MarIus

4.2.1 The flag State’s EIA obligation under the BBNJ Agreement

This part of the thesis proceeds on the basis that the EIA regime established under the BBNJ Agreement is best understood as an operational development of the general obligation from Article 206 UNCLOS. As Warwick and Craik observe, Article 27 of the BBNJ Agreement plays an important role by articulating the objectives that underpin the EIA regime, affirming its aim to operationalise Articles 204-206 of UNCLOS through clearer processes, thresholds, and procedural requirements(1)Ibid n30. Articles 27(a) and 27(b) of the BBNJ Agreement link EIAs to State due diligence by framing it as a preventive and evaluative mechanism through which Parties give effect to their obligations of due diligence in respect of activities under their jurisdiction or control that may affect marine biodiversity in ABNJ, a linkage that is subsequently further operationalised through the EIA obligation set out in Article 28. While Article 27 presents the EIA regime under the BBNJ Agreement as giving effect to existing UNCLOS obligations, Warwick and Craik argue that Part IV of the BBNJ Agreement substantively advances beyond Article 206 of UNCLOS by addressing its reliance on subjective and qualified standards through the establishment of more detailed and enforceable procedural requirements (2)Ibid n30. Within this framework, the BBNJ Agreement elaborates the procedural elements of the EIA obligation and emphasises the evaluative role of Parties in determining when potential environmental impacts trigger the obligation to carry out an EIA.

Part IV of the BBNJ Agreement specifies how States are to give effect to their assessment obligation in practice, and it structures the process into successive steps of assessment, consultation, determination, and follow‑up, thereby making the more broadly framed duty under UNCLOS(3)Articles 206 and 211 UNCLOS to conduct EIAs into a more concrete process. An EIA is defined by Article 1(7) as “a process to identify and evaluate the potential impacts of an activity to inform decision-making”(4)Article 1(7) BBNJ Agreement. Tanaka observes that the BBNJ Agreement gives rise to obligations in respect of three forms of environmental assessment, namely, an EIA for activities in ABNJ under Article 28(1), a transboundary EIA under Article 28(2), and the obligation to consider conducting strategic environmental assessments (‘SEAs’) under Article 39(1)(5)Yoshifumi Tanaka, ‘Reflections on the Environmental Impact Assessment in the BBNJ Agreement: Its Implications for the Conservation of Biological Diversity in the Marine Arctic beyond National Jurisdiction’ (2024) 55(1–2) Ocean Development & International Law 85, page 95. For the purposes of this thesis, the analysis is confined to the obligation under Article 28(1).

Article 28(1) of the BBNJ Agreement provides that “Parties shall ensure that the potential impacts on the marine environment of planned activities under their jurisdiction or control that take place in areas beyond national jurisdiction are assessed as set out in this Part before they are authorized”(6)Article 28(1) BBNJ Agreement. The use of the term “shall” makes it clear that Article 28(1) imposes a binding obligation on Parties, under which they are required to ensure that an EIA is undertaken before authorising a planned activity where the other conditions of the article are met.

The first condition set out is that the obligation is limited to planned activities, which emphasises the preventative objective of the BBNJ Agreement, as mentioned earlier in relation to Article 2. Secondly, the activity must fall within the Party’s jurisdiction or control, which anchors the duty to conduct an EIA in the existing State responsibility under the UNCLOS framework. Thirdly, Article 28(1) applies specifically to activities that take place in ABNJ, thereby distinguishing it from the obligation under Article 28(2), which concerns activities taking place within national jurisdiction, but where those activities may nevertheless cause substantial pollution of, or significant and harmful changes to, the marine environment in ABNJ(7)Article 28(2) BBNJ Agreement. Lastly, the obligation to conduct an assessment is triggered where there is an activity that may affect the marine environment; the wording “potential impact” requires only that the activity may have an impact on the environment in ABNJ, which also reflects a precautionary and preventative approach. In this context, scientific uncertainty assumes particular importance for screening decisions, since the preventive logic underpinning due diligence would be undermined if uncertainty was consistently treated as a sufficient reason not to assess potential environmental impacts(8)Ibid n129, page 3. Article 28 does not impose an obligation to achieve a particular environmental outcome, nor does it prescribe the form or content of the assessment. Rather, it requires that EIAs are used as a tool for informed decision-making by Parties, and it provides the foundation upon which the more detailed rules governing the implementation and coordination of EIAs in subsequent provisions, including Article 29, are built.

Draft‑stage commentary by the International Union for Conservation of Nature (‘IUCN’) on the article that later became Article 28 offers a perspective worth mentioning, which suggests that the BBNJ Agreement was conceived as operating under UNCLOS and in the context of existing obligations under the UNCLOS and customary international law such as Pulp Mills(9)International Union for Conservation of Nature (IUCN) World Commission on Environmental Law, IUCN Commentary on the Further Revised Draft Text of an 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 (IUCN, 8 August 2022) 16–18 https://iucn.org/sites/default/files/2022-08/igc5-iucn-commentary-on-bbnj-further-revised-draft.pdf accessed 13.05.2026. While articulated from the perspective of an organisation advocating for an ambitious treaty outcome, this commentary may nonetheless be seen as offering a contextual indication of how the EIA obligation was conceived during the negotiations, and especially its emphasis on early assessment of potential environmental effects as a part of a preventative regulatory approach.

4.2.2 Institutional coherence in the EIA regime under the BBNJ Agreement

The BBNJ Agreement demonstrates a clear concern with institutional coherence through the inclusion of its relationship and non‑undermining clause in Article 5. Pursuant to Article 5(1), the BBNJ Agreement must be interpreted and applied consistently with UNCLOS, while Article 5(2) requires that the BBNJ Agreement is interpreted and applied in a manner that does not undermine “relevant legal instruments and frameworks and relevant global, regional, subregional, and sectoral bodies and that promotes coherence and coordination with those instruments, frameworks and bodies”(10)Article 5(2) BBNJ Agreement. As an implementing agreement adopted under UNCLOS, the existing rights and obligations of Parties are explicitly preserved, and Article 5 establishes that the provisions of the BBNJ Agreement shall not undermine or conflict with other applicable legal obligations. Through its careful wording, the provision underscores the importance of coordination and coexistence with existing sectoral regimes such as the IMO, making it clear that the BBNJ Agreement is intended to complement, rather than displace, other competent legal frameworks and institutions. While the draft‑stage commentary by the IUCN reflects an understanding of the BBNJ Agreement as complementing existing regimes(11)Ibid n188, it has also been noted in the limited literature on the BBNJ Agreement that the precise meaning of the non‑undermining clause remains uncertain, underscoring the interpretive flexibility inherent in its formulation(12)Ekaterina Antsygina, ‘Interpreting the Non‑Undermining Clause of the BBNJ Agreement: Restrictive or Complementary Roles for the COP within RFMO Competences?’ (2024) 28 Max Planck Yearbook of United Nations Law 46.

The inclusion of coordination in Article 5(2) underscores that the BBNJ Agreement cannot be applied in isolation, but must be read in its broader legal context, including UNCLOS, which relies on the regulatory competence of specialised international organisations. In the context of international shipping, that competence is exercised primarily through the IMO. Article 5 is carefully crafted to ensure that the BBNJ Agreement functions as an implementing instrument under UNCLOS, reflecting legal caution aimed at preventing duplication or conflict of obligations and at safeguarding against unintended legal consequences through structured interaction with other relevant frameworks and competent bodies. The operation of EIA obligations under the BBNJ Agreement must therefore be understood as situated within an ongoing and coordinated regulatory environment, rather than as isolated procedural acts detached from the wider law of the sea framework. The terminology “not undermine” has been described scholarly as “deliberately ambiguous”(13)Karen N Scott, ‘Cold Cooperation: Reconciling the Biodiversity Beyond National Jurisdiction Agreement and the Antarctic Treaty System’ (2025) 74(3) International and Comparative Law Quarterly, page 590 but while also pointing out that Article 29 of the BBNJ Agreement provides additional guidance on how the “not undermine” obligation operates in relation to EIAs(14)Ibid n192. From the perspective of this thesis, the ambiguity inherent in Article 5 makes the detailed analysis of Article 29 in the next part of this thesis especially important, as it represents one way in which the BBNJ Agreement seeks to translate general coordination objectives into a legal mechanism in the EIA context.

4.2.3 Article 29: Equivalence assessments as an expression of flag State due diligence

The relationship between the EIA regime under the BBNJ Agreement and existing assessment frameworks must be understood in light of the BBNJ Agreement’s provisions on interaction with other legal instruments and competent bodies. In this respect, Article 5 sets out the general non‑undermining obligation, while Article 29 gives it concrete expression in the context of EIAs. Article 29 governs the relationship between the EIA obligations under the BBNJ Agreement and assessment procedures adopted under other relevant legal instruments and institutional frameworks, setting out when reliance on existing assessments is permissible. In doing so, it gives practical effect to the BBNJ Agreement’s non‑undermining requirement in the context of EIAs.

Rather than functioning as an automatic exemption, Article 29 conditions such reliance on a reasoned determination that the existing assessment is functionally equivalent to the assessment required under Part IV of the BBNJ Agreement. In doing so, Article 29 situates evaluative judgment and due diligence at the centre of flag State responsibility for activities with potential impacts on marine biodiversity in ABNJ. This naturally leads to the question of how to assess equivalency between different assessment processes under different legal frameworks, the scope of State due diligence obligations, and the content of flag State responsibility in this context.

The first issue arising under Article 29 concerns when an environmental assessment undertaken under another legal instrument or framework may be considered as equivalent for the purposes of the EIA regime under the BBNJ Agreement. As mentioned earlier, Article 29 reflects an effort to avoid regulatory duplication by permitting reliance on existing frameworks, where they effectively address the relevant environmental risks, and accordingly adopts a standard of functional equivalence rather than formal identity(15)Nan Jiang, Jiahui Wang and Xin Pan, ‘Implementing the EIA Provisions of the BBNJ Agreement in the International Seabed Area: Obstacles and Recommendations’ (2026) 13 Frontiers in Marine Science 1801291, page 17. Article 29(4) provides that:

“4. It is not necessary to conduct a screening or an environmental impact assessment of a planned activity in areas beyond national jurisdiction, provided that the Party with jurisdiction or control over the planned activity determines:

(a) That the potential impacts of the planned activity or category of activity have been assessed in accordance with the requirements of other relevant legal instruments or frameworks or by relevant global, regional, subregional or sectoral bodies;

(b) That:

(i) the assessment already undertaken for the planned activity is equivalent to the one required under this Part, and the results of the assessment are taken into account; or

(ii) the regulations or standards of the relevant legal instruments or frameworks or relevant global, regional, subregional or sectoral bodies arising from the assessment were designed to prevent, mitigate or manage potential impacts below the threshold for environmental impact assessments under this Part, and they have been complied with” ^{(16)Article 29(4) BBBNJ Agreement}

From the wording of Article 29(4), the question is whether the applicable measures are capable, in practice, of preventing, mitigating, or managing environmental harm below the threshold triggering an EIA under BBNJ Agreement. Rather than focusing on formal characterisation or strict adherence to the procedural architecture of the EIA regime under the BBNJ Agreement, the emphasis is on functional comparability with the Part IV assessment and on the Party’s consideration of its results. The EU, for example, has taken the view that implementation of the BBNJ Agreement would not impose additional burdens on its Member States due to the consistency with existing EU law and other international obligations(17)European Commission, ‘Proposal for a Directive of the European Parliament and of the Council on the conservation and sustainable use of marine biological diversity of areas beyond national jurisdiction’ (24.04.2025) 2025/0090 (COD), page 3, https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:52025PC0173 accessed the 12.04.2026, thereby reflecting an understanding of the BBNJ Agreement as systematising and coordinating existing assessment obligations rather than displacing them.

Article 29(4) establishes a conditional framework under which a Party can determine that a separate EIA under the BBNJ Agreement is not required, provided that the relevant requirements from Article 29(4) are met. Article 29(4) has been described as an ambiguous equivalence exception(18)Neil Craik and Karen Scott.: ‘Environmental Impact Assessment under the Biodiversity Beyond National Jurisdiction Agreement and the Equivalence Exception’, One Ocean Science Congress 2025, conference paper (3–6 Jun 2025), OOS2025-713, https://doi.org/10.5194/oos2025-713 accessed the 12.04.2026., and the difficulty with the equivalence exception lies in the fact that equivalence is not a binary concept but instead exists along a spectrum(19)Ibid n197. Determining whether an existing process is equivalent therefore requires evaluative judgment as to alignment in purpose, scope, and effect. Equivalence in this case means being comparable in effect, not necessarily identical in form. Although developed in the context of seabed mining as an activity in the ABNJ, concerns have been raised about the absence of a clear equivalence standard and that independent oversight may enable unilateral State self‑assessment and forum‑shopping, potentially undermining the environmental integrity of the regime under the BBNJ Agreement(20)Ibid n194, page 11. These broader coordination issues may also be relevant for other sectoral regimes subject to the EIA regime under the BBNJ Agreement, and similar concerns may arise as to how reliance on IMO‑based regulatory and risk‑assessment frameworks may satisfy the equivalence requirements of Article 29 in the shipping context.

In accordance with Article 31 of the VCLT, Article 29(4) must therefore be interpreted in good faith in light of the ordinary meaning of its terms and the object and purpose of the BBNJ Agreement. This interpretive framework therefore supports a reading of ‘equivalence’ that gives practical effect to both environmental protection and regulatory coordination. Scholarly commentary has cautioned that an overly restrictive understanding of equivalence can result in a scenario where only assessment procedures that mirror the BBNJ Agreement’s provision in almost all respects would qualify and that this can result in unnecessary duplication or inconsistent outcomes at risk of undermining the environmental objectives of the BBNJ Agreement(21)Ibid n197. On the other hand, an interpretation of equivalence that is too generous can end up making the EIA process under the BBNJ Agreement redundant(22)Ibid n197, enabling reliance on prior assessments without sufficient scrutiny. The discussion now proceeds to address the conditions attached to the equivalence exception in Article 29(4). A comprehensive assessment of equivalence as an independent concept in the BBNJ Agreement is beyond the scope of this thesis but represents an area meriting more extensive analysis in future research.

Article 29(4) does not remove the obligation on Parties to assess the impacts on the environment simply because some form of assessment has already taken place under another legal regime. Article 29(4)(a) requires that Parties must determine that the potential impacts of the planned activity have already been assessed in accordance with the requirements of other relevant legal instruments, frameworks, or processes, such as under the EU Environmental Impact Assessment Directive (2011/92/EU, amended by 2014/52/EU). Article 29(4)(a) therefore has a gatekeeping function - while it does not in itself exempt a Party from conducting an EIA in accordance with the regime under the BBNJ Agreement, it conditions access to the exemption mechanism available through Article 29(4)(b).

If an assessment has taken place in accordance with the requirements of a relevant legal instrument or framework other than the BBNJ Agreement, then Article 29(4)(b) sets out two ways to exempt a Party from conducting a new EIA under the BBNJ Agreement. Under subparagraph (b)(i), the prior assessment is assessed to be equivalent to that required under Part IV of the BBNJ Agreement and its results have been taken into account(23)Article 29(4)(b)(i) BBNJ Agreement. Under subparagraph (b)(ii) on the other hand, reliance is instead placed on regulations or standards arising from the prior assessment that has taken place, provided that the regulations or standards were designed to prevent, mitigate, or manage impacts from below the EIA threshold from the BBNJ Agreement and the regulations or standards have been complied with(24)Article 29(4)(b)(ii) BBNJ Agreement. When read together, in principle, Article 29(4) permits reliance on substantively effective regimes while maintaining the BBNJ Agreement’s EIA obligation as a backstop where they are insufficient – and Article 29 can also be understood to implicitly require States to undertake a sort of substantive benchmarking assessment of “equivalence” when having to determine whether reliance on an existing assessment is justified. Such a determination is not a procedural formality, but rather a determination of whether the existing assessment, benchmarked against the requirements and objectives of the BBNJ Agreement, is capable in substance and effect of meeting its environmental aims. A similar preventive understanding underpins the reasoning of the ICJ in the Pulp Mills case, in which the Court emphasised that the duty to assess environmental impacts arises once a potential risk of significant transboundary harm can be identified, and that such assessment must be carried out before a decision is made to authorise the activity(25)Ibid n104, Pulp Mills, paragraph 204.

It can be argued that Article 29(4) reinforces, rather than relaxes, the State’s due diligence obligation by transforming reliance on existing assessments from a permission into a responsibility. A Party that relies on an existing assessment without adequately examining its scope, quality, or effectiveness in addressing impacts on biodiversity in ABNJ risks falling short of its duty to ensure that activities under its jurisdiction or control are properly assessed. This thesis therefore finds that the equivalence determination required under Article 29 constitutes a central element of the due diligence owed by State Parties under the BBNJ Agreement and is of relevance for flag States in assessing activities carried out by vessels flying their flag in ABNJ. Where a State Party permits an activity to proceed without conducting a separate EIA under the BBNJ Agreement based on an existing assessment, due diligence is reflected in the way that the State Party has examined and come to the decision to support reliance on the existing assessment.

This argumentation is in line with how ITLOS defines due diligence as an obligation of conduct, not of result (26)Ibid n104, SRFC advisory, paragraphs 125-131. For the purposes of this thesis, with respect to marine biodiversity in the ABNJ, a flag State is therefore not subject to an obligation of result requiring it to guarantee that all activities carried out by vessels flying its flag fully comply with applicable environmental requirements. Rather, the flag State is required to exercise due diligence by taking reasonable and appropriate measures to ensure that potential impacts are properly identified and assessed before an activity is authorised. In the COSIS Advisory Opinion, ITLOS further confirms that “activities carried out on board ships or aircraft which are registered in a State may be considered activities under the jurisdiction of that State”(27)Ibid n59, paragraphs 247, 360–361, thereby supporting the view that vessel‑based activities in ABNJ can fall within the notion of “activities under their jurisdiction or control”(28)Article 194(2) UNCLOS as defined in Article 194(2) of UNCLOS. Article 29 accordingly functions as a conditional gateway rather than a blanket exemption, limiting State Party discretion by conditioning reliance on existing frameworks to a reasoned and defensible benchmarking of equivalence, rather than to the formal existence of prior regulatory processes.

This understanding gives rise to a further question: on what basis may a State Party legitimately rely on an environmental assessment conducted under another body/legal framework for the purposes of compliance with its EIA obligations under the BBNJ Agreement? The BBNJ Agreement does not specify which bodies’ assessments may be relied upon, nor does it provide guidance as to why reliance may be justified in some cases but not in others(29)Article 29(4) BBNJ Agreement. It is in this context that a capacity‑based criterion has been mentioned as a relevant means of giving effect to the coordination logic from Article 5(30)Alla Pozdnakova, ‘The IMO and Treaties: Appraisal of the IMO’s Contribution to Future Ocean Governance’ in Laura Carballo Piñeiro and Máximo Q Mejia Jr (eds), The Elgar Companion to the Law and Practice of the International Maritime Organization (Edward Elgar Publishing 2024) 86, page 19. Scholarly commentary has suggested that the primary consideration when assessing an entity’s role within the BBNJ Agreement’s institutional framework should be its ability to meet the BBNJ Agreement’s objectives(31)Ibid n209. In that sense, capacity is context-specific and depends on factors such as a body’s mandate and powers, its sectoral focus, its geographic reach, and its practical implementation record(32)Ibid n209. Accordingly, the BBNJ Agreement’s implications for existing organisations are difficult to generalise and it has been suggested that the interplay between the organizations might need to be assessed case by case(33)Ibid n209. Such a capacity-based approach is found to be persuasive: it offers a principled basis for differentiating among institutions, and as pointed out by Pozdnakova, it avoids assuming that all existing bodies are similarly situated(34)Ibid n209.

Read together with the non‑undermining requirement in Article 5, this supports a model of interaction in which reliance on existing frameworks is neither automatic nor excluded in principle, but contingent on their demonstrated capacity to contribute meaningfully to the protection of marine biodiversity in ABNJ. In this sense, the EIA regime under the BBNJ Agreement operates as part of an integrated and coordinated regulatory environment, rather than as a self‑contained procedural layer.