A personal account by Dr. Jan Yves Remy (External Counsel for Saint Lucia in the ICJ Advisory Opinion Proceedings)

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1)  Treaty Obligations — Hard Law, Not Aspirations

On the treaties, the Court grouped duties as we did: it found that relevant obligations of mitigation, adaptation, and cooperation (finance, technology, capacity) applied.  It read them as legal obligations borne by stringent due diligence, contextualized by COP decisions and practice.  Crucially, the Court rejected the view that open-textured language in the UNFCCC and Paris Agreements (“take full account”, “give full consideration”) reduces the provisions to mere aspirations.

This was vindication of our Annex II argument that provisions concerning SIDS and LDCs (UNFCCC Arts 4.4–4.8; Paris Art 2.2 and Preamble) have legal content. The Court agreed in principle. Where it was more cautious — as we feared — was on the specific obligations relating to finance and capacity building:  while affirming support in finance and technology are an obligation but left the quantum and channels to politics and in concreto cases.

2) Customary Law and UNCLOS — Prevention, Due Diligence, and Cooperation

A key pillar of the Opinion is customary law and the principles it embodies—such as the duty of prevention, which requires a stringent due diligence obligation to avoid significant transboundary harm. This duty is operationalized through domestic regulation, environmental impact assessments, notification, consultation, and cooperation. Here again, the Court echoed our framing.

Importantly, the Court linked these obligations to the obligation to the marine environment via UNCLOS. It cited Article 206 (EIAs) and Article 194 (pollution prevention), holding that GHG emissions fall within their scope. It instructed States to “cross-read” UNCLOS and Paris obligations — systemic integration in action.

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ITLOS’s May 2024 Advisory Opinion was referenced and validated. The ICJ drew on ITLOS’ articulation of due diligence, precaution, and special consideration for SIDS in interpreting UNCLOS.  Interestingly, it was unencumbered in its reliance on that case law – advancing the coherent approach to international law especially on the topic of climate change.  It was also confirmation that our regional effort — joining COSIS and building the law of the sea case — mattered.

3) Attribution, Conduct, and Causation

Here lies one of the Opinion’s most consequential moves. The Court clarified that attribution follows established rules of international law, and that “relevant conduct” is not limited to direct emissions. It includes licensing, permitting, and subsidising fossil fuel activities.  In other words, States cannot insulate themselves by pointing to private actors; they are responsible where they fail to regulate or supervise them – a far-reaching finding in terms of which types of activities, beyond just state actors, are implicated.

On causation, the Court was nuanced. It did not require pinpoint attribution to one State. Instead, it recognized that in a global harm situation like climate change, causation can be established through contribution to risk and harm, taken together. This reflects exactly what we and other SIDS argued: that collective conduct can ground legal responsibility, even if individual shares vary. It leaves the door open for future in concreto claims to establish liability on the basis of contribution, not dominance.

4) State Responsibility and Legal Consequences

Another important finding of the Court – as we had argued – is that the rules on State Responsibility – ARSIWA – apply. The Court confirmed that the climate treaties are not self-contained, and that breaches of treaty and custom alike trigger the consequences of State responsibility: continued performance, cessation, guarantees of non-repetition, and reparation.

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Here the Court invoked obligations erga omnes — duties owed to the international community as a whole. Protecting the climate system, the Court said, is an obligation erga omnes, meaning that all States have a legal interest in compliance, whether or not directly injured.  This was a breakthrough: it means SIDS need not stand alone; any State can invoke these obligations in future proceedings.

On reparation, the Court stopped short of fixing liability or specifying finance quantum. It left those for politics and specific cases. But it confirmed that reparation — restitution, compensation, satisfaction — applies, and that existing finance mechanisms do not preclude responsibility. They are cooperative pathways, not liability shields.

5) What It Did Not Say — SIDS and Obligations owed

For SIDS, the Opinion is both vindication and frustration. It hardened obligations we care about — Paris as binding, CBDR-RC as interpretive thread, UNCLOS duties applied to GHGs, prevention and cooperation as custom, erga omnes standing, and attribution rules that encompass subsidies and licensing. But it did not name SIDS specifically, nor did it give the granular finance consequences we had sought.

Sea level rise, existential threats, and vulnerabilities were present through the Opinion’s reliance on IPCC science. Our arguments lived between the lines. It would have been satisfying to see “Helen” herself mentioned, but recognition came indirectly in Judge Charlesworth’s Separate Opinion. She chose to dwell on the imagery offered by SIDS and climate-vulnerable groups, citing the testimony of a Pacific I-Kiribati villager describing how his community had become “scattered, broken” after relocation, the story of women walking further and further inland to fetch freshwater as saltwater poisoned their wells, children suffering malnutrition, women losing traditional craft materials, and disabled people in Tuvalu unable to reach safety during floods.

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For her, these were not rhetorical flourishes but evidence of how law must be interpreted through lived experience. That acknowledgment matters. Even if the Court as a whole stopped short of naming SIDS, a judge of its bench validated the imagery and voices that we and our peers had brought. It was a recognition — if only indirect — that our stories belong to the law.

6) A Court Within Its Limits

The Court also reflected on its own place. It emphasized that its role was limited—that it would not legislate finance or overstep into political bargains. It explained that:

The Court… can do more than address the questions put to it through and within the limits of its judicial function; this is the court’s assigned role in the international legal order.

This was the Court’s way of answering our plea without overreaching. It set the legal scaffolding and left the building for us to complete. Its approach in general reminds me very much of some of the early case law of the ECJ and the Caribbean Court of Justice when they were just establishing their authority—forceful in articulating obligations, but more restrained in specifying legal consequences. As creatures of international (and political) processes, they understand all too well that, in the final analysis, it is States that remain the primary objects of the law.

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7) My Closing Reflections

So did we really win?

Judged by the main thrust of the Court’s Opinion, I would certainly say that we won this battle. The Court gave us more than we expected, even if less than we hoped. For SIDS, it crystallized our core arguments: obligations are binding; prevention and cooperation are customary duties; UNCLOS applies; ARSIWA remains available; obligations are erga omnes; and attribution rules capture conduct we had highlighted, such as fossil fuel subsidies. It did not name us directly, but it wrote our survival into the law’s logic. Like Helen herself, our arguments were present even when unspoken. And like Helen, we endure.

But it is harder to say whether we have won the war. As lawyers, we will put these arguments to maximum effect in the various theatres of ongoing negotiations—whether at the WTO, where we seek to strengthen climate-related arguments, or in efforts to reform fossil fuel subsidies; in the IMO, where we press for greater representation of SIDS; at COP30, where we will demand more robust support for finance-related obligations; or in the broader push for reform of international financial institutions and debt rules that currently weigh heavily on countries being asked to shoulder the costs of adaptation. Even domestically, the Opinion will inform how we prepare the next cycle of NDCs and how governments allocate climate and ODA budgets.

The real test lies beyond law and negotiating theatres – it will lie in whether it can change hearts and minds, and ultimately behaviours. Will this decision prick the conscience of decision makers—or of the citizens they serve? Will it make one more politician pause when a scientist speaks? Will it influence the decision to direct more resources to countries and causes that may not seem immediately relevant, but could save a home, a life, or even the future of someone far away—or indeed, the lives of their own children, who five or ten years from now may ask why their leaders and people did not do more?

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As for me, the Opinion marked the culmination of a journey. It reminded me that, even as I remain a tiny cog in a big wheel, I can use my voice, my determination, and my skills to advance the needs of my country, my region, and humanity. It offered the rare opportunity to make Saint Lucia visible in the world’s highest court, and to leave a record that our island, and SIDS everywhere, were not silent in the face of the rising sea.