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Although not a judgement per se and lacking binding force, as explicitly pointed out by the Tribunal, yesterday’s Advisory Opinion by the #Tribunal for the Law of the Sea marks another corner stone in international climate litigation.

Text of the Advisory Opinion can be found here.


The International Tribunal, an independent judicial body established by the Law of the Sea Convention in 1982, has its seat in Hamburg. Within its jurisdiction which covers any dispute concerning the interpretation and application of the Convention and over all matters specifically provided for in any agreement which confers jurisdiction of the Tribunal, it grasped the opportunity to take a stance for climate protection within the Convention.

The Advisory Opinion had been requested by the “Commission of Small Island States on Climate Change and International Law” (#COSIS), a Commission composed of small island states founded in 2021 with the purpose of counteracting climate change and protecting and preserving the marine environment by promotion and contribution to the development of international rules and standards.

Small island states are typically more vulnerable to the negative impacts of climate change. Rising sea levels and loss of biodiversity through marine pollution constitute existential threats to both their territory and way of life. This specific vulnerability of island inhabitants was subject to and confirmed by another decision on the adverse impacts on climate change by the UN Human Rights Committee in September 2022 (CCPR/C/135/D/3624/2019 – Link).  

In line with their purpose, #COSIS posed before the Tribunal the following two-part questions regarding the obligations of Signatory States of the Law of the Sea Convention in regards to marine pollution by #anthropogenicclimatechange:

What are the specific obligations of State Parties to the United Nations Convention on the Law of the Sea (‘UNCLOS’), including under Part XII:

  • to prevent, reduce and control pollution of the marine environment in relation to the deleterious effects that result or are likely to result from climate change, including through ocean warming and sea level rise, and ocean acidification, which are caused by anthropogenic greenhouse gas emissions into the atmosphere?
  • to protect and preserve the marine environment in relation to climate change impacts, including ocean warming and sea level rise, and ocean acidification?

The Tribunal’s response to the request, did not disappoint.

Though the questions were interpreted not to include the ever-contentious questions of responsibility and liability of the State Parties, the obligations arising from the Convention were mapped out in great detail and parallels were drawn to international agreements on Climate Change such as the Paris Agreement.

In fact, the Tribunal found, that the Paris Agreement inter alia serves as a source of interpretation for the relevant provisions of the Convention in relation to pollution of the marine environment and the State Parties obligations to that end. While it is typical that Courts and Tribunals draw upon the Paris Agreement as a guideline for the interpretation of climate mitigation and protection measures in Climate litigation cases, it is what followed that makes this Advisory Opinion stand out:

In the context of Article 194 which contains the obligation of State Parties to individually and jointly take “necessary measures” to prevent, reduce and control pollution of the maritime environment and was identified by the Tribunal as a key provision for the Advisory Opinion, the Tribunal took a closer look at the definition of the legal term “necessary measures”. The influence of the UNFCCC and the Paris Agreement on this proved to be a contentious subject in the Tribunal. But the majority of the Tribunal finally found that the UNFCCC and the Paris Agreement can be drawn upon to interpret the meaning and extend of the “necessity” in each individual case, particularly regarding temperature goal and timeline for emission pathways as set out in the Paris Agreement.

However, highlighting the independence and divergent purposes of the two legal constructs, the Tribunal did not find the Paris Agreement to be lex specialis to the Convention. In light of that it found that obligations under the Convention are not modified or limited by the Paris Agreement and cannot be satisfied by the State Parties simply by complying with obligations and commitments under the Paris Agreement. Though the Tribunal avoided such an explicit statement that finding seems to encompass the view that in parts the obligations under the Convention supersede the Paris Agreement which is quite groundbreaking.

Some key findings of the Tribunal:

Opening up the scope of the Convention and thus surely paving the way for much marine environment litigation to come is the Tribunal’s finding that anthropogenic GHG emissions fall under the definition of pollution in Art. 1 (1) (4) of the Convention. The three cumulative requirements set out therein are fulfilled: I. Introduction by man, II. of substance or energy to the marine environment, III. likely to cause deleterious effects as harm to living resources and marine life. Taking recourse to findings of the #IPCC reports the Tribunal found that Greenhouse gases are increasingly produced by human activity. CO2 which is a major source of #GHG is in large part taken up by the ocean and dissolved in sea water leading to disastrous effects for the marine environment such as ocean warming, sea level rise and ocean acidification.

Next the Tribunal identified a handful obligations of conduct for the State Parties contained in various provision of the Convention such as Article 194 (as described above) and Section 5 of Part XII of the Convention for specific sources of pollution.

Though the Tribunal recognized that the obligations of conduct do not impose on State Parties an obligation to take necessary measures for prevention, protection and control of the pollution of the marine environment at all time but to conduct themselves with due diligence. The standard of conduct found appropriate and the applicable criteria in that context, increase the pressure on State Parties to ensure protection, prevention and control of pollution to the marine environment.

The Tribunal took a broad understanding of the obligation to protect which includes both mitigation and prevention of harm as well as restoration and conservation as it is scientifically proven that there’re already lasting detrimental effects of #GHG emissions to the marine environment. It also recognized the ongoing scientific findings and scientific uncertainty that characterizes global climate change which in turn was found not to provide an excuse for inaction by the State Parties; -instead, a precautionary approach must be applied.

Generally State Parties must consider four factors when developing necessary measures, regional and international laws, standards and regulations: 1. Best Scientific Evidence 2. Precautionary Approach and 3. Environmental Impact Assessment

Another factor carefully taken into account by the Tribunal regarding the diligent standard of conduct by State Parties, was varying capabilities and available means of each State Party. Here the Tribunal established a rule of thumb which reappeared later in the Advisory Opinion:

States with greater means must do more than states with less means. The principle of Common but Differentiated Responsibilities and Respective Capabilities (#CBDR-RC) must be considered and applied.

The obligation of technical assistance for developing states (Articles 202, 203) is also in line with this principle. In recognizing the unequivocal distribution of the burden of climate change globally, the obligation for technical assistance imposes on capable and developed states an obligation of support in capacity building, technical development and transfer and financial support. Though this assistance was deemed to be limited to the specific aim of the protection and preservation of the marine environment and the prevention, reduction and control of marine pollution.

Finally, the Tribunal described two obligations that could be described as framework obligations, the #obligation of enforcement which obligates State Parties to enforce regional and international laws and regulation and to adopt laws and measures necessary to implement international rules. And, the #obligation to cooperate which entails the cooperation with other State Parties on formulating and establishing international rules, studies and research programs and scientific criteria and on ensuring that pollution of maritime environment is properly acknowledged.


Through this Advisory Opinion the Tribunal for the Law of the Sea created for themselves a new case load. NGOs and climate litigators are likely to leverage this opportunity to create binding precedents for climate action. The Tribunal should be prepared for an influx of cases aimed at shaping the future of environmental jurisprudence.