The high seas and the deep seabed comprise nearly two-thirds of the world’s ocean.  Historically, the use of high seas was characterised by the principle of freedom.  This principle was designed to prevent undue interference from the States that sought to establish sovereignty over the oceans.   

Following decades of negotiations and as part of COP 15 (during which the Kunming-Montreal Global Biodiversity Framework was adopted), States have reached an agreement to protect the world’s oceans’ marine biological diversity of areas beyond their national jurisdictions.  This agreement is the Biodiversity Beyond National Jurisdiction treaty (the “BBNJ Agreement” or the “High Seas Treaty”). In terms of the “areas beyond national jurisdiction” (the high seas), the UN General Assembly had previously established, in 2004, an ad hoc, open-ended Informal Working Group to address the conservation and sustainable use of marine biodiversity in those areas. In 2017, it organised the first of several intergovernmental conferences to develop the text of a treaty under the United Nations Convention on the Law of the Sea (“UNCLOS”). Eventually, the text of the High Seas Treaty, the third implementing agreement under UNCLOS, was agreed on 5 March 2023. 

This agreement marks an important milestone in the protection of marine species. According to the International Union for Conservation of Nature (“IUCN”) nearly 10% were found to be at risk of extinction. Although it will only enter into force 120 days after the sixtieth instrument of ratification, approval, acceptance or accession, it is expected that some States may begin to implement national legislation to pursue its objectives in advance. It is also possible for States to apply its provisions on a provisional basis. Indeed, in December 2022, States decided to pursue a target of achieving effective protection and conservation for 30% of the ocean by 2030. 


Main Areas of Focus 

The High Seas Treaty focuses upon four key areas: 

  1. Part II focuses on “marine genetic resources, including the fair and equitable sharing of benefits”. Such resources are taking on an ever-increasing significance, given their potential use in developing medicinal and other products. Under the High Seas Treaty, activities relating to marine genetic resources are expressly agreed to be “for the benefit of all humanity” (Article 9(5)), and the benefits arising from these activities have to be shared fairly and equitably between States (Article 7(a)). Planned activities regarding collection of marine genetic resources must be referred to a “clearing-house mechanism determined under article 51” (Article 9(3)), which is centrally-managed by a newly-established Secretariat; 
  2. Part III focuses on “measures such as area-based management tools, including marine protected areas”. Proposals for establishing area-based management tools are to be submitted to the Secretariat. Such measures are designed to restrict certain human activities in certain areas marked for conservation purposes. Under Article 17(2), States are required to consult with “relevant stakeholders” and a range of specific groups, including “the scientific community” and “Indigenous Peoples”; 
  3. Part IV focuses on “environmental impact assessments”. It requires pre-authorisation assessments of the potential impacts of planned activities on the high seas or deep seabed. States are required to ensure that environmental impact assessments are conducted for planned activities within their “jurisdiction or control” (although these terms are not defined). Detailed provisions are set out in Part IV prescribing the process by which environmental impact assessments are to be conducted; and 
  4. Part V focuses on “capacity-building and the transfer of marine technology”. States are required to cooperate to assist each other in achieving the High Seas Treaty’s objectives. A special fund is established by Article 52 to enable developing States to be financially assisted with implementing the High Seas Treaty (both States and private entities may make contributions to the special fund). 


General Principles/Approaches 

The general principles and approaches are set out in Article 5. They offer guidelines for States’ implementation of the High Seas Treaty’s objectives. These include “the polluter-pays principle”, the “principle of equity, and the fair and equitable sharing of benefits”, the precautionary principle/approach, an ecosystem approach, an integrated approach to ocean management, and “full recognition of the special circumstances of small island developing States and of least developed countries”. 

Notwithstanding some criticism as to their lack of specificity on occasion (for example, the UN General Assembly recognised in 2006 that there was no universally agreed definition of the “ecosystem approach” in international law, and the UN Convention on Biological Diversity’s inclusion of “fair and equitable benefit-sharing” as one of its objectives without defining either “fair” or “equitable” was considered unsatisfactory in some quarters), these principles are generally well established in other international law instruments that refer to global environmental protection. For example, the principle of intergenerational fairness recognizes for each generation the right to use and enjoy natural resources together with a corresponding duty to conserve these resources for the future for future generations. 


The Practical Aspects 

The High Seas Treaty establishes several important new institutions to deal with operational aspects. These include: 

  1. a Conference of the Parties (“COP”), established under Article 48, which is responsible, inter alia, for adopting “decisions and recommendations related to the implementation of [the High Seas Treaty]” (Article 48(5)), and can take emergency decisions in response to natural phenomena or human-caused disasters (Article 20 ante). Several important issues are deferred by the High Seas Treaty to the COP, such as: the establishment of area-based management tools (including marine protected areas), the practical aspects of how monetary benefits from marine genetic resources are to be shared and how the clearing-house mechanism will work practically; 
  2. a Scientific and Technical Body, established under Article 49, inter alia, to provide advice to the COP; 
  3. a Secretariat, established under Article 50, inter alia, to provide administrative and logistical support to the COP and other bodies; 
  4. an Implementation and Compliance Committee, established by Article 53 ter, inter alia, to assess States’ compliance with the High Seas Treaty; and  
  5. a Clearing-House Mechanism, established under Article 51, which provides for an open-access, centralized platform to disseminate information on activities taking place pursuant to the High Seas Treaty. 


Existing Rights and Obligations 

By virtue of Article 63, signatories to the High Seas Treaty are not permitted to enter any reservations or exceptions beyond those reservations expressly provided for in the treaty itself. 

States’ existing rights and obligations under UNCLOS are expressly not affected by the High Seas Treaty’s provisions (Article 4(1)). The High Seas Treaty also is required to be applied consistently with existing conventions that address areas beyond national jurisdiction (such as the Ospar Convention, which regulated international cooperation on environmental protection in the North-East Atlantic).   



There is, quite obviously, overwhelming public interest in ensuring that the High Seas Treaty is implemented and operated successfully. The High Seas Treaty puts a mechanism in place to deal with disputes in an effective manner. Article 55(1) provides for the settlement of disputes in accordance with “Part XV of [UNCLOS]”, unless another mechanism is accepted (See, Article 55(2)). There are at time of writing 168 parties to UNCLOS, and non-parties to UNCLOS are enabled by Article 55(4) to accept by written declaration one or more of the dispute resolution mechanisms available under UNCLOS (including an arbitral tribunal, a special arbitral tribunal, ITLOS and the ICJ). Article 288 of UNCLOS provides that a tribunal constituted under UNCLOS shall have jurisdiction over any matter concerning the interpretation or application of UNCLOS or an international agreement related to the purposes of UNCLOS. Disputes on technical matters are referable to “an ad hoc expert panel” (Article 54 ter). 

Under Article 48(6), the COP is empowered to request advisory opinions from the International Tribunal for the Law of the Sea (“ITLOS”) “on a legal question on the conformity with this Agreement of a proposal before the [COP] on any matter within its competence”. Given the wide range of matters that the COP is concerned with, this is likely to mean that many disputes or disagreements, including on important areas, such as the area-based management tools (including marine protected areas), may be resolved through narrowly-defined questions referred for an advisory opinion than through contentious proceedings.  

Furthermore, there are several carve-outs to the COP’s power to request an advisory opinion:  

A request for an advisory opinion shall not be sought on a matter within the competence of other global, regional, subregional or sectoral bodies, or 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, or the legal status of an area as within national jurisdiction”.  

The carve-outs demonstrate a concern on the part of States to ensure that contentious disputes are not referred to ITLOS as ‘advisory opinions in disguise’. Nevertheless, the advisory functions of the ICJ and ITLOS have proved effective in providing authoritative guidance (including on an urgent basis) on important international law matters. ITLOS, in particular, has been a valuable mechanism for delineating the rights and responsibilities of States on maritime environmental matters. For example, in Responsibility and Obligations of States with respect to Activities in the Area, the Seabed Disputes Chamber of ITLOS rendered a unanimous advisory opinion on 1 February 2011 on questions pertaining to the legal responsibilities and obligations of States Parties to UNCLOS regarding sponsorship of activities in the seabed area beyond national jurisdiction, and the extent of liability of a State Party for failure by an entity it has sponsored to comply with UNCLOS provisions. 


Concluding Remarks 

Whilst the High Seas Treaty is undoubtedly a major step towards the goal of ensuring maritime biodiversity in areas beyond national jurisdiction is adequately and effectively protected, the treaty faces considerable challenges that must be overcome before it is fully implemented and its intended benefits reaped. Many of these challenges are ones rooted in the political will necessary to achieve the 60 instruments needed to bring the High Seas Treaty into full force. As ever, the success of laudable major international agreements is dependent upon the intentions and actions of those at a national level. Time will tell whether the High Seas Treaty’s provisions will lead to effective protection for the high seas and the seabed, and whether additional guidance will be needed from bodies such as ITLOS before that can be achieved in practice. 


N.B.: At the time of writing, the version of the High Seas Treaty available publicly is expressly labelled “advanced, unedited, pending paragraph renumbering”. The article numbers given in this article may be subject to further revision.  


Joseph Dyke is a Senior Associate at McNair International, specialising in commercial litigation, international arbitration and public international law. He has assisted on international investment and commercial arbitrations under the auspices of several leading arbitration institutions, including LCIA/ICC/SIAC, and ad hoc arbitrations under UNCITRAL Rules. In addition, he has assisted with court proceedings related to challenges against and enforcement of arbitral awards, and Public International Law matters, including before the International Court of Justice. You may contact Joseph 

Anastasia Medvedskaya is an Associate at McNair International. She specialises in international commercial and investment arbitration and public international law.  She has acted as counsel for investors and States in several investment treaty disputes and in commercial arbitration cases under the ICSID, ICC, LCIA, and UNCITRAL rules. Prior to joining private practice Anastasia worked with EY Paris working alongside damages experts. You may contact Anastasia