Climate Governance under the London Convention and Protocol: Precaution and Prevention – Climate Law Blog

Introduction

Parties to the 1972 Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter (London Convention) and the 1996 Protocol to the Convention (London Protocol)—two international treaties that aim to protect to the marine environment from human activities—are set to meet in the last week of October 2025. High on the agenda is the governance of marine geoengineering activities, including marine carbon dioxide removal (mCDR) approaches. Last month, the Sabin Center published a white paper on international legal principles and guidelines that should guide these discussions. In this blog post—the first in a series of three—we discuss some of the key findings from that paper. In particular, we focus on two bedrock guidelines in international environmental law—the precautionary approach and the prevention principle—that should guide the parties approach to governing mCDR under the London Convention and Protocol. Subsequent blogs will discuss other relevant guidelines.

For the past two decades, parties to the London Convention and Protocol have negotiated rules, decisions, and amendments related to climate change. These efforts have principally focused on two sets of technologies – sub-seabed carbon dioxide storage and marine geoengineering. Initial discussions regarding marine geoengineering focused specifically on ocean fertilization but, more recently, the parties have considered an expanded array of mCDR approaches, including ocean alkalinity enhancement and ocean sinking of biomass. (For more info on the 2023 meeting of the parties, including the 2023 Statement on Marine Geoengineering, see our blogs here and here. For more info on the 2024 meeting, including governance options parties considered but have not yet adopted, see our blogs here and here.)

Throughout their discussions, parties to the London Convention and Protocol have rightly invoked legal principles and guidelines, like the precautionary approach, to inform their assessment of how to apply the treaties to climate-related activities. Recent developments in international law, including important pronouncements by the International Court of Justice (ICJ), the Inter-American Court of Human Rights (IACtHR), and the International Tribunal for the Law of the Sea (ITLOS) on the application of international law in the context of climate change, clarify the meaning and scope of these legal guidelines. Among the guidelines that were addressed by the courts are the precautionary approach and the prevention principle. These same guidelines are also highly relevant for mCDR governance under the London Convention and Protocol, since they are specifically referenced in the treaties, and parties frequently invoke them in their discussions and decisions.

As discussed further below and elaborated on in our recent paper, the ICJ, IACtHR, and ITLOS opinions shed new light on how the precautionary approach and prevention principle should be applied in the context of climate governance, which has clear implications for mCDR governance. The opinions indicate that, in developing a governance framework for mCDR, parties to the London Convention and Protocol should take a holistic approach that considers not just the risks associated with mCDR activities but also their potential benefits. Specifically, parties should apply the precautionary principle in a way that does not unduly delay actions to protect the environment, including climate mitigation actions. Moreover, parties should apply the prevention principle at least on equal footing with the precautionary principle and, to this end, consider the potential for regulation to aid in preventing transboundary harm from climate change.

Relevance of the Advisory Opinions to the London Convention and Protocol

Understanding of country obligations to respond to climate change has significantly expanded in the last two years. This is because three different international courts / tribunals—the ICJ, IACtHR, and ITLOS—have issued advisory opinions on climate change. While these opinions are non-binding, they represent clear, authoritative statements on the application of international law and human rights law to climate change governance. The opinions have implications for country actions domestically and internationally, including the steps countries take in negotiating international treaties that are relevant to climate change, like the London Convention and Protocol.

There is a debate in international climate law about whether parties to a given treaty must only take that treaty’s text into account when negotiating rules under the treaty, or whether they must consider a broader range of international legal authorities. For example, some country submissions to both the ICJ and ITLOS argued that their obligations to mitigate climate change are entirely discharged through their participation in the UN Framework Convention on Climate Change (UNFCCC) and the Paris Agreement. In other words, they argued that countries do not have international legal obligations to mitigate climate change beyond what is included in the UNFCCC and the Paris Agreement. However, both the ICJ and ITLOS rejected this view. They found that parties must consider relevant international legal guidelines and other relevant treaties when interpreting their climate obligations under a given treaty. As the ICJ wrote, “[t]reaties, in particular multilateral environmental treaties, need to be interpreted by taking into account any relevant rules of international law that are applicable in the relations between the parties.”

All of the parties to the London Convention and Protocol are also parties to the UNFCCC and other key climate agreements. The advisory opinions indicate that countries should interpret their obligations to address climate change in a consistent way across these treaties.

In the past, parties to the London Convention and Protocol have identified climate change mitigation as worthy objective of regulation under the London Convention and Protocol. In the context of facilitating the export of carbon dioxide streams for carbon capture and storage (CCS) projects, for example, the parties discussed enabling CCS to help “meet[] the climate targets set in the Paris Agreement.” More recently, in the context of mCDR regulation, the parties recognized the need “to confront the challenges posed by global climate change.” Implicit in the parties’ statements is a recognition that regulating in a manner that advances climate change is consistent with the overall objectives of the London Convention and Protocol – to protect and preserve the marine environment. As both ITLOS and the ICJ have recognized, climate change is already having “deleterious effects … on the marine environment,” and states must take “far-reaching” measures to avoid and mitigate those effects.

Precaution

The precautionary principle, also known as the precautionary approach, stands for the proposition that, in the face of serious damage, countries will not use lack of full scientific certainty to postpone environmentally protective actions. The principle was first defined in an international instrument in the Rio Declaration in 1992 as follows:

“In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.”

In other words, the precautionary approach cautions against using scientific uncertainty as a reason to delay action to protect the environment. The precautionary approach is specifically referenced in Article 3 of the London Protocol. While it isn’t mentioned in the London Convention, in 1991, the parties adopted a decision stating that implementation of the Convention “shall be guided by a precautionary approach to environmental protection.”

The precautionary approach has been central to governance decisions on ocean fertilization and other forms of mCDR under the London Convention and Protocol. The approach is cited in several decisions, including a 2008 resolution on the governance of ocean fertilization, a 2010 resolution on an assessment framework for scientific research involving ocean fertilization, and the 2023 statement on marine geoengineering. In these decisions and other discussions, the parties have focused on the environmental risks of mCDR and concluded that, given scientific uncertainty regarding the risks of mCDR, a precautionary approach requires restricting mCDR.

Recently, the parties to the London Convention and Protocol have recognized the need to also consider the potential benefits that might flow from mCDR activities, including their climate change mitigation potential. This more holistic assessment of mCDR is consistent with the original and continued legal understanding of the precautionary approach. As ITLOS found, “[f]or marine pollution arising from anthropogenic GHG emissions, the precautionary approach is all the more necessary given the serious and irreversible damage that may be caused to the marine environment by such pollution, as is assessed by the best available science.”

Thus, a precautionary approach requires not only consideration of the environmental risks associated with mCDR activities but also the risks of failing to address climate change. Such an approach would better align the parties work under the London Convention and Protocol with their commitments under other international agreements, including the UNFCCC and the Paris Agreement.

Prevention

The principle that countries must prevent activities within their control from causing transboundary harm is a bedrock principle of international environmental law. A clear articulation of the principle can be found in Principle 21 of the Stockholm Declaration, under which countries have “the responsibility to ensure that activities within their jurisdiction or control do not cause damage to the environment of other States or of areas beyond the limits of national jurisdiction.” Courts, including the ICJ, have found that the obligation of States to prevent transboundary harm forms part of customary international law, meaning it is binding on all countries. Both the London Convention (in the preamble) and London Protocol (in Article 3) include explicit directions to prevent transboundary harm.

There is a growing consensus that parties have a duty to prevent transboundary harm from climate change in order to uphold their obligations under customary international law. ITLOS, in its advisory opinion, found that countries must “take all necessary measures to prevent, reduce and control marine pollution from anthropogenic GHG emissions.” Though ITLOS was discussing party obligations under the UN Convention on the Law of the Sea (UNCLOS), not the London Convention and Protocol, party obligations under both instruments are closely intertwined, as explained in the paper.

ITLOS further found that parties to UNCLOS have an obligation to protect and preserve the marine environment “to combat any form of degradation of the marine environment, including climate change impacts, such as ocean warming and sea level rise, and ocean acidification.” This obligation “may include restoring marine habitats and ecosystems” where the marine environment has been degraded. If mCDR projects are able to restore marine ecosystems, they could be seen as a tool to protect and preserve the marine environment in line with marine treaty obligations.

As discussed above, parties the London Convention and Protocol have frequently cited to the precautionary approach as guiding their governance of mCDR, but have not consistently referenced prevention in their decisions. Going forward, parties should apply the principle of prevention on at least equal footing with the precautionary approach, given the express references to the principle of prevention in the London Convention and Protocol, and its status as customary international law.

In the context of mCDR governance, the principle of prevention requires parties to develop a framework that seeks to prevent harms from both mCDR projects and from climate change. Recent efforts to consider the climate benefits of mCDR, alongside environmental risks, set the stage to do so with greater clarity.

Conclusion

The precautionary approach and the prevention principle have a direct bearing on governance of mCDR activities under the London Convention and Protocol. To apply the guidelines properly, parties should invoke the precautionary approach in a way that does not unduly delay actions, including climate mitigation actions, to protect the environment. Further, parties should apply the prevention principle at least on equal footing with the precautionary principle. This should include analyses of the potential of regulation to aid in preventing transboundary harm from climate change.

As discussed above, this blog summarizes arguments that are more fully fleshed out in our white paper on “International Legal Guidelines for Marine Carbon Dioxide Removal Governance under the London Convention and London Protocol.” This is the first in a three-part blog series that discusses the findings of that paper and places them in context. The two upcoming blogs will analyze 1) the relevance of due diligence and environmental impact assessments to the governance of mCDR under the London Convention and Protocol and 2) the governance of sub-seabed sequestration of carbon dioxide under the treaties.