Preface

Ocean Alkalinity Enhancement (OAE) has emerged as a prominent method of marine geoengineering, designed to accelerate the ocean’s natural absorption of carbon dioxide through the dissolution of alkaline substances. Unlike iron fertilization, OAE alters seawater chemistry in ways that may have unpredictable ecological consequences. Proposals for pilot projects in areas beyond national jurisdiction (ABNJ) are on the rise. Yet, the current legal framework for responsibility and liability is underdeveloped.

In the context of the establishment of general duties of States to protect the marine environment, the agreement on the Conservation and Sustainable Use of Marine Biological Diversity of Areas Beyond National Jurisdiction (BBNJ Agreement,2023) augments these obligations by requiring environmental impact assessments (EIAs) and advocating transparency. However, the Agreement contains no explicit liability regime. The key question, then, is whether States can be held responsible under international law for harmful OAE activities conducted by private actors in ABNJ. Recent debates in the law of the sea organs and CILJ’s commentary signal strong caution toward marine geoengineering, with precaution framed as a guiding principle and State positions divided on its permissibility.

Due Diligence After ITLOS and ICJ

UNCLOS due diligence obligations, as reinforced in the ITLOS Climate Advisory Opinion (paras 229–237) and ICJ Advisory Opinion (paras 102–109) which highlight a high standard of due diligence and the integration of precaution into prevention, interpreted in light of recent jurisprudence and reinforced by the BBNJ Agreement, require States to regulate private OAE activities. Accordingly, where such a failure amounts to a breach of the State’s due diligence obligation, it may constitute an internationally wrongful act under Article 2, ARISWA. 

What the Law of the Sea Demands 

A general obligation on States to “protect and preserve the marine environment” has been established under article 192 of UNCLOS.  Further, as per article 194(2), all measures requisite to counteract, lessen and constrain marine environment pollution shall be taken by States, including from activities “under their jurisdiction or control”.

International courts and tribunals have elaborated on the duty of conduct that the relevant provisions entail. In the Pulp Mills case, the ICJ affirmed that a due diligence duty obliges the State to execute an environmental impact assessment when the risk of significant transboundary damage cannot be discounted. This principle is further grounded in international law, under the UNCLOS, States must prevent, reduce, and control pollution of the marine environment under Article 192, 194 and 206.  Broader environmental instruments, such as the Rio Declaration (Principles 2 and 17) and the Espoo Convention, codify the obligation to assess and prevent significant transboundary environmental harm. Together, these judicial and treaty-based sources reflect a coherent due diligence framework across both law of the sea and environmental law. Likewise, in the Advisory Opinion on Activities in the Area, the ITLOS Seabed Disputes Chamber specified that the due diligence obligation comprises “obligations of conduct”, not strict liability; this is directed towards the necessity for States to adopt regulatory frameworks, to supervise compliance, and to impose effective sanctions on private operators who fail to observe the standards. 

Ocean Alkalinity Enhancement (OAE) entails different risks other than the iron-fertilization experiments that have previously raised concerns. Since this technique alters ocean alkalinity, it may disrupt plankton assemblages, disturb  biogeochemical cycles, and compromise fisheries that rely on lower-trophic strata. In light of these foreseeable adverse effects, a State that permits OAE projects from vessels registered under its flag, or from companies incorporated in its territory, must impose rigorous procedures on project approval, on ongoing observation, and periodic public disclosures of the project, including its physical and chemical impacts.

The BBNJ Agreement’s Overlay

The BBNJ Agreement introduces novel obligations relevant to OAE activities in ABNJ. Despite the absence of a liability regime, Part IV of the BBNJ Agreement establishes binding procedural obligations of conduct that operationalize States’ due diligence duties under UNCLOS and international environmental law. Part IV requires States to conduct EIAs (with detailed steps such as screening, scoping, assessment, monitoring, and mandatory publication via the Clearing-House Mechanism) for planned activities in ABNJ that may have higher than a minor or transitory impact on the marine environment. States must publish assessments through a clearing-house mechanism, ensuring global transparency and scrutiny. Although the BBNJ Agreement does not provide for sanctions, yet the breach of its EIA and publication requirements may engage State responsibility under general international law. Which eventually give rise to obligations of cessation, assurances of non-repetition, and exposure to dispute settlement and international scrutiny.

Although the Agreement does not create new liability rules, it reinforces the expectation that States regulate private actors. While the BBNJ Agreement builds on UNCLOS principles, its drafting history indicates the omission of a formal liability regime.  This directs that its obligations rely largely on States’ domestic implementation and good-faith compliance. The failure to require EIAs for OAE projects could constitute a breach of both BBNJ obligations and UNCLOS duties of due diligence. However, this expectation presupposes that States have functional procedural mechanisms. Inefficiencies or delays in conducting EIAs in the high seas context may undermine compliance, though persistent failure to implement adequate procedures could itself amount to a breach of due diligence. Moreover, the BBNJ’s emphasis on scientific cooperation and benefit-sharing underscores the importance of precaution when experimenting with techniques that could have irreversible impacts on ecosystems.

Thus, OAE pilots will likely serve as test cases for the effectiveness of the Agreement in ABNJ governance.

Who Pays if Things Go Wrong?

As per the International Law Commission’s Articles on State Responsibility, States are responsible for actions attributable to them which breach international obligations. Article 8 extends attribution to the actions of private individuals functioning under the direction or authority of a State. This generally requires a threshold of ‘effective control,’ as established in the ICJ Serbia v. Bosnia judgment. Which means that the State must have directed or enforced the specific conduct in question. Even where private entities operate autonomously, Article 11 allows attribution if the State subsequently adopts their conduct. As the State can be held responsible even if it only subsequently endorses or adopts the conduct of otherwise autonomous actors, this allows for a lower threshold of liability. State practice confirms that attribution may arise even where private actors act autonomously. In the Iran Hostages case (United States of America v. Iran), the ICJ attributed the seizure and continued detention of diplomatic personnel to Iran after the State acknowledged and adopted that conduct. Maritime practice reflects the same logic. Where, states may incur responsibility when they authorize private activities or subsequently endorse the acts of private operators.

Beyond attribution, a failure to regulate may itself constitute a breach. The ICJ, in the case of Corfu Channel (United Kingdom of Great Britain and Northern Ireland v. Albania), established that States have an obligation not to intentionally permit their territory to be utilized for conduct that infringes the rights of other States. This preventive duty is reflected in UNCLOS, which requires States to take all necessary measures to protect the marine environment, including conducting environmental impact assessments for activities under their jurisdiction that may cause significant transboundary harm. ITLOS and other tribunals have confirmed that failure to regulate private actors or permit harmful activities under national control can constitute a breach of these obligations, operationalizing the principle established in this case. By analogy, States have a duty not to allow vessels flying their flag or corporations incorporated in their jurisdiction to carry out harmful OAE activities in ABNJ without effective oversight. Accordingly, a State that permits or acquiesces in private OAE experiments, without imposing and enforcing robust due diligence obligations, may expose itself to international responsibility. For instance, the UK requires Marine licenses for ocean experiments. These include environmental assessments, monitoring, and stop-work rules. In the US, NOAA regulates ocean fertilization trials. Baseline studies and independent reviews are mandatory. These examples show that proper oversight ensures that experiments are tested and accountable.

Towards a Regulatory Template

In line with UNCLOS, the BBNJ Agreement, and the Articles on the Responsibility of States for Internationally Wrongful Acts (ARSIWA), a baseline regulatory framework for State authorization of OAE activities in areas beyond national jurisdiction (ABNJ) shall include:

1. Comprehensive environmental impact assessments (EIAs) specifically designed to address the unique chemical and ecological risks posed by OAE;

2. Independent scientific review, with findings made publicly available through the BBNJ clearing-house mechanism;

3. Robust monitoring and reporting obligations, including real-time sharing of environmental data with safeguards to protect commercially sensitive information while enabling regulatory authorities to ensure compliance and address environmental risks; 

4. Insurance or financial security requirements, modelled on liability regimes for oil pollution; and

5. Sunset clauses, mandating periodic review and reassessment of pilot projects.

Embedding such measures would not only give practical effect to States’ due diligence obligations but also bring the precautionary principle to life within the broader framework of marine environmental governance. However , this depends on the diligent implementation of domestic law, considering the precautionary principle remains non-binding soft law and no international liability regime exists to enforce compliance. Yet, it still provides practical legal and policy guidance for OAE governance. By framing regulatory obligations around it, the framework’s conclusions are strengthened, relying on legal and normative considerations rather than solely on the goodwill of States. In addition, binding instruments such as the ILC Convention on the Prevention of Transboundary Harm from Hazardous Activities bolster States’ legal obligations to prevent environmental damage beyond their borders. By framing regulatory obligations around both the precautionary principle and binding international instruments, the framework’s conclusions are strengthened. Eventually relying on legal and normative considerations rather than solely on the goodwill of States.

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Palak Kumari is an undergraduate law student at Guru Gobind Singh Indraprastha University, Delhi. 

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Picture Credit: Foto von Georg Eiermann auf Unsplash