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15 November 202318 minute read

Climate Change in the Spotlight

The Advisory Opinion Proceedings of the International Courts

Speaking at the opening of the 2024 Climate Ambition Summit, UN Secretary-General, António Guterres stated that “[h]umanity has opened the gates to hell” by allowing the climate crisis to worsen.1  Climate change is the defining issue of our time. Our ability to mitigate and adapt to the effects of climate change is crucial to the protection of our planet for both present and future generations. The international community, being acutely aware of these impacts, has applied to two of the highest global authorities for historic advisory opinions on States’ obligations in respect of climate change resulting from anthropogenic greenhouse gas emissions.

The first of the advisory proceedings in September 2023, heard by the International Tribunal for the Law of the Sea (ITLOS or the Tribunal) at its home in Hamburg, sought to clarify States’ obligations to protect the marine environment from the adverse effects of climate change caused by anthropogenic greenhouse gas emissions. The ITLOS advisory opinion is a precursor to the much wider and more significant advisory proceedings, in scope, likely participation and authority, that are set to take place before the International Court of Justice (ICJ or the Court) at The Hague in 2024.

The ICJ has been asked to clarify States’ general obligations under international law in response to climate change caused by anthropogenic greenhouse gas emissions. There are also related advisory proceedings before the Inter-American Court of Human Rights and contentious proceedings before the European Court of Human Rights relating to climate change and the human rights obligations of States.

These cases will:

  • be highly persuasive in defining the rights and obligations of States, as concerns State action and/or inaction, to protect the environment from the effects of anthropogenic greenhouse gas emissions;
  • likely increase the risk of claims whether between States and foreign investors in international tribunals (by virtue of a State’s adoption of more robust climate legislation), against governments and companies in domestic courts (by virtue of the persuasive nature of international law), or at a State-to-State level in international courts and tribunals (likely pursued by smaller impacted coastal States against high emitting States);
  • be highly relevant to the increasing pressure on high emitting States to seek diplomatic outcomes, including future COP agreements: and
  • add to the pressure on States to tighten domestic regulatory pressure on all matters carbon related.

It is clear that the adverse effects of climate change on both present and future generations has reached a tipping point for developed and developing States. As States Parties collectively recognised at COP27 in 2022, “Parties are not collectively on track to achieve the long-term global goal and that the pre-2020 pledges of some Parties and their subsequent implementation have been insufficient.”  The collective action from States to clarify their obligations under international law in respect of climate change shows clear momentum to evaluate the global response to climate change. These advisory opinions are the most important pieces of climate change litigation of our time, and have the potential to seriously influence States’ actions required to achieve the 1.5°C temperature goal set in the Paris Agreement.

This article seeks to provide a high-level overview of the ITLOS and ICJ advisory opinion proceedings and considers the potential implications of each at both international and domestic levels.


What is an advisory opinion?

Advisory opinion proceedings, as distinct from contentious proceedings, are where a tribunal or court gives an opinion on legal questions referred to it by authorised bodies. For example, the ICJ can only deliver an advisory opinion in response to a referral from the United Nations General Assembly, the United Nations Security Council, or other United Nations organs and specialised agencies authorised by the General Assembly. States are invited to make written and oral statements on the question put to the tribunal or court to help inform its conclusions. Advisory opinions are not binding on States but may be considered highly persuasive and carry great legal weight.

The questions posed to ITLOS and the ICJ in these advisory proceedings concern only the obligations of States. Therefore, any findings made by ITLOS or the ICJ are not expected to have direct and immediate impacts on corporate entities.


International Tribunal for the Law of the Sea Climate Change Advisory Opinion

What was the question put to the tribunal?

On 12 December 2022, the Tribunal received a request from the Commission of Small Island States on Climate Change and International Law, comprising of Antigua and Barbuda, Niue, Palau, Saint Lucia, Tuvalu and Vanuatu (COSIS) to render an advisory opinion. Per the COSIS Agreement, COSIS’s mandate is “to promote and contribute to the definition, implementation, and progressive development of rules and principles of international law concerning climate change”.

COSIS referred the following questions to ITLOS for an advisory opinion:

What are the specific obligations of State Parties to the United Nations Convention of the Law of the Sea (UNCLOS), including 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?

From 11 to 25 September 2023, the 21 Members of the Tribunal heard oral arguments from 35 States Parties to UNCLOS and three intergovernmental organisations. This was in addition to the written submissions received from 34 States Parties and nine intergovernmental organisations. A further 10 statements from various international bodies were filed.

While 43 participants may not seem a large grouping, a total of 45 States and four international organisations made written statements in the 2004 ICJ advisory opinion on the Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory – being the former advisory opinion proceeding with the highest engagement. It is clear from the turn out at ITLOS that climate change sits high on the agenda of the international community.

What were the arguments states made?

As a threshold issue, the overwhelming majority of States argued that anthropogenic greenhouse gas emissions fall within the definition of “pollution of the marine environment” under Article 1(1)(4) of UNCLOS. This is important as an expanded definition empowers the Tribunal to consider causal links between such emissions and impacts on the marine environment.

In terms of substantive obligations, two UNCLOS provisions formed the foundation of almost every States’ submission, being Articles 192 and 194 of UNCLOS. Article 192 imposes a general obligation on States to protect and preserve the marine environment. Article 194 requires States to take all measures necessary to prevent, reduce, and control pollution of the marine environment from any source, using the best practicable means at their disposal. Several States also made submissions on whether the “duty to cooperate” forms part of States Parties’ obligations under UNCLOS, and the extent of the operation of the principle “common but differentiated responsibilities” (being a shared responsibility to respond to climate change where the nature of obligations imposed are influenced by a State’s respective capabilities and level of development).

While all States considered the role of Articles 192 and 194 in their submissions, three groups of arguments formed:

  1. COSIS’s position – States’ obligations in UNCLOS should be read to include the 1.5°C temperature goal agreed to in the Paris Agreement
    • COSIS took a firm position on the content of States’ obligations regarding emissions reduction and protection of the marine environment. COSIS argued that Articles 192 and 194 of UNCLOS impose clear and specific obligations on States to take action in response to climate change, including an obligation to take all necessary measures aimed at reducing greenhouse gas emissions from all sources to limit the average global temperature rise to 1.5°C. COSIS’s argument essentially sought to have States’ specific legal obligations under UNCLOS be read to include the 1.5 °C temperature goal in Article 2 of the Paris Agreement:
    • Holding the increase in global average temperature to well below 2 °C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels…”
    • COSIS submitted that States may be required to go further than commitments made in the Paris Agreement (and other climate change treaties) in order to comply with their obligations under UNCLOS.

  2. Middle position – States’ obligations under UNCLOS should be read in light of / informed by commitments made under climate change treaties
    • This category of States recognised that where there are multiple obligations that relate to a single issue, these obligations should be, to the extent possible, interpreted in a way to give rise to a single set of compatible obligations. On that basis, States’ obligations under UNCLOS should be read in light of commitments made in later treaties such as the United Nations Framework Convention on Climate Change (UNFCCC) and the Paris Agreement. States in this category stopped short of suggesting that the obligations in the UNFCCC and Paris Agreement could be imported to circumscribe States’ obligations under UNCLOS. Some States further recognised that environmental obligations under UNCLOS may go beyond those contained in the UNFCCC and the Paris Agreement.

  3. Hard line against COSIS position – States’ obligations under UNCLOS and the climate change treaties are separate
    • A number of States adopted a position in direct contrast with COSIS. These States argued the climate change treaties (e.g., the UNFCCC and the Paris Agreement) constitute a specialised regime to regulate greenhouse gas emissions. On that basis, compliance with those agreements should mean compliance with States’ obligations under UNCLOS to protect and preserve the marine environment from the effects of anthropogenic greenhouse gas emissions. These States were clear that non-binding commitments made under the climate change treaties, namely commitments to the goal of limiting global temperature increase to well below 2°C, should not be imported into UNCLOS as specific legal obligations on States.

What comes next?

The Tribunal is anticipated to deliver its advisory opinion in the first half of 2024, after written statements are filed in the upcoming ICJ proceedings.

The ICJ has set 22 January 2024 as the deadline for States and authorised organisations to submit their written statements, with 22 April 2024 as the deadline to respond to other States’ and authorised organisations’ statements. The dates for the oral hearings are yet to be set down.

Importantly, there are two major differences between the ITLOS and the ICJ proceedings:

  • The ICJ proceedings are much broader in scope – while the ITLOS proceedings were limited to the interpretation of UNCLOS, the ICJ has been asked to consider its question in light of general international law, including obligations under international human rights law and multilateral treaties on biological diversity.
  • The question before the ICJ considers the legal consequences under international law – the questions before ITLOS did not contemplate the legal consequences for potential breaches of States’ obligations, and submissions were made by States to reinforce that such consideration would be outside the scope of the Tribunal’s advisory competence in the proceedings.


Relevance of Advisory Opinion Proceedings at International and Domestic Levels

The advisory opinions are likely to have a series of direct and indirect effects on both States, private corporations, and individuals.

Empowering states to pursue more robust climate legislation and nationally determined contributions

National laws and regulations play a crucial role in the implementation of States’ international obligations. All 193 Parties (192 countries plus the European Union) that have joined the Paris Agreement have introduced at least one law addressing climate change or the transition to a low-carbon economy.2

The content of the advisory opinions may then serve as a basis for strengthening domestic legislative frameworks. Potential State responses may include legislating an emissions reduction target, banning or limiting the development of fossil fuel projects, offering economic incentives to shift demand to sustainable solutions, or submitting a revised Nationally Determined Contribution that sets more stringent emissions reduction.

Potential for increase in investor claims under investment treaties

State adoption of more robust climate legislation may, however, increase the risk of potential claims from foreign investors under bilateral and multilateral investment treaties. Such risks have already been realised by Contracting Parties of the Energy Charter Treaty (ECT), whereby approximately 150 investment arbitration cases have been instituted by or against Contracting Parties to date (sometimes invoked alongside a bilateral investment treaty). Resultantly, as of the date of publication, France, Germany, Luxembourg and Poland have formally notified their withdrawal from the ECT, with other States having commenced the withdrawal process (including Spain and the Netherlands) or otherwise indicating an intention to do so.

In another example outside of the ECT, earlier this year, Canada faced an investor claim by Westmoreland Mining Holdings LLC (Westmoreland) brought under the North American Free Trade Agreement. Westmoreland alleged that the Province of Alberta’s Climate Leadership Plan (CLP), which sought to phase out all electricity generated from coal by 2030, had reduced the lifespan of Westmoreland’s mines in Alberta and treated the claimant unfairly. Westmoreland further alleged that Alberta had treated it unfairly and in a discriminatory manner by providing transition payments to three coal-fired generating unit owners impacted by the CLP, and not providing such a payment to the claimant for its coal mine assets.3

Interestingly, Sierra Leone, in its oral arguments before ITLOS, made submissions on the interaction of the advisory opinions with investment treaties and investor claims. Sierra Leone argued that under UNCLOS, there is a wide “margin of appreciation” enjoyed by States to regulate in the public interest, including with respect to the protection and preservation of the environment. The argument ran that States have the right to decide the domestic measures to be taken to limit temperature rise in line with their international obligations. Arguably, without recognising such a right, States will be disincentivised from taking actions required to address emissions reduction for fear of being subject to an investor-State claim.4

Outside of investor-State claims, some commentators have also observed that the advisory opinions may be used as a basis to commence contentious cases against high emitting or high polluting States and corporations. Such risks may be considered an undesirable consequence for States.

Relying on the advisory opinion findings in domestic court proceedings

The Tribunal and the Court have been asked to make findings that concern sovereign States – neither has been asked to opine on the actions of corporations or individuals. Whilst States ultimately hold the obligations under international law in respect of climate change, corporations and individuals may be subject to national legislation requiring action with regard to greenhouse gas emissions, in implementation of a State’s obligation. The Tribunal’s or the Court’s findings could therefore empower domestic courts to impose more stringent rulings which enforce greater emissions cuts by corporations and individuals.

This is an emerging global trend. Cases commenced in domestic courts have focused on the interaction between human rights and domestic laws, and often concern international obligations such as those under the Paris Agreement. Governments are the most common respondents to litigation challenging mitigation and adaptation commitments; however, claims have also been brought against corporations and other institutions. For example:

  • against a government: In Notre Affaire à Tous and Others v. France (2021), the Administrative Court of Paris held that the State’s climate inaction and failure to meet its carbon budget goals have caused climate-related ecological damages under international and European climate directives and regulations, the French Environmental Charter, Energy Code and Civil Code. The Court later ordered the State to take immediate and concrete actions by 31 December 2022 to comply with its mitigation commitments under national laws and repair the climate-related ecological damages caused by inaction, including subtracting excess emissions in the subsequent year.5
  • against a corporation: In Mullaley Gas and Pipeline Accord Inc v. Santos NSW (Eastern) Pty Ltd (2021), the Land and Environment Court of New South Wales dismissed a challenge to the approval of a coal seam gas field and associated infrastructure. The Court found that the plaintiffs had not sufficiently established that the Independent Planning Commission, being the entity that approved the project, erred in (i) considering the expected GHG emissions; (ii) excluding Scope 3 or downstream GHG emissions from its assessment; and (iii) failing to consider the climate impacts of gas transmission pipelines.6

It is clear that the number and variety of climate change cases will continue to increase. Such cases may expand their geographical reach, appearing in both developed and developing countries, as well as potential cross-border cases.


Key Takeaways

As of December 2022, there have been 2,180 climate-related cases filed in 65 jurisdictions, including international and regional courts, tribunals, quasi-judicial bodies, or other adjudicatory bodies, such as Special Procedures at the United Nations and arbitral tribunals. Climate litigation, both at international and domestic levels, plays an important role in the global response to climate change, with the advisory opinions representing a crucial tipping point for confirming States’ legal obligations in relation to climate change effects from anthropogenic greenhouse gas emissions.

While the advisory opinions will only consider States’ obligations under international law, there will be several indirect implications on both the public and private sectors including:

  • empowering States to implement more robust climate legislation and Nationally Determined Contributions;
  • the increased risk of claims against States under bilateral and multilateral investment treaties resulting from changes to the international investment framework due to emissions reduction measures;
  • the potential for contentious cases against high emitting or high polluting States or corporations for failures to take steps to curb emissions; and
  • the potential for more domestic cases against governments and corporations based on the findings in the advisory opinions.

We expect many of the positions advanced at the ITLOS proceedings will also influence the positions States advocate for at the upcoming COP28, particularly regarding loss and damage and the obligations on developed States to provide technical and financial assistance to developing countries. Overall, the advisory opinions will play a fundamental role in building momentum for States to adopt clear measures to curb emissions, and to take actions that mitigate and adapt to the ongoing impacts of climate change stemming from anthropogenic greenhouse gas emissions.

Partner Stephen Webb said “The ITLOS and ICJ proceedings, as well as the ongoing European Court of Human Rights climate change proceedings, will significantly alter the course of climate change law and policy on a global scale”.


DLA Piper’s Experience

DLA Piper was proud to appear before ITLOS on a pro bono basis for a Southeast Asian country in the most significant legal proceeding to date in relation to climate change and is advising a number of countries before the ICJ with written submissions due in January 2024. The DLA Piper team at ITLOS comprised Stephen Webb (Partner, Brisbane), Gitanjali Bajaj (Partner, Sydney), the Hon. John Middleton AM KC as Senior Counsel (former judge of the Federal Court of Australia and Senior Advisor at DLA Piper, Melbourne), Eran Sthoeger Esq. as Junior Counsel (New York), Claire Robertson (Solicitor, Brisbane) and Austyn Campbell (Solicitor, Sydney).

DLA Piper has a depth of experience in high profile public international law matters of historical significance. DLA Piper is a leader in understanding and advising on legal liability and the legal risks associated with the impacts of climate change. We advise governments and the private sector on climate change related matters, including being the provider of legal services for COP26. On commercial projects, the firm has been ranked No. 1 for turnover of closed renewable projects and M+A deals closed for a number years now. If you would like further information about the advisory opinions proceedings before the international courts, please contact Stephen Webb or Gitanjali Bajaj.


1 Secretary-General’s opening remarks at the Climate Ambition Summit (20 September 2023), available here
2 London School of Economics, What is climate change legislation? (4 October 2022), available here
3 Westmoreland Mining Holdings, LLC v. Canada, ICSID Case No. UNCT/20/3, Notice of Arbitration and Statement of Claim (12 Aug. 2019), para. 111.
4 Oral submissions of Sierra Leone in the ITLOS Case No. 31 (19 September 2023, ITLOS/PV.23/C31/12), available here.
5 Notre Affaire à Tous and Others v. France (2021), Administrative Court of Paris, Nos. 1904967, 1904972, 1904976/4-1, 21 October (France)
6 Mullaley Gas and Pipeline Accord Inc v. Santos NSW (Eastern) Pty Ltd., New South Wales Land and Environment Court, NSWLEC 147, 16 December 2021 (Australia).