Published June 27, 2024
By Upasana Khatri, Senior Attorney at the Center for International Environmental Law, and Joie Chowdhury, Senior Attorney, Climate Litigation and Accountability at the Center for International Environmental Law.
On May 21, 2024, the court for the world’s oceans became the first international court to declare that States have a legal duty to protect the oceans from the drivers and impacts of climate change. In its landmark advisory opinion (AO), the International Tribunal for the Law of the Sea (ITLOS) confirms that greenhouse gas (GHG) emissions are a form of marine pollution that States must prevent, reduce, and control. The AO clarifies the obligations of State Parties to the United Nations Convention on the Law of the Sea (UNCLOS) in the context of the climate emergency, and makes clear that State obligations to act on climate extend beyond those under the United Nations Framework Convention on Climate Change (UNFCCC) and its Paris Agreement. This lays the foundations for future judicial pronouncements on climate duties and raises the bar for future policy decisions on climate action.
The Path to the ITLOS Climate Advisory Opinion
This historic moment was the culmination of a process initiated in 2022 by the Commission of Small Island States on Climate Change and International Law (COSIS), a coalition of Small Island Developing States (SIDS) that, despite contributing the least to anthropogenic climate change, are among those most vulnerable to its impacts. In its request for an advisory opinion, COSIS asked ITLOS to clarify:
(1) the obligations of State Parties to UNCLOS to prevent, reduce, and control anthropogenic greenhouse gas emissions as the primary driver of climate change, ocean acidification, and related harms to the marine environment; and
(2) the obligations of State Parties to affirmatively protect and preserve the marine environment from such harms.
The AO process drew the unprecedented participation of more than fifty States, international organizations, and civil society organizations (including CIEL), who weighed in through written submissions and/or oral interventions.
Significance of the First Climate Advisory Opinion
This opinion sets the floor — not the ceiling — for future decisions on climate and international legal duties. ITLOS is the first of three international courts to deliver its opinion on climate, so its findings are expected to provide critical guidance to the Inter-American Court of Human Rights (Inter-American Court) and the International Court of Justice (ICJ), which will issue their respective climate advisory opinions within the next year. As the preeminent authority on the law of the sea and the first international court to weigh in on State obligations in relation to climate change and oceans, ITLOS can specifically inform how the ICJ and the Inter-American Court understand States’ international duties to protect the oceans in the context of the climate crisis, and more broadly, how they define States’ obligations regarding climate change.
Moreover, the three AO processes together represent a once-in-a-generation opportunity for international judicial bodies to clarify State responsibilities to confront climate change under international law, which could have ripple effects for decades to come. As authoritative interpretations of binding international law, AOs carry great legal weight. The ITLOS AO, along with the forthcoming climate advisory opinions from the Inter-American Court and the ICJ, will undoubtedly influence other courts’ interpretation of State duties, and thus the rulings in pending and future cases, as well as the development of laws and policies around the world. Moreover, they may help cut through the political inertia that has long stalled progress in international climate negotiations and national climate policymaking. Specifically, the ITLOS AO may bring oceans to the forefront in climate negotiations, discourse, and action.
Pivotal Legal Elements of the ITLOS AO
The ITLOS Advisory Opinion offers many strong interpretations of what the law of the sea requires of States in the face of the climate crisis, in relation to other relevant international legal norms and principles. Several key takeaways are summarized below:
Anthropogenic GHG emissions constitute “pollution of the marine environment.” This finding, a necessary precondition to trigger States’ duties under UNCLOS to protect and preserve the marine environment in the context of climate change, is consistent with the position taken by almost all of the State delegations to the advisory proceedings, with the notable exceptions of India and China. ITLOS affirmed that anthropogenic GHG emissions are a form of marine pollution since, per Article 1 of UNCLOS, they result in “substances” (i.e., carbon dioxide) and “heat” entering the marine environment, which then leads to “deleterious effects” such as ocean warming, sea level rise, and ocean acidification. States have a duty to take all measures necessary to “prevent, reduce, and control” such pollution, whether it stems from land-based sources, vessels, or aircraft.
To satisfy their legal duty, States must undertake measures that meet a stringent, objective standard of care. The ITLOS AO clarifies that the obligation of States to take all necessary measures to prevent, reduce, and control marine pollution from anthropogenic GHG emissions, as well as protect and preserve the marine environment from climate change impacts, is grounded in the duty of due diligence. And the Tribunal emphasizes that what constitutes “necessary measures” should be determined objectively, taking into account the best available science and the 1.5°C limit. States do not have unfettered discretion to adopt just any measures to protect oceans from the drivers and impacts of climate change. Reaffirming the importance of corporate accountability, the Tribunal emphasizes that the “obligation of due diligence is particularly relevant in a situation in which the activities in question are mostly carried out by private persons or entities.”
The more severe a risk, the more stringent the due diligence required. Given that GHG emissions present a known risk of irreversible harm, States must meet a heightened standard of care. The Tribunal reaffirms that “the standard of due diligence has to be more severe for riskier activities.” Because anthropogenic GHG emissions “pose a high risk in terms of foreseeability and severity of harm,” the standard of due diligence that States must exercise in relation to regulating such emissions “needs to be stringent.” To meet the specific obligation to “take all necessary measures” to prevent, reduce, and control marine pollution by anthropogenic GHG emissions, States must do the “utmost” to obtain the intended result of these measures: the reduction of GHG emissions into the atmosphere. ITLOS has further found that the standard of due diligence can be even more stringent in relation to the duty to prevent transboundary harm. The AO notes that, in requiring States to prevent not only harm to other States’ territories but also the “‘spread’ of pollution,” UNCLOS establishes that States’ mitigation duties extend not only to “damage that actually occurred but also to damage that is likely to occur.”
States must be guided by the best available science. Throughout its AO, ITLOS recognizes the centrality of science to the questions before it, and notes that “[w]ith regard to climate change and ocean acidification, the best available science is found in the works of the Intergovernmental Panel on Climate Change which reflect the scientific consensus.” The Tribunal calls for State action to take into account “the global temperature goal of limiting the temperature increase to 1.5°C above pre-industrial levels and the timeline [under the Paris Agreement] for emission pathways to achieve that goal.”
The Paris Agreement does not exclusively or exhaustively define State obligations in relation to climate change. The ITLOS AO is clear: States do not meet their international legal obligations related to climate change simply by fulfilling the obligations contained in the Paris Agreement or through mere participation in “global [climate] efforts.” Firmly rejecting some States’ arguments to the contrary, the Tribunal states that while Paris complements UNCLOS in relation to the regulation of marine pollution from anthropogenic GHG emissions, the former “is not lex specialis” — meaning it does not displace or supersede UNCLOS. Rather, UNCLOS imposes separate, specific obligations. Thus, even if State Parties are in compliance with the Paris Agreement, if they fail to fulfill their obligation to take all necessary measures to prevent, reduce, and control marine pollution from anthropogenic GHG emissions, they could face “international responsibility,” or in other words, liability. Such responsibility may require the State to cease its wrongful conduct — such as acts and omissions that result in GHG emissions at a scale causing significant harm to the climate system — and to provide full reparations for resultant injuries. This finding suggests that it could be possible for claims to be brought under UNCLOS for loss and damage or climate harm stemming from inadequate regulation of marine pollution by GHG emissions.
While equity is central, all States are duty-bound to take action to reduce GHG emissions. In line with the international law principle of Common but Differentiated Responsibilities and Respective Capabilities (CBDR-RC), the opinion recognizes that States with “greater means and capabilities must do more to reduce [anthropogenic GHG] emissions than States with less means and capabilities.” However, ITLOS makes clear that all States are obligated to do whatever they can to prevent, reduce, and control GHG emissions — including mitigation measures and individual action — even if developed countries should “continue taking the lead.” Indeed, the Tribunal advises that States may not use UNCLOS’s reference to “available means and capabilities” as an excuse to “unduly postpone, or even be exempt from, the implementation of the obligation to take all necessary measures.” In line with an equitable approach to climate action, the opinion also holds that States Parties have the specific obligation to assist developing States, particularly vulnerable developing States, in their efforts to address marine pollution from anthropogenic GHG emissions.
States must further take a precautionary approach in addressing GHG pollution; conduct environmental impact assessments while considering cumulative effects; and assess the consequences of risky, speculative technological actions. In addition to the foundational elements already addressed, there are other vital aspects of the ITLOS AO critical for climate accountability. These include the Tribunal’s emphasis on the importance of taking a precautionary approach when implementing measures to address GHG pollution, and States applying an ecosystem approach (which can entail balancing ocean, coastal, and freshwater resource use with conservation, ensuring ecosystem health and connectivity) to effectively protect and preserve the oceans against climate change impacts. Additionally, the Tribunal provides substantive guidance on the obligation to conduct environmental impact assessments (EIAs), noting the importance of evaluating the GHG impact of a proposed activity not in isolation but cumulatively, in light of its interaction with other GHG-generating activities. Further, the ITLOS AO sounds a note of caution in relation to risky, speculative, and unproven technological responses to the climate crisis. Specifically, the opinion underlines that marine geoengineering — large-scale intervention in the Earth’s climate system, such as ocean-based carbon dioxide removal (CDR) — would be contrary to UNCLOS if it has the consequence of introducing pollutants to the marine environment or transforming one type of pollution into another.
Opportunities for Further Progress
While the opinion offers strong and progressive interpretations of State obligations in relation to climate change, there are key areas where the forthcoming climate advisory proceedings and pending and future climate litigation at national and regional levels can and should go further. For example, future opinions can expand on how international human rights law defines the precise scope and content of States’ obligations, and address questions that ITLOS did not squarely reach, such as the legal consequences for States that breach their climate duties. Additionally, the ICJ and Inter-American Court will hopefully take the much-needed step to explicitly name that, in line with what the best available science makes clear, ambitious and equitable reduction of GHG emissions unequivocally requires the phaseout of fossil fuels.
Advancing Climate Justice
The ITLOS AO represents an important step forward in effectively safeguarding two global commons — the oceans and the atmosphere — whose fates are intertwined and imperiled by the climate crisis. States who face the worst impacts of the climate crisis have demonstrated admirable leadership throughout the advisory opinion proceedings, which underscores the key role of these States, particularly SIDS, in the development and application of international law to advance climate justice. In the words of Gaston Browne, Prime Minister of Antigua and Barbuda: “We are, after all, peoples of the ocean, whether in the Caribbean or the Pacific, in the Atlantic or Indian Oceans, surrounded by the vast expanses of water that have sustained us from time immemorial.”
Protecting the oceans and atmosphere is a matter of life and death — not just for entire marine ecosystems and the coastal and island communities they support, but for all of humanity and the planet as a whole.