Climate Change and the Peripheries of International Law

By Francesco Sindico - posted on 31 March 2025

On Friday 28 March 2025, I participated in the annual Harvard International Law Journal Forum on the “Peripheries of International Law”. I contributed to the first session on “Environmental Injustice in Small Island States”. On the panel I was joined by Zachary Phillips (Crown Counsel for Antigua and Barbuda), Diem Huong Ho (Associate at Foley Hoag), and Harj Narulla (Barrister at Doughty Street Chambers). The session was chaired by Anne Orford, Harvard Law School and Melbourne Law School.

We were broadly asked to reflect on our personal experience before the recent climate change advisory opinions and to speculate on future legal strategies stemming from such proceedings.

I participated in the International Court of Justice (ICJ) Climate Change State Obligations Advisory Opinion proceedings as Counsel for the International Union for the Conservation of Nature (IUCN). This is what I reflected on in my session, and this blog post provides a snapshot of that contribution.

The ICJ Climate Change Advisory Opinion

Having reviewed the over 100 contributions from States and International organisations before the ICJ, I felt these fell into two major categories.

• On the one hand, you had countries who argued that: a) the ICJ could find answers to question 1 (namely, what are the State obligations to protect the climate system?) in the Paris Agreement and b) that answers to question 2 (what are the legal consequences of the breach of State obligations to protect the climate system?) should also just be framed only as a Paris Agreement matter.
• On the other hand, you had countries who argued that the Paris Agreement has failed in its promise to deliver on the climate emergency and that state obligations to protect the climate system should be found in customary international law and in other international treaties, including human rights treaties. They also argued that the second question about consequences finds its answer in the law of state responsibility, rather than in the Paris Agreement.

Turning to IUCN specifically, it had a unique place in the proceedings, as the only not fully governmental international organisation to be allowed to participate in the proceedings. IUCN presented a more balanced position whereby it argued that:

• state obligations can be found both in the Paris Agreement, in customary international law and in other international treaties. Across the board, it is important to highlight the due diligence nature of such obligations, but also that the 1.5 degrees parameter is of a normative character that allows due diligence to be operationalised in a concrete manner.
• the law of state responsibility does operate in the context of breach of state obligations to protect the climate system, but that the ICJ should refrain from moving into a specific bilateral scenario, which would not belong to the scope of an Advisory Opinion.

Be it as it may, I finished this part of my intervention by stressing that international lawyers live in a world where they are a minority. In my own experience, what the ICJ is, its position within international law, and the potential impact of the Opinion on international climate change cooperation is not well understood within non-legal environments, or even within domestic legal circles. International lawyers, both individually and as groups and networks, need to first acknowledge that they are not at the centre of the global policy discussion and, second, consider how to communicate technical and complex international climate change legal matters to a wider audience. With this in mind, it is important to highlight a key – in my mind – positive outcome of the process before the ICJ: its transparency. Through the written and oral submissions and contributions we now have at our fingertips the position vis-à-vis climate change of all the countries that participated in the proceedings.  

Future climate change legal strategy

In my second contribution I made three key points.

First, just like the adoption of the Paris Agreement in 2015 instigated a wave of climate change litigation, I foresee a second wave stemming from the combined Advisory Opinions from the ICJ, the International Tribunal for the Law of the Sea and the InterAmerican Court of Human Rights. This combination can be seen as a complex puzzle that will provide the foundations for future litigation. However, and this builds on my point above that international law is not always fully understood, one strategy (one objective, a task) for academia is to translate that puzzle so that it can be used by civil society organisations who consider it useful. In other words, we need to make the puzzle (the triple Advisory Opinion outcome) accessible. An important point that was raised in the question and answer after our interventions was one around funding litigation and the role of local civil society organisations in triggering such funding. The extent to which such funding can also (or should also) be used to talk about and try to decipher the puzzle is open for debate.

The second point I made in this part of the session focused on Small Island Developing States (SIDS). I argued that

• litigation is important, but is part of a wider landscape of multilateral efforts that need to be considered;
• in some cases such efforts do not focus specifically on climate change, but are incredibly important to deal with climate change mitigation and adaptation; and
• the real question is, how does the puzzle mentioned above relate to these multilateral processes, which leads us again to the challenge of translating technical international legal processes and outcomes to non-legal stakeholders involved in such processes.

I clarified that the processes I am referring to are:

• The implementation of the Antigua and Barbuda Agenda for SIDS (ABAS) and the future process leading to a revision of the Sustainable Development Goals
• The UN Conference for Finance and Development, which will conclude in Seville in June 2025. In this respect the interesting question is the link between debt relief and possible remedies in future inter-state climate change disputes
• The United Nations Ocean Conference process. Here, the question of the right to self determination vis-à-vis sea level rise and loss of statehood highlights the existential nature of climate change for SIDS.
• The United Nations Water Conference in 2026 with key moments in Senegal in late 2025 and the conference in the United Arab Emirates in 2026. Here, the link between the right to water and negative impact on freshwater resources on SIDS becomes crucial.

Having reflected on climate change and multilateralism, I concluded my intervention with a third and final point reminding the audience that the world has changed over the past three months. In almost all the multilateral processes mentioned above the USA would have played a key, or at least some, role. The question to which I do not have an immediate answer is whether this should be considered as the nail in the coffin of multilateralism, or possibly as an opportunity to leverage a new, better, form of multilateralism.