided for in any other agreement which confers jurisdiction on the Tribunal’.Footnote 32 Thus, Article 21 ITLOS Statute and the ‘other agreement’ conferring jurisdiction on the Tribunal were ‘interconnected and constitute the substantive legal basis of the advisory jurisdiction of the Tribunal’.Footnote 33 Further, ITLOS concluded that Article 138 ITLOS Rules did not constitute the basis for the Tribunal’s advisory jurisdiction, but ‘only furnishes the prerequisites that need to be satisfied before the Tribunal can exercise its advisory jurisdiction’.Footnote 34 By making use of this mechanism, the BBNJ Agreement constitutes the third ‘other agreement’ conferring advisory jurisdiction on the full Tribunal.Footnote 35
While the Tribunal’s stance in the SRFC Advisory Opinion initially attracted much scholarly criticism,Footnote 36 the full Tribunal’s advisory jurisdiction can now be considered ‘a fait accompli’ that ‘is unlikely to be reversed in the future’.Footnote 37 Recent developments demonstrate that the question of whether full-bench advisory opinions of ITLOS are ultra vires should now be regarded as settled despite the dubious legal basis of the Tribunal’s advisory jurisdiction. First, the Tribunal unanimously reaffirmed the position in its prior jurisprudence in its latest COSIS Advisory Opinion in 2024.Footnote 38 Second, most participants in these proceedings ‘expressed the view that the Tribunal has jurisdiction to render the advisory opinion’.Footnote 39 Third, the BBNJ Agreement, including its Article 47(7), was adopted by consensus without a formal objection being raised by any of the remaining vocal opponents (specifically Brazil, India, and China) of the ITLOS’s expansion of its jurisdiction.Footnote 40 In particular, this last point suggests broad support or at least acquiescence by the vast majority, if not the entirety, of states parties to UNCLOS.Footnote 41
However, some legitimacy concerns remain with respect to the Tribunal’s full-bench advisory competence, in particular for requests based on a treaty between only a limited number of states (and possibly with the sole purpose to request advisory opinions).Footnote 42 That said, the legitimacy of full-bench advisory opinions based on Article 47(7) BBNJ Agreement is not subject to the same criticism given that only the CoP, the BBNJ Agreement’s plenary organ in which all parties are represented, has the power to make such requests (similar to the Assembly of the ISA under Article 191 UNCLOS).Footnote 43
3. Advisory opinion requests under the BBNJ Agreement
As shown in the previous section, the Tribunal’s jurisdiction to render advisory opinions upon request from the CoP derives from Article 21 ITLOS Statute in conjunction with Article 47(7) BBNJ Agreement, whereas the general prerequisites for the exercise of this jurisdiction are found in Article 138 ITLOS Rules. The advisory proceedings are governed by the ITLOS Statute (to the extent to which ITLOS recognizes the provisions of the ITLOS Statute relating to the procedure to be applicableFootnote 44 ) and Article 138(3) in conjunction with Articles 130–7 of the ITLOS Rules.Footnote 45 The following sections address the prerequisites of Article 138 ITLOS Rules and two additional procedural aspects: participation in advisory proceedings and the issue of requests for urgent proceedings.
3.1 Requirements of Article 138 ITLOS Rules regarding the request
Article 138 ITLOS Rules contains three key prerequisites for the exercise of advisory jurisdiction by ITLOS. The first two requirements are clearly fulfilled: There is no doubt that the BBNJ Agreement, as an implementing agreement of UNCLOS, is ‘an international agreement related to the purposes of [UNCLOS]’ within the meaning of Article 138(1) ITLOS Rules. Moreover, Article 47(7) BBNJ Agreement ‘specifically provides for the submission to the Tribunal of a request for … an [advisory] opinion’ as required by Article 138(1) ITLOS Rules.
Under Article 138(2) ITLOS Rules, a request for an advisory opinion must be transmitted to the Tribunal ‘by whatever body is authorized by or in accordance with the agreement to make the request’. Article 47(7) BBNJ Agreement explicitly confers this function upon the CoP. Notably, there had been discussion on additionally granting IFBs the right to request an advisory opinion.Footnote 46 It has been argued that this would have ensured an ‘equality of arms’ in matters concerning the allocation of competences between the CoP and IFBs.Footnote 47 Neither the BBNJ Agreement nor the draft of the Rules of Procedure of the CoP that were considered by the Preparatory Commission address the issue of the actual transmittal of the request to ITLOS.Footnote 48 The Tribunal has accepted transmittals by the ‘Permanent Secretary’ of the requesting international organization (on the basis of an explicit authorization in the respective agreement)Footnote 49 and by the ‘Co-Chairs’ of the treaty body making the requestFootnote 50 in its practice so far.Footnote 51 Therefore, absent (desirable) clarification in the future Rules of Procedure of the CoP, the SecretariatFootnote 52 or, alternatively, the President as the highest officer of the CoPFootnote 53 should be appropriate organs to transmit the request under Article 47(7) BBNJ Agreement.
Given that the request must also be made ‘in accordance with’Footnote 54 the BBNJ Agreement, the applicable decision-making procedures of the CoP must be complied with.Footnote 55 In principle, the CoP ‘shall make every effort to adopt decisions … by consensus’.Footnote 56 If consensus cannot be reached, the rules on the CoP’s decision-making differentiate between questions of substance and questions of procedure: The former are adopted by a two-thirds majority of the parties present and voting, whereas the latter are adopted by a majority of the parties present and voting.Footnote 57 Requesting an international tribunal to deliver a non-binding but authoritativeFootnote 58 answer on a legal question of importance is arguably a substantive rather than a purely procedural issue.
Against this background, a decision of the CoP to request an advisory opinion pursuant to Article 47(7) BBNJ Agreement must be treated as a ‘question of substance’,Footnote 59 thus requiring a two-thirds majority.Footnote 60 This is supported by the provision’s drafting history, with an earlier draft expressly requiring a two-thirds majority for such requests.Footnote 61 As the express two-thirds majority requirement was not replaced with another threshold, the drafters were likely in favour of applying the general provisions leading to the identical two-thirds majority threshold for questions of substance. This differs considerably from Article 159(10) UNCLOS, pursuant to which only a fourth of the members of the ISA are required to trigger a request for an advisory opinion from the SDC on the conformity of a proposal before the Assembly with UNCLOS.
3.2 Participation in advisory proceedings
The ITLOS Rules also govern the question of participation in the advisory proceedings.Footnote 62 These rules are of particular interest given the importance of IFBsFootnote 63 and other relevant stakeholders, including ‘civil society, the scientific community, the private sector, Indigenous Peoples and local communities’Footnote 64 in the context of the mechanism for the establishment of ABMTs in Part III BBNJ Agreement. Compared to contentious proceedings, advisory cases offer broader opportunities for states, IFBs and other stakeholders to participate in the proceedings.Footnote 65
According to a literal reading of Article 133 ITLOS Rules, all states parties to UNCLOS may participate by right regardless of whether they are also parties to the BBNJ Agreement. Furthermore, as the Tribunal stated in the COSIS Advisory Opinion, ‘intergovernmental organizations’ that are ‘likely to be able to furnish information on the question’Footnote 66 must be invited to make written and oral statements in the proceedings. Organizations not invited to participate may request to be invited.Footnote 67 The provision does not mention parties to the BBNJ Agreement. Nonetheless, UNCLOS non-parties (that are parties to the BBNJ Agreement) are not necessarily excluded from participating in advisory proceedings. In the SRFC Advisory Opinion, the Tribunal extended an invitation to the United States (an UNCLOS non-party) by virtue of being a state party to the UNFSA, an implementing agreement to UNCLOS to which the opinion pertained.Footnote 68 In advisory proceedings instituted under Article 47(7) BBNJ Agreement, ITLOS will likely uphold this practice in relation to parties to the BBNJ Agreement.Footnote 69 While this practice may arguably be justified as a liberal interpretation of Article 133 ITLOS Rules that takes into account the post-UNCLOS adoption of implementing agreements, a clarification of the ITLOS Rules in this regard would be desirable.
Additionally, much depends on the Tribunal’s interpretation of the term ‘intergovernmental organization’. Under Article 21(2)(b) BBNJ Agreement, consultations on proposals for the establishment of ABMTs must involve IFBs. Not all of these bodies are intergovernmental organizations in the strict sense.Footnote 70 At the same time, it is beyond doubt that these bodies ‘are likely to be able to furnish information on the question’ if they are ‘relevant’ in relation to a specific ABMT-proposal and invited to submit views during the BBNJ Agreement’s consultation process.
In some respects, the Tribunal has taken a broad approach, namely by admitting the International Union for Conservation of Nature (IUCN), which is ‘composed of governments and civil society organisations’,Footnote 71 as a participant.Footnote 72 However, while the Tribunal invited many regional fisheries management organizations (RFMOs) to participate in the SRFC Advisory Opinion based on whether they had been invited to attend the Thirtieth meeting of the Committee on Fisheries of the Food and Agriculture Organization of the United Nations, none of the existing regional fisheries management arrangements (RFMAs)Footnote 73 were included in the list of invited ‘intergovernmental organizations’.Footnote 74 RFMAs, such as the Southern Indian Ocean Fisheries Agreement (SIOFA),Footnote 75 have treaty bodies such as meetings or conferences of the parties, but are not generally considered international organizations (and thus RFMOs) sensu stricto.Footnote 76 Relevant multilateral environmental agreements such as the Convention on the Conservation of Migratory Species of Wild Animals (CMS)Footnote 77 were also not included on the list.Footnote 78 This practice may have changed in the COSIS Advisory Opinion proceedings, where the Tribunal invited the United Nations Framework Convention on Climate Change (UNFCCC),Footnote 79 a treaty with a CoP rather than an international organization, to participate (via its Secretariat).Footnote 80 Therefore, ITLOS may admit participation by relevant treaty bodies, including those that might not be universally considered international organizations in the strict sense, in the context of advisory opinions requested under Article 47(7) BBNJ Agreement. In selecting those bodies ‘which are likely to be able to furnish information on the question’, the Tribunal could consider the list of those bodies that were consulted in the context of the specific ABMT-related proposal.Footnote 81
Finally, the ITLOS Rules do not provide for any participatory status of the non-state actors other than IFBs mentioned in the BBNJ Agreement (‘civil society, the scientific community, the private sector, Indigenous Peoples and local communities’). In its current practice, ITLOS does not include amicus curiae submissions of NGOs in the official case file. It does, however, post them on a separate publicly accessible section of the website.Footnote 82 Nothing would in principle prevent the Tribunal from extending this practice to the other groups, such as Indigenous Peoples and local communities. There is no indication of a potential change in the Tribunal’s practice in this regard, although the Tribunal could of course change its Rules or practice if it desired.Footnote 83 There is certainly growing support for this idea in scholarly literature.Footnote 84
3.3 Procedure in cases of requests for urgent proceedings
The BBNJ Agreement includes the option that the CoP ‘may request that [the advisory opinion] be given as a matter of urgency’.Footnote 85 Article 47(7) BBNJ Agreement therefore differs from Article 191 UNCLOS, which requires that the SDC’s advisory opinions ‘shall be given as a matter of urgency’, without the need for a request. In case of a request for urgent delivery, ITLOS will ‘take all appropriate steps to accelerate the procedure’,Footnote 86 which may even include dispensing with oral proceedings altogether.Footnote 87 Rule 46 Draft Rules of Procedure of the CoP appears to envisage a rather speedy delivery of the advisory opinion (‘[i]f the advisory opinion is not received before the closure of the meeting during which it is requested …’).Footnote 88 This provision was apparently modelled on Article 159(10) UNCLOS, which deals with the deferment of proposals before the Assembly of the ISA pending a request for an advisory opinion.Footnote 89 However, based on the experience of the advisory proceedings before ITLOS and its SDC thus far, it seems unrealistic that the Tribunal would render an advisory opinion during the meeting of the CoP at which the opinion was requested.Footnote 90
4. Prerequisites for jurisdiction
In contrast to earlier drafts, which included the power of the CoP to seek an advisory opinion ‘on any legal question arising within the scope of [the BBNJ Agreement]’,Footnote 91 the final wording of Article 47(7) BBNJ Agreement significantly limits the scope of potential legal questions that can be submitted to ITLOS.Footnote 92 It restricts the scope of the advisory jurisdiction to requests ‘on a legal question on the conformity with [the BBNJ Agreement]’ of ‘a proposal before the [CoP] on any matter within its competence’. This differs considerably from the scope of advisory opinions under Article 191 UNCLOS (‘legal questions arising within the scope of [the Assembly’s and the Council’s] activities’),Footnote 93 Article 33 MCA Convention (‘a given legal matter’)Footnote 94 and Article 2(2) COSIS Agreement (‘any legal question within the scope of [UNCLOS]’ – although the provision’s introductory clause also makes a link to climate change, which could be read as limiting the substantive scope of legal questions).Footnote 95 At the same time, the similarities with the scope of advisory opinions under Article 159(10) UNCLOS, which allows (at least) one fourth of the members of the ISA to compel the Assembly of the ISA to request an advisory opinion from the SDC on ‘the conformity with [UNCLOS] of a proposal before the Assembly on any matter’ and to simultaneously ‘defer voting on that proposal pending receipt of the advisory opinion’, are striking.Footnote 96 As shown in the following sections, these two prerequisites result in a relatively narrow scope of the Tribunal’s advisory competence.
4.1 Proposal before the CoP on any matter within its competence
First, the jurisdiction ratione materiae of ITLOS is limited to questions concerning a ‘proposal before the [CoP] on any matter within its competence’. Two requirements can be deduced from this wording, the first procedural (proposal before the CoP) and the second substantive (matter within the CoP’s competence).
4.1.1 Proposal before the CoP
Procedurally, advisory jurisdiction is limited to situations in which there is a ‘proposal’ before the CoP. Thus, Article 47(7) BBNJ Agreement is closely connected to the CoP’s decision-making procedure, which is also evidenced by its location in Article 47, which comprises rules on the CoP’s general functioning and decision-making. Advisory opinions cannot therefore be requested in the absence of a proposal, or once a proposal has been adopted, rejected or withdrawn. Accordingly, while advisory opinions under Article 159(10) UNCLOS ‘serve to assist the Assembly [of the ISA] during its decision-making process’,Footnote 97 advisory opinions under Article 47(7) BBNJ Agreement have the corresponding function for the CoP. As ITLOS will give its advisory opinion already at the proposal stage, the CoP can base its subsequent decision on the Tribunal’s legal assessment, thereby avoiding the adoption of proposals that are not in conformity with the BBNJ Agreement.
There are, however, some differences between Article 159(10) UNCLOS and Article 47(7) BBNJ Agreement. Only a fourth of the members of the ISA are required to trigger a request under Article 159(10) UNCLOS and, importantly, also the deferral of voting on the proposal. This empowers a minority of ISA members to defer a proposal and subject it to legal review by the SDC – although the proposal could have been adopted by a two-thirds majority of the members against the opposition of this minority.Footnote 98 By contrast, the threshold of a two-thirds majority for a request under Article 47(7) BBNJ Agreement is very high and does not involve an automatic deferral of voting on the proposal (although an automatic deferral might be incorporated in the Rules of Procedure of the CoP – and in any event the two-thirds majority adopting the decision to request an advisory opinion will be able to block the adoption of the relevant proposal before the CoP).Footnote 99 Hence, the advisory opinion mechanism under the BBNJ Agreement does not afford much protection to a minority of parties that oppose a proposal unless a sufficient number of members in the majority agrees with this minority that a request for an advisory opinion should be submitted to the Tribunal.
Given that Article 47(7) BBNJ Agreement does not specify the subject-matter of proposals that can form the basis of a request for an advisory opinion, it arguably includes any proposal before the CoP regardless of subject-matter. This interpretation is supported by the advisory opinion mechanism’s location in Part VI of the BBNJ Agreement (entitled ‘Institutional Arrangements’) and specifically in Article 47. Indeed, it is one of the CoP’s main functions to ‘[a]dopt decisions and recommendations related to the implementation of [the BBNJ Agreement]’.Footnote 100 Specific powers of the CoP to adopt decisions and recommendations are manifold and may be found throughout the BBNJ Agreement.Footnote 101 However, in the text of the BBNJ Agreement, the term ‘proposal’ is only expressly used for decisions pertaining to the establishment of ABMTs under Part III.Footnote 102 Accordingly, the use of the word ‘proposal’ in Article 47(7) BBNJ Agreement indicates that the advisory opinion mechanism, while applicable to any draft decision text proposed for adoption by the CoP,Footnote 103 is most relevant in the context of CoP decisions on the establishment, modification, or revocation of ABMTs (which in turn is the most important law-making mandate of the CoP).Footnote 104 This view finds support in the limitations to jurisdiction contained in Article 47(7) BBNJ Agreement, which are most relevant in the context of ABMTs.Footnote 105 For this reason, the following analysis will focus specifically on proposals related to ABMTs.
4.1.2 Matter within the competence of the CoP
Additionally, Article 47(7) BBNJ Agreement requires the ‘proposal before the [CoP]’ to be ‘within its competence’. In contrast to Article 191 UNCLOS, there needs to be a positive judicial determination that the matter falls within the competence of the CoP. It is not sufficient that the matter ‘arose’ within the scope of the CoP’s activities.Footnote 106 Advisory opinions under the BBNJ Agreement are thus more strictly limited to the competence of the CoP. In the context of the CoP’s competence to establish ABMTs under Part III of the BBNJ Agreement, legal questions posed in a request for an advisory opinion will likely include whether a matter falls within the competence of the CoP.Footnote 107 This raises a fundamental question about the extent of the CoP’s competence to adopt ABMTs in light of the two distinctFootnote 108 obligations to ‘respect the competences of, and not undermine’ IFBs.Footnote 109 That said, the scope of the CoP’s competence and the limits imposed on the exercise of this competence should be distinguished. Part III of the BBNJ Agreement, and specifically Article 22(1), provide for the general competence of the CoP to establish ABMTs, including MPAs, and related measures in ABNJ.Footnote 110
The CoP’s subject-matter competence is concretized via the definition of the term ABMT, which clarifies that ABMTs contain measures ‘through which one or several sectors or activities are managed with the aim of achieving particular conservation and sustainable use objectives in accordance with [the BBNJ Agreement]’.Footnote 111 There is no provision anywhere in the BBNJ Agreement that further concretizes the ‘sectors’ or ‘activities’ that may be regulated through ABMTs.Footnote 112 Accordingly, the general subject-matter scope of the CoP’s ABMT-competence is comprehensive.Footnote 113 The obligations to ‘respect the competences of’ and ‘not undermine’ IFBs in Article 22(2) BBNJ Agreement only constrain the exercise of the CoP’s comprehensive ‘residual’ competence to prevent an ABMT-proposal from encroaching upon an IFB’s competenceFootnote 114 or from otherwise ‘undermining’ an IFB.
The position taken here is best illustrated with a hypothetical example: There is no doubt that the CoP can establish an ABMT in the high seas of the Northwest Indian Ocean (outside the current scope of the SIOFA Area) that imposes, inter alia, restrictions on fishing for squid.Footnote 115 If the SIOFA Area were subsequently extended to cover the high seas of the Northwest Indian Ocean, the CoP would arguably no longer be able to lawfully adopt the same measures against the (hypothetical) opposition of SIOFA, as it would then fail to ‘respect the competences’ of SIOFA.Footnote 116 The CoP’s comprehensive ‘residual’ ABMT-competence (which still exists) must not be exercised when a competing IFB competence exists and the IFB opposes the establishment of an ABMT by the CoP or is unable to reach a decision in support of action by the CoP (although it is a matter for further debate if the CoP has some leeway to act if the IFB is deadlocked on an issue within its competence).Footnote 117 The scope of the Tribunal’s advisory jurisdiction in principle extends to all proposals made in line with the CoP’s comprehensive ‘residual’ ABMT-competence. The question whether the proposal additionally falls into the competence of an IFB, and therefore raises questions of conformity with Article 22(2) BBNJ Agreement, only becomes relevant with respect to the respective limitation to jurisdiction, which is addressed in Section 5.1. It may thus be concluded that the prerequisite that the proposal must be ‘within [the CoP’s] competence’ does not pose a significant jurisdictional hurdle.
4.2 Legal question on the proposal’s conformity with the BBNJ Agreement
Pursuant to Article 47(7) BBNJ Agreement, the request must furthermore be ‘on a legal question on the conformity with [the BBNJ Agreement]’ of a proposal before the CoP. As noted, this differs from broader mechanisms such as Article 191 UNCLOS and confines the scope of advisory opinions to a review of the legality of proposals under the BBNJ Agreement.
While the Tribunal’s jurisdiction is limited to the question of the conformity with the BBNJ Agreement as a whole, the Agreement also contains provisions which can be classified, to different degrees, as rules of reference (or ‘renvoi’).Footnote 118 In determining whether a proposal, if adopted as a decision, would result in a violation of a provision containing a renvoi, the Tribunal will be able to consider rules external to the BBNJ Agreement. For example, reliance on UNCLOS provisions may be necessary in assessing the conformity of a proposal with Article 5(1) BBNJ Agreement (‘shall be interpreted and applied in the context of and in a manner consistent with [UNCLOS]’) or Article 22(5) BBNJ Agreement, which requires the CoP’s decisions and recommendations to ‘not undermine the effectiveness of measures adopted in respect of areas within national jurisdiction’ and to ‘be made with due regard for the rights and duties of all States, in accordance with [UNCLOS]’.Footnote 119
Similarly, an assessment of a proposal’s conformity with the obligations to ‘respect the competences of’ and ‘not undermine’ IFBs under Article 22(2) BBNJ Agreement may require determinations in relation to an IFB’s constitutive legal instrument (for the purpose of delimiting its de jure competence in the context of the obligation to respect) and/or policies and measures (for the purpose of ascertaining de facto effects in the context of the obligation to not undermine).Footnote 120 For example, in order to assess the conformity with Article 22(2) BBNJ Agreement of a hypothetical proposal to establish an ABMT in the high seas of the Indian Ocean that includes a prohibition on bottom trawling for certain species of fish, it could be necessary to determine the scope of SIOFA’s geographical and subject-matter competence under the SIOFA Agreement.Footnote 121
Overall, the conformity of ABMT-proposals with paragraphs 2 and 5 of Article 22 BBNJ Agreement is among the most likely subject-matters of future requests for an advisory opinion from ITLOS. That said, insofar as questions of competence are concerned, there is a possibility that the Tribunal will have to decline jurisdiction on the basis that the request seeks an advisory opinion ‘on a matter within the competences’ of one or more IFBs – as discussed in Section 5.1 below.
5. Limitations to jurisdiction
A special feature of the Tribunal’s advisory competence under the BBNJ Agreement is that Article 47(7) contains three limitations to advisory jurisdiction ratione materiae for certain categories of subject-matters (to be distinguished from the discretionary possibility of declining out of judicial propriety a request for an advisory opinion, for which there is jurisdiction, if there are ‘compelling reasons’Footnote 122 ). The scope of the Tribunal’s advisory jurisdiction excludes any matter (i) that is ‘within the competences of other global, regional, subregional or sectoral bodies’, (ii) ‘that necessarily involves the concurrent consideration of any dispute concerning sovereignty or other rights over continental or insular land territory or a claim thereto’ or (iii) ‘that necessarily involves the concurrent consideration of any dispute concerning … the legal status of an area as within national jurisdiction’. These limitations were not included in early drafts during the negotiationsFootnote 123 and the third limitation was only added in the final text.Footnote 124 Limiting the Tribunal’s jurisdiction in this way is novel given that limitations and exceptions to jurisdiction ratione materiae have traditionally been incorporated into compulsory dispute settlement mechanisms applicable to contentious cases, but not into provisions on advisory competence.Footnote 125
5.1 Matters within the competences of other bodies
The first limitation reflects the BBNJ Agreement’s concern with the protection of IFB competences from overreach by the CoP and, by extension, the Tribunal as a judicial body from which the CoP can request an advisory opinion. It excludes requests ‘on a matter within the competences of other global, regional, subregional or sectoral bodies’ (hereinafter ‘relevant bodies’) from the scope of the Tribunal’s advisory jurisdiction. Notably, this wording does not mention IFBs generally but only mentions ‘bodies’ and not also ‘legal instruments and frameworks’, which could imply a narrower scope than, for example, Article 22(2) BBNJ Agreement. That said, the term ‘bodies’ is arguably broad enough to cover all international organizations and treaty bodies involved in law-making (including, for example, both RFMOs and RFMAs).
As it is already an explicit prerequisite for advisory jurisdiction that the matter is within the CoP’s (residual) competence,Footnote 126 this limitation only becomes relevant when the CoP’s competence overlaps with that of a relevant body.Footnote 127 As the limitation curtails ITLOS’s jurisdiction in these cases, it has been suggested that it is ‘very far-reaching and problematic’Footnote 128 and ‘may even prevent the Tribunal from considering whether a proposal under the [CoP] would undermine the [relevant body]’.Footnote 129 If true, the limitation would be detrimental to the advisory opinion’s purpose of clarifying the legality of an ABMT-proposal. It would preclude ITLOS from answering the central question of a proposal’s conformity with the obligations to ‘respect the competences of’ and ‘not undermine’ IFBs under Article 22(2) BBNJ Agreement – possibly the most important legal question that would be posed in a request for an advisory opinion in practice.
Therefore, in the light of the advisory opinion’s objective to assist the CoP with legal advice in the ABMT establishing process, an interpretation of the limitation that allows ITLOS to assess a proposal’s conformity with (aspects of) Article 22(2) BBNJ Agreement – or at least enables the Tribunal to determine whether a proposal falls within the competence of a relevant body – would be desirable. It is submitted that there are two interpretive approaches that would at least partially salvage the function of the advisory opinion mechanism.
The first interpretation is that ITLOS, in determining whether the limitation to jurisdiction applies, has jurisdiction to positively determine whether the ‘matter’ on which an advisory opinion is sought falls ‘within the competences’ of one or more bodies.Footnote 130 This approach ensures that ITLOS effectively exercises its mandate under Article 47(7) BBNJ Agreement and Article 21 ITLOS Statute to render an advisory opinion following a request over which it has advisory jurisdiction. This is confirmed by existing jurisprudence on other limitations and exceptions to jurisdiction ratione materiae, such as those in Article 298(1) UNCLOS. In determining whether an optional exception to jurisdiction under this provision is applicable, UNCLOS tribunals consider the question of whether the relevant claim of the applicant falls into an excepted category of dispute.Footnote 131 In the present context, this would mean that the Tribunal would have jurisdiction to determine whether the scope of the competence of the relevant body under its constitutive instrument (which the Tribunal may interpret and apply) covers the proposal before the CoP.
The downside of this first interpretation is that if the Tribunal determines that a matter is ‘within the competences of’ a relevant body, the Tribunal must inevitably decline jurisdiction. However, in doing so, it will have had the opportunity to provide an answer to the key question of competence, which in turn could serve as the basis for the CoP’s own consideration of a proposal’s conformity with the obligations to ‘respect the competences of’ and ‘not undermine’ IFBs under Article 22(2) BBNJ Agreement. While this result is unsatisfactory in light of the primary function of the advisory opinion mechanism, it still retains some relevance for this mechanism even in the context of the delimitation of competences.
A second, more expansive interpretation would not only permit the Tribunal to determine whether the relevant proposal falls within the competence of a relevant body, but also whether it actually fails to respect the body’s competence in violation of Article 22(2) BBNJ Agreement. If this approach is accepted, ITLOS would not automatically have to decline jurisdiction once the question of overlap of competence with the body is answered, but could proceed to answer the question whether the proposal is in conformity with Article 22(2) BBNJ Agreement. However, further determinations pertaining to the substance of a matter within the competence of the relevant body (such as whether the proposed ABMT would be sufficiently science-based and precautionary, or whether it would be in conformity with UNCLOS) would arguably be excluded from advisory jurisdiction because they would be ‘on a matter within the competences of’ the relevant body.
While it remains to be seen how the Tribunal will interpret this limitation to jurisdiction in practice, it is clear that there exists – at the very least – a path allowing for the determination of whether a ‘global, regional, subregional or sectoral body’ has an overlapping competence or not.
5.2 Implicated sovereignty disputes
Article 47(7) BBNJ Agreement excludes from the advisory jurisdiction of the Tribunal any requests ‘on a matter that necessarily involves the concurrent consideration of any dispute concerning sovereignty or other rights over continental or insular land territory or a claim thereto’ (emphasis added). This wording, which appears to be inspired by Article 298(1)(a) UNCLOS, shows that this limitation aims to constrain the exercise of so-called ‘incidental jurisdiction’ by ITLOSFootnote 132 over territorial sovereignty disputes that are implicated by questions relating to the BBNJ Agreement put to the Tribunal. Incidental jurisdiction is ‘the jurisdiction ratione materiae of an international adjudicatory body to adjudicate an incidental issue ordinarily outside of the body’s jurisdiction … but brought within it because the issue is incidental to another issue within the body’s jurisdiction’.Footnote 133
Unlike in domestic legal systems, incidental jurisdiction poses considerable challenges for international courts and tribunals as there is an inherent tension between the principle of consent to jurisdiction and the effective exercise of the relevant forum’s treaty-based judicial mandate in contentious cases.Footnote 134 Accordingly, two requirements for an exercise of incidental jurisdiction are widely accepted in the context of contentious cases: (i) ‘necessity’, meaning that a question within the primary jurisdiction of the court or tribunal cannot be decided without also deciding the external issue,Footnote 135 and (ii) ‘ancillarity’.Footnote 136 The latter, in simplified terms, relates to the appropriateness of exercising incidental jurisdiction over an external issue in the specific context. Different tests have been applied and/or proposed for this purpose.Footnote 137
It is unusual that Article 47(7) BBNJ Agreement, a provision on (non-binding) advisory opinions, includes limitations to incidental jurisdiction, as the doctrine of incidental jurisdiction has been developed in the context of contentious proceedings leading to binding decisions. That said, based on the so-called Eastern Carelia doctrine initially developed by the Permanent Court of International Justice (PCIJ),Footnote 138 the ICJ considers it possible to decline a request for an advisory opinion based on judicial propriety if ‘a reply would have the effect of circumventing the principle that a State is not obliged to allow its disputes to be submitted to judicial settlement without its consent’.Footnote 139 Similarly, ITLOS has recognized that one of the ‘compelling reasons’ due to which it may decline to exercise its advisory jurisdiction is that ‘the questions raised in the [r]equest may be closely related to questions which are the subject of a dispute affecting the rights and obligations of third States that have not consented to the [r]equest’.Footnote 140 However, unlike the PCIJ, the ICJ and ITLOS have never declined to render an advisory opinion for this reason even when faced with highly politicized questions of sovereignty.Footnote 141 Against this background, it is perhaps unsurprising that some states insisted on excluding incidental determinations on implicated sovereignty disputes at the level of advisory jurisdiction rather than leaving this question to the discretion of the Tribunal.Footnote 142
The limitation on the Tribunal’s exercise of incidental jurisdiction over implicated sovereignty disputes clearly falls within a broader trend in the jurisprudence of UNCLOS tribunals in contentious cases. Arbitral tribunals established under Annex VII of UNCLOS and the Special Chamber in Mauritius/Maldives have consistently held that they lack jurisdiction under Article 288(1) UNCLOS over UNCLOS-based claims that necessarily involve a concurrent consideration of implicated territorial sovereignty issues.Footnote 143 The arbitral tribunals in Mauritius v. United Kingdom and Ukraine v. Russia additionally considered that they could potentially exercise incidental jurisdiction over ‘a minor issue of territorial sovereignty’ that could be characterized as merely ‘ancillary’ to a primary dispute concerning the interpretation or application of UNCLOS.Footnote 144 Subsequently, the Special Chamber of ITLOS in Mauritius/Maldives held that the United Kingdom’s claim to sovereignty over the Chagos Archipelago no longer gives rise to a dispute with Mauritius due to the authoritative determinations made by the ICJ in its advisory opinion on the matter.Footnote 145 While the Special Chamber agreed with the existing jurisprudence by finding that it had no jurisdiction over territorial sovereignty disputes (without any reference to incidental jurisdiction over ‘ancillary’ sovereignty questions),Footnote 146 it was criticized for departing from existing jurisprudence insofar as the sovereignty dispute between the United Kingdom and Mauritius had not been settled in a binding fashion by the ICJ’s advisory opinion.Footnote 147 Regardless of whether one agrees or disagrees with the reasoning in Mauritius/Maldives, the case may be distinguished from the earlier cases in particular due to the existence of the ICJ’s advisory opinion and is thus not entirely irreconcilable with the remainder of the jurisprudence.Footnote 148
In addition to the described case-law, the contested nature of the question of incidental jurisdiction over implicated issues has begun to manifest itself in recent treaty-making in other fields (albeit with respect to contentious proceedings): Article 11.2(b) WTO Fisheries Subsidies AgreementFootnote 149 prohibits a panel established under Article 10 WTO Fisheries Subsidies Agreement as well as an arbitrator under Article 25 Dispute Settlement Understanding (DSU)Footnote 150 from making ‘findings with respect to any claim that would require it to base its findings on any asserted territorial claims or delimitation of maritime boundaries’.Footnote 151
The limitation in Article 47(7) BBNJ Agreement is clearly another manifestation of this restrictive trend, albeit transferred into the realm of advisory jurisdiction (in addition to contentious dispute settlement, see Article 60(9) BBNJ Agreement), where it would arguably not otherwise apply. It covers any questions in a request that involve concurrent consideration of an implicated sovereignty dispute unless such concurrent consideration is not ‘necessary’. It is more restrictive than the approach in Mauritius v. United Kingdom and Ukraine v. Russia: even implicated sovereignty disputes that are merely ‘ancillary’ to the request of the CoP will deprive ITLOS of advisory jurisdiction.Footnote 152 Based on the approach of the Special Chamber of ITLOS in Mauritius/Maldives,Footnote 153 the term ‘dispute’ may potentially present ITLOS with some flexibility in that there may be cases where prior determinations can be considered sufficiently authoritative to argue that there is normatively no sovereignty ‘dispute’ – although such a step should not be taken lightly in the face of an objectively existing sovereignty dispute.Footnote 154
5.3 Legal status of an area as within national jurisdiction
The third limitation to jurisdiction in Article 47(7) BBNJ Agreement applies to ‘a matter that necessarily involves the concurrent consideration of any dispute concerning … the legal status of an area as within national jurisdiction’. This limitation covers questions that can only be answered by determining, through an exercise of incidental jurisdiction, a disputed question concerning whether a specific area falls within the national jurisdiction of a coastal state rather than forming part of ABNJ (i.e. the high seas or the Area) within the scope of the BBNJ Agreement.Footnote 155
This could become necessary where an advisory opinion concerns a proposed ABMT in an area that the proponents claim to form part of ABNJ but that is simultaneously claimed by one or more states as being within their national jurisdiction. Notably, beyond the general restriction of the BBNJ Agreement’s scope to ABNJ,Footnote 156 Article 18 explicitly excludes areas within national jurisdiction from the scope of the ABMT-mechanism.Footnote 157 The legality and validity of a maritime claim depend on whether it is in conformity with UNCLOS and/or customary international law, meaning that illegal claims are not generally opposable to other states (meaning that the claimed areas would remain part of ABNJ).Footnote 158
There are many examples of hypothetical situations in which this limitation could become relevant.Footnote 159 They include the delineation of the Exclusive Economic Zone (EEZ) under Article 57 UNCLOS or the (extended) continental shelf of a coastal state under Article 76 UNCLOS. Such disputes may arise, for example, when the legality of a coastal state’s baselines – and by extension the extent of its maritime entitlements measured from the baseline – is contested.Footnote 160 Other examples include contested classification of a maritime feature as territory generating maritime entitlementsFootnote 161 or as an island ‘proper’ under Article 121(1) UNCLOS.Footnote 162 Compliance with the specific rules of extended continental shelf delineation under Article 76(8) UNCLOS can also be an issue,Footnote 163 such as in the context of the claim made in 2023 by the United States, an UNCLOS non-party.Footnote 164
The central South China Sea presents a particularly illustrative example. To this day, China claims the central South China Sea as an area within its national jurisdiction,Footnote 165 although the precise content and legal basis of the claim, including the meaning of the so-called U-shaped line, remain unclear.Footnote 166 With this position, China defies the award of the arbitral tribunal in the South China Sea Arbitration, which found that none of the features forming part of the Spratly Islands qualified as islands ‘proper’, thereby creating a pocket of high seas in the central South China Sea.Footnote 167 Additionally, the arbitral tribunal concluded that China’s claim to the South China Sea did not amount to a claim to historic watersFootnote 168 (in which China would enjoy sovereigntyFootnote 169 ) and that China could also not claim historic rights short of sovereignty that would entail sovereign rights over living and non-living resources.Footnote 170
It has been argued that the findings of the arbitral tribunal in the South China Sea Arbitration render the limitation in Article 47(7) BBNJ Agreement inapplicable with respect to disputes relating to the legal status of the central South China Sea.Footnote 171 However, as emphasized by Article 296(2) UNCLOS, awards of arbitral tribunals under Annex VII of UNCLOS have ‘no binding force except between the parties and in respect of that particular dispute’.Footnote 172 It would arguably be incompatible with this inter partes effect of judicial pronouncements in contentious cases under Part XV of UNCLOS if they could remove the existence of a dispute involving non-parties to the proceedings (such as, for example, a dispute between China and Vietnam or the United States).Footnote 173 While it has been proposed that this hurdle may be overcome by applying the jurisprudence of the Special Chamber of ITLOS in Mauritius/Maldives discussed above in the context of implicated sovereignty disputes,Footnote 174 the differences between decisions in contentious cases and advisory opinions militate against any such analogy – which in any event finds no support in the judgment in Mauritius/Maldives. Therefore, it cannot be ruled out that the limitation in Article 47(7) BBNJ Agreement may apply to the situation in the central South China Sea. Indeed, China’s overall position at the BBNJ Agreement negotiations, which emphasized ‘the principle of respecting territorial sovereignty and maritime rights and interests of countries’Footnote 175 suggests that the limitation to advisory jurisdiction for questions concerning the legal status of an area as within national jurisdiction may possibly be traced back (at least in part) to the contested status of the mentioned high seas pocket in the central South China Sea that was ‘created’ by the arbitral tribunal in the South China Sea Arbitration.Footnote 176
Climate change-induced sea-level rise may result in physical changes that could also affect geographical and other circumstances relevant to maritime entitlements.Footnote 177 In a recent development, the ICJ stated in its Climate Change Advisory Opinion that affected states are under no obligation ‘to update their charts or lists of geographical co-ordinates that show the baselines and outer limit lines of their maritime zones once they have been duly established in conformity with [UNCLOS]’.Footnote 178 While the ICJ did not explicitly state that baselines (and, accordingly, the outer limits of maritime zones measured from the baseline) are fixed rather than ambulatory in such situations, this has been argued to be implied in the absence of an obligation to ‘update … charts or lists of geographical co-ordinates’.Footnote 179 While such a definitive conclusion may be premature, the advisory opinion can be seen as another step in this direction.Footnote 180 Therefore, it cannot be ruled out that the limitation to advisory jurisdiction for questions concerning the legal status of an area as within national jurisdiction will be relevant in situations where maritime entitlements are contested as a result of sea-level rise.
A further likely candidate for future disputes about the applicability of the BBNJ Agreement is Antarctica.Footnote 181 The Antarctic claimantsFootnote 182 have asserted maritime claims (in some cases including EEZs and continental shelves) in the waters off their claimed Antarctic territories.Footnote 183 However, (parts of) these maritime claims face opposition by other states due to the contested nature of the territorial claims and/or on the basis of Article IV of the Antarctic Treaty, leaving the legal status of the waters off Antarctica as ABNJ or areas within national jurisdiction unclear.Footnote 184 Indeed, a number of states, such as Japan, explicitly treat the Southern Ocean as part of the high seas and reject the classification of these waters as within national jurisdiction.Footnote 185 Accordingly, disputes may arise in the context of the BBNJ Agreement as to whether the relevant areas are ABNJ in which ABMTs may be established – which in turn may result in the applicability of the limitation to jurisdiction concerning such disputes.Footnote 186 This gains additional relevance in light of the fact that the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has been a pioneer in developing MPAs in its Convention Area.Footnote 187 The potential overlap in competence makes CCAMLR a focal point for legal questions on the BBNJ Agreement’s ABMT-mechanism.Footnote 188
6. Legal significance of advisory opinions
The preceding sections discussed the prerequisites for and limitations of advisory jurisdiction in detail. Assuming that a request falls within advisory jurisdiction, the question of the legal significance of an advisory opinion under the BBNJ Agreement arises. In this respect, the starting point is that if the Tribunal finds that a proposal is not in conformity with the BBNJ Agreement, this finding will only be declaratory as advisory opinions of ITLOS do not have binding legal effects.Footnote 189 Yet, the importance of advisory opinions as authoritative judicial determinations should not be underestimated in the light of findings such as that of the Special Chamber of ITLOS in Mauritius/Maldives that ‘judicial determinations made in advisory opinions carry no less weight and authority than those in judgments’.Footnote 190
Moreover, as the advisory opinion will only address the relevant proposal and not a subsequent decision of the CoP, the Tribunal’s findings will primarily inform the CoP’s decision-making.Footnote 191 Findings of non-conformity should result in a rejection of the proposal or its modification in line with ITLOS’s interpretation of the requirements of the BBNJ Agreement. In this context, it may not necessarily be problematic if the Tribunal declines jurisdiction over the request on the basis that a matter is not within the CoP’s competenceFootnote 192 or is within the competence of an IFB.Footnote 193 What is decisive is whether the Tribunal’s reasoning in this respect is sufficiently instructive to allow the CoP to avoid violations of the relevant provisions of the BBNJ Agreement, such as the obligations to ‘respect the competences of’ and ‘not undermine’ IFBs.Footnote 194 In some cases, a finding on the question of the CoP’s and a relevant IFB’s competences, even when provided in the context of an advisory opinion of ITLOS that declines advisory jurisdiction, may provide sufficient legal clarity for the CoP’s decision-making.Footnote 195
More difficult questions arise if the CoP chooses to adopt an unlawful decision despite clear findings in an advisory opinion regarding a proposal’s non-conformity with the BBNJ Agreement. In line with the general rules of international institutional law, the CoP must perform its functions in accordance with the substantive and procedural rules contained in the BBNJ Agreement, which is the CoP’s constituent instrument.Footnote 196 Otherwise the relevant decision constitutes an ultra vires act, which, depending on the view taken, could be considered either (i) valid unless invalidated by a competent review body,Footnote 197 or (ii) an absolute nullity (i.e., void ab initio) depending on the severity of the irregularity.Footnote 198 Either way, it is clear that the CoP, as the body that will have taken the unlawful decision, will have the power and responsibility to revoke or amend an identified ultra vires decision.
In the absence of a mechanism pursuant to which an advisory opinion could be sought on the conformity of a decision with the BBNJ Agreement,Footnote 199 parties opposing the proposal could potentially consider this decision an ultra vires act of the CoP that is null and void ab initio. Where this is the case, parties may lawfully refuse to comply with the decision – both individually and in the framework of IFBs. However, absent a judicial determination, such non-compliance presents a considerable risk of a violation of the BBNJ Agreement. Accordingly, any opposing party might prefer to lodge, within a timeframe of 120 days after the CoP meeting, a unilateral objection to the respective decision on the ground that the decision is ‘inconsistent with [the BBNJ Agreement]’,Footnote 200 in which case the decision will not become binding on the objecting party.Footnote 201 This would, however, also trigger obligations to adopt alternative measures of equivalent effect and to not undermine the effectiveness of the decision.Footnote 202 Compliance with these obligations might not seem acceptable to a party that considers the relevant decision of the CoP null and void.
The refusal of a party to comply with an ABMT-decision of the CoP (to which it has not formally objected) taken in violation of the BBNJ Agreement is likely to trigger a dispute concerning the interpretation and application of various provisions of the BBNJ Agreement, including Articles 25(1) and 53 BBNJ Agreement, which oblige parties to implement the BBNJ Agreement and binding decisions of the CoP taken in accordance with it. Accordingly, non-compliant parties face a risk of other parties instituting binding dispute settlement procedures under Part IX of the BBNJ Agreement.Footnote 203 However, there is a range of procedural challenges in the context of disputes concerning contested decisions of international organizations and other bodies with a law-making competence, such as the CoP. These include the lack of competence to annul decisions,Footnote 204 the multiplicity of the parties, and the inter partes effect of decisions of international courts and tribunals.Footnote 205 As a solution to these challenges, attention has been drawn (by reference to existing treaty practiceFootnote 206 ) to the possibility of incorporating advisory opinion mechanisms into the constituent instruments of the respective bodies and to provide for legally binding effects of such advisory opinions.Footnote 207 This would also have been an option for the BBNJ Agreement but apparently was not formally proposed as an alternative to the final wording of Article 47(7) and also does not appear in the Draft Rules of Procedure of the CoP.Footnote 208
7. Conclusions
This article set out to explore how the advisory opinion mechanism in Article 47(7) BBNJ Agreement may contribute to the lawful and effective establishment of ABMTs and MPAs under the BBNJ Agreement, and to analyse the mechanism’s design against the backdrop of existing advisory opinion mechanisms and their increasing relevance in international judicial practice. As a starting point, the reliance of the advisory opinion mechanism on the advisory jurisdiction of the full Tribunal based on Article 21 ITLOS Statute in conjunction with external agreements (and procedurally operationalized by Article 138 ITLOS Rules) has further consolidated ITLOS’s jurisprudence and institutional practice on this matter. In doing so, the BBNJ Agreement contributes to the normalization of the formerly controversial full-bench advisory jurisdiction of ITLOS.
On a conceptual level, the advisory opinion mechanism is well-conceived as it provides the CoP with a possibility to request ITLOS to review the conformity of a (typically ABMT-related) proposal before taking a decision. This ex ante legality assessment can greatly assist the CoP’s decision-making. It informs the CoP on possible legal constraints on its ABMT-competence, such as those in Article 22(2) and (5) BBNJ Agreement. While advisory opinions are non-binding, they hold significant normative and political weight. Their main effect will likely be indirect: influencing the CoP’s legal reasoning, shaping institutional culture, and clarifying complex and controversial questions in the interpretation of the BBNJ Agreement. In some instances, the mechanism could help to prevent unlawful ABMTs from being adopted – thus supporting both the integrity of the BBNJ Agreement and the effectiveness of ABMTs established under it. Relying on an ex ante advisory mechanism rather than ex post contentious dispute settlement also holds advantages such as broader participation in the proceedings (including by IFBs).
However, compared to the advisory opinion mechanisms in Articles 191 and 159(10) UNCLOS, which serve a similar purpose in the context of the ISA, Article 47(7) BBNJ Agreement suffers from a range of features that considerably weaken the advisory opinion mechanism. First, unlike Article 191 UNCLOS, Article 47(7) BBNJ Agreement does not permit requests for advisory opinions ‘on any legal question arising within the scope of [the BBNJ Agreement]’. Instead, Article 47(7) BBNJ Agreement mirrors Article 159(10) UNCLOS insofar as it applies to the conformity of proposals before the CoP with the BBNJ Agreement. The CoP cannot request an advisory opinion in the absence of a proposal, such as on matters of general importance that may arise irrespective of a specific proposal.Footnote 209
Second, the narrow subject-matter scope of the Tribunal’s advisory jurisdiction is further reduced by the three limitations in Article 47(7) BBNJ Agreement which exclude: (i) matters within the competences of other relevant bodies, (ii) implicated disputes concerning sovereignty, and (iii) the status of an area as within national jurisdiction. While reflecting an increasingly cautious approach in jurisprudence and treaty-making, these limitations reduce the Tribunal’s capacity to exercise its advisory function in a manner that fulfils the purpose of a comprehensive ex ante legality review of CoP proposals. Of these limitations, the carve-out for matters within the competence of other relevant bodies may be the most detrimental. The prospectively most pressing questions pertain to the delimitation of competences between the CoP and IFBs and the related interpretation of the obligations to ‘respect the competences of’ and ‘not undermine’. While it is clear that the Tribunal must determine whether a proposal falls within the competence of another relevant body before it declines or accepts advisory jurisdiction over a request, it is less clear if the Tribunal can then proceed to assess the proposal’s conformity with Article 22(2) BBNJ Agreement. ITLOS’s interpretation of the limitation’s scope will be decisive in determining whether its advisory jurisdiction has the potential to make important judicial contributions to inter-institutional legal coherence and coordination. In addition, the limitation to jurisdiction regarding disputes concerning the status of areas as within national jurisdiction may prevent ITLOS from clarifying the applicability of Part III of the BBNJ Agreement in areas like the waters off the coast of Antarctica or the central South China Sea.
Third, an effective ex ante legality control is typically premised upon a possibility for the minority of parties to trigger the relevant process to ensure that the majority of parties does not adopt a decision despite doubts as to its legality. Article 159(10) UNCLOS, which empowers a fourth of the ISA’s members to trigger a request for an advisory opinion of the SDC and a simultaneous deferral of voting on the proposal, is a good example. By contrast, a request under Article 47(7) BBNJ Agreement requires a two-thirds majority – a high threshold that is almost the same as for the adoption of an ABMT-proposal (three-fourths majority, following a decision by a two-thirds majority that all efforts to reach consensus have been exhaustedFootnote 210 ). This means that such requests are only likely if there is either broad agreement in the CoP that a legal clarification is desirable or a sufficiently large number of parties supporting the proposal agree to an advisory opinion request out of goodwill.
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