âOnce the Lawyers Move In, You Know the Problem Is Seriousâ
Last July, the International Court of Justice delivered its unanimous advisory opinion on climate change. The courtâs answer was unambiguous. Climate obligations are legal, substantive, and enforceable: states have stringent duties to protect the climate system, breaching them constitutes an internationally wrongful act, and the 1.5°C target has been identified as the legally anchored agreed primary temperature goal under the Paris Agreement. Eighteen months after we first spoke with Marie-Claire Cordonier Segger, Tejas Rao and Markus Gehring, three climate law scholars at the University of Cambridge, about the then-upcoming opinion, we asked them to take stock of what has actually changed: in courts, in multilateral diplomacy, and in the growing coalition of states willing to move ahead without waiting for the holdouts.
1. Almost exactly one and a half years ago, we spoke about the then-upcoming advisory opinion of the International Court of Justice on climate change. Since then, the ICJ has issued its unanimous opinion. Is it already possible to say something about its impact â on international climate law, on domestic litigation, or on the broader politics of climate governance?
When we spoke at the end of 2024, we anticipated that the Court would have an opportunity to make a meaningful contribution to clarifying international law. The unanimous opinion of all fifteen judges on 23 July 2025 went considerably further than that. It is, in our view, the most consequential pronouncement on sustainable development law since the GabÄĂkovoâNagymaros judgment, and a vindication of the vision Judge Weeramantry provided in his opinion.
Three dimensions of impact are already discernible. First, in the discursive and epistemic field, the Advisory Opinion (AO) has reshaped what is sayable in legitimate legal argument. Major emittersâ lex specialis defence, i.e., that the Paris Agreement displaces customary obligations, has been authoritatively rejected, and arguments grounded in due diligence, the duty to cooperate, intergenerational equity, and the human right to a healthy environment have moved from advocacy briefs into the central legal mainstream, though the Court left open the question of how the Paris Agreementâs NDC architecture shapes the content and stringency of the customary due diligence obligation in practice. Several NGOs have already produced a structured digest of âlitigation notesâ enabling counsel in pending domestic cases to plug specific paragraphs of the AO into their pleadings. Second, in operative legal terms, the Courtâs endorsement of the 1.5°C threshold as the agreed primary temperature goal under the Paris Agreement (para. 224) settles a debate that Urgenda, Neubauer, KlimaSeniorinnen, and many other domestic cases had been answering in fragmented ways. Third, the global politics advocating against the ICJ Opinion has itself become revealing. At COP30 in BelĂ©m, several countries described any reference to the AO in the Warsaw International Mechanism text as a âdeep, deep, deep red lineâ; the United States has, since the change of administration, characterised the AO as advancing âmisguided claims of international legal obligationsâ. Such resistance is, paradoxically, the clearest indicator of the opinionâs weight. Across all seven New Delhi principles of sustainable development law, from equity and common but differentiated responsibilities to good governance and integration, this AO confirms what we have long argued: these are not aspirational maxims but operative legal norms. As Marie-Claire and Damilola Olawuyi argue, this is also crucial for our understanding of sustainable development law, since out of 193 UN members, approximately 58 are highly climate vulnerable but another 134 are also from developing countries, and will need ways to ensure their development strategies can transition away from fossil fuel dependency without being locked into outdated economic models.
More concretely, litigants in domestic courts are already citing the ICJ AO, for example:
The ICJâs 2025 Advisory Opinion on the Obligations of States in respect of Climate Change has begun to permeate domestic and regional adjudication with remarkable speed. In Canada, the Federal Court in Dini Zeâ Lhoâimggin v. His Majesty the King in Right of Canada (2025 FC 1586) acknowledged that although the Advisory Opinion is not binding in Canadian courts, it âcan influence how courts interpret domestic laws, particularly in relation to constitutional rights and international obligations,â and treated it as reinforcing the viability of a novel common law tort claim grounded in customary international law duties to protect the climate system. In the Netherlands, the District Court of The Hague in Stichting Greenpeace Nederland et al. v. The Netherlands (Bonaire) (28 January 2026) expressly relied on the Advisory Opinion as authoritative interpretative guidance, using it to clarify that statesâ climate obligations entail due-diligence duties of conduct and, in certain respects, obligations of result, thereby strengthening the benchmark against which Dutch mitigation and adaptation efforts were assessed. In Mexico, the Supreme Court of Justice of the Nation in Amparo en RevisiĂłn 450/2025 (24 February 2026) cited the ICJ Advisory Opinion alongside the Inter-American Courtâs OC-32/25 as persuasive authorities underpinning the precautionary principle and the reversal of the burden of proof in environmental cases.
At the regional level, the European Court of Human Rights in Greenpeace Nordic and Others v. Norway (28 October 2025) situated its articulation of procedural obligations under Article 8 ECHR within a converging body of international authority that included the ICJ Advisory Opinion, the ITLOS opinion, the IACtHRâs OC-32/25, the EFTA Courtâs advisory opinion, and the UK Supreme Courtâs Finch judgment. The Strasbourg Court cited the ICJâs finding that states must undertake climate-related assessments for proposed industrial activities in a transboundary context, and characterised its own conclusion â that environmental impact assessments for petroleum projects must assess downstream and exported emissions based on the best available science â as âparalleledâ by these international rulings. Taken together, these decisions demonstrate that courts are treating the Advisory Opinion not as a remote statement of public international law but as a live interpretive tool capable of shaping the content of domestic constitutional rights, the standard of due diligence expected of states, and the procedural rigour required before fossil fuel projects may be authorised.
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2. The driving force behind the request for the advisory opinion was the Pacific island state of Vanuatu. Now Vanuatu has tabled a new resolution for the UN General Assembly. What is this resolution about â and what does it actually add to the advisory opinion?
The Vanuatu-led resolution is best understood as the institutional articulation of the AO within the political organ that requested it in the first place. The Court declares what international law requires; the General Assembly says, collectively, that it accepts that declaration and undertakes follow-through. The resolution does this with considerable care. This should not even become part of a political process, as the GA requested the opinion and, of course, has received an authoritative legal opinion. Welcoming the advice was always seen as a normal step of acceptance and implementation.
Its operative core contains important elements. It welcomes the AO as âan authoritative contribution to the clarification of existing international lawâ, phrasing deliberately chosen to head off the predictable objection that the resolution somehow creates new obligations. It then enumerates the Courtâs most contested findings and translates each into a call upon states: the stringent due diligence standard under the customary duty to prevent significant harm, the duty to cooperate in good faith, the obligation to respect and ensure human rights in climate action, and the full Articles on State Responsibility package, cessation, assurances and guarantees of non-repetition, and full reparation in the form of restitution, compensation and satisfaction, subject to the usual conditions of causation and attribution. It also stabilises two findings on which several major emitters had hoped for ambiguity: the continuity of statehood notwithstanding sea-level rise, and the preservation of duly established maritime baselines under UNCLOS, both critical to the legal personality and entitlements of low-lying states.
What does the resolution add? In strict doctrinal terms, very little is new, and that is precisely the point. General Assembly resolutions do not legislate; they consolidate and signal. But politically, they do three things the AO alone cannot. They build a roll-call of supportive states. They place the Secretary-General under a reporting mandate for the 82nd session on advancing compliance. And they recommend follow-up on the provisional agenda for the 83rd session. That last point is, in our view, the most important. It transforms a one-off advisory pronouncement into a recurring institutional item in the General Assembly. Importantly, this timeline is not accidental. The 83rd session will coincide with the early stages of the second Global Stocktake process, due to conclude at COP33 in 2028. By anchoring the AOâs implementation as a recurring GA agenda item on the same political calendar as the GST ratchet mechanism, Vanuatu and the core group are creating a structural opportunity for the legal obligations confirmed by the Court to inform the ambition assessment that the GST is designed to generate. In a multilateral architecture where the climate regime itself requires consensus, that procedural anchoring in a majoritarian forum is exactly what Vanuatu and the cross-regional core group will be aiming for.
3. The resolution initially contained a proposal for an International Register of Damage â a mechanism to track losses and damages suffered by climate-vulnerable countries. Can you explain what that would have meant in practice, and why it didnât make it into the final text?
The Register of Damage in the zero draft was conceived as a structured, transparent international record of losses, injuries and harms attributable to anthropogenic climate change. The drafters were not improvising: the model is the Register of Damage caused by the aggression of the Russian Federation against Ukraine, established by the General Assembly in November 2022 with administrative support from the Council of Europe. The premise, quite a sound one in our view, is that documentation must precede adjudication. An authoritative evidentiary inventory would render the eventual pursuit of restitution, compensation and satisfaction substantially more tractable, whether through inter-state proceedings under Article 36 of the ICJ Statute, through domestic courts, or through political settlements linked to Article 8 of the Paris Agreement and the Loss and Damage Fund operationalised at COP28. The zero draft went further: it asked the Secretary-General to bring forward proposals for a coordinated climate reparation mechanism. Together, these provisions would have begun to build the procedural infrastructure that the law of state responsibility presupposes but does not itself supply.
Why did it not survive? The public record is unusually candid. A coalition of major fossil-fuel exporters mobilised against it; the Trump administration reportedly circulated a dĂ©marche urging governments to pressure Vanuatu to withdraw the resolution altogether. Vanuatuâs climate justice envoy, Lee-Ann Sackett, publicly acknowledged that dropping the Register was a âmajor concessionâ, as was the softening of the explicit language identifying fossil fuel production and licensing as potentially wrongful acts. Paragraph 10 of the adopted text now requests the Secretary-General to report on ways to advance compliance, âwithout prejudice to the legal positions of States and without implying any determination of responsibilityâ. That is a deliberately modest formulation, but it is also a foothold. As the Ukraine experience suggests, instruments of this kind can be constructed incrementally once political conditions permit. The narrative work, what some research describes as the constitution of climate harm as a legally cognisable object, continues, even where particular institutional vehicles are delayed.
4. The resistance from powerful fossil fuel-exporting countries you just mentioned illustrates how difficult it is to reach binding international agreements through traditional multilateral channels. And yet something interesting has just happened: Colombia and the Netherlands convened the First Conference on Transitioning Away from Fossil Fuels in Santa Marta, bringing together 57 countries outside the formal UN climate architecture. Are we witnessing the emergence of a kind of multi-speed international climate governance â where a coalition of willing states moves ahead while others block progress in the established forums?
Santa Marta represents, in our view, a significant innovation in the architecture of international climate governance, and âmulti-speedâ is probably the most honest characterisation. Fifty-seven countries, representing roughly one third of the global economy, with the European Union, the United Kingdom, Colombia, Nigeria, the Netherlands, Brazil, Kenya, the Marshall Islands, Tuvalu, Vanuatu and others in the room, convened deliberately outside the UNFCCC and explicitly framed as a âcoalition of the willingâ. China, Russia, the United States and India were not invited.
There are illuminating precedents in international economic law. The plurilateral track in the WTO, the Environmental Goods Agreement attempt, the structured discussions on plastics pollution, and the Trade and Sustainable Development âfriendsâ groupings operate on a similar logic: when consensus-based multilateralism stalls, like-minded states proceed with deeper commitments while keeping the door open to subsequent accession. Santa Marta inherits some of that logic but applies it to an area where the UNFCCC has historically claimed primacy. The conference produced a Co-Hostâs Statement rather than a negotiated outcome, and established workstreams including: (i) national and regional fossil-fuel phase-out roadmaps, aligned with NDCs; (ii) supply-side measures and transformation of demand (with methane regulation, fossil-fuel subsidy reform, and trade-related tools, including ISDS reform); (iii) producer-consumer financial-system alignment, including the macro-financial and debt dimensions of transition. It also agreed on a Science Panel for the Global Energy Transition. Follow-up is already structured: Tuvalu and Ireland will co-host the second conference in 2027; the synthesis report will feed into the Bonn intersessional, London Climate Action Week, the UN Secretary-General during New York Climate Week, and ultimately into COP31 in Antalya.
Whether this constitutes fragmentation or constructive pluralism depends on how participants manage the relationship back to the formal regime. The genuine risk is that the consensus forum is hollowed while the coalition forum lacks universality. The genuine opportunity is that the coalition demonstrates feasibility, generates supply-side norms, on methane, on ISDS, on fossil-fuel subsidy phase-out and gradually pulls the reluctant state parties along through trade, finance, and reputational pressure.
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5. Looking at both the ICJ advisory opinion and the Santa Marta process together, a picture emerges of international climate law slowly building pressure from multiple directions simultaneously â courts, General Assembly resolutions, coalitions outside the UN framework. But the countries most responsible for historical emissions â above all the United States â are actively working to undermine each of these tracks. Is there a realistic scenario in which this accumulation of legal and political pressure actually changes behaviour, or are we watching an elaborate process that leaves the most powerful actors untouched?
The honest answer requires us to resist both triumphalism and despair. International law operates by accumulation, not by single instruments. Neither the AO, nor the Vanuatu resolution, nor Santa Marta will, on their own, compel the United States or any other major emitters to alter their behaviour against their perceived short-term interest. Anyone promising otherwise is misreading both the legal and political dynamics.
What the accumulation does, however, is more profound. It progressively changes the legal background against which every other actor operates. Domestic constitutional and supreme courts in the Netherlands, Germany, Switzerland, Korea, Brazil and elsewhere have already demonstrated their willingness to use international authority, the IPCC, ITLOS, and regional human rights jurisprudence to discipline their own governments. The unanimous ICJ opinion, with its express findings on stringent due diligence and human rights, gives those courts a substantially firmer anchor. The AO will make it harder to dismiss climate measures as arbitrary regulatory takings in investment cases. The UK Supreme Courtâs Finch judgment on downstream emissions in licensing is part of the same emerging pattern. Even corporate liability litigation, which we had previously assessed with some scepticism on causation grounds, is now developing a more defensible doctrinal footing as attribution science matures.
The right framing, in our view, is the one Marie-Claire and Christina Voigt have recently put forward: international climate law in this period is a matter of courage, contributions and compliance. Courage from states like Vanuatu, willing to lead in the face of dĂ©marches from larger powers. Contributions from coalitions of the willing, Santa Marta, the Powering Past Coal Alliance, the Fossil Fuel Treaty initiative, the High Ambition Coalition. And compliance constructed gradually, through every available channel: judicial, legislative, market, and social. The seven principles of sustainable development law, equity, common but differentiated responsibilities, precaution, public participation, good governance, integration, and the principle of sustainable use, provide the integrative framework within which these strands cohere. The accumulation matters because every legal foothold makes the next one easier to secure. That is not an elaborate process leaving the powerful untouched. It is the only realistic way that an interdependent legal order has ever, in any field, brought powerful actors to heel. In conclusion, once the lawyers move in, you know the problem is serious, and for anyone simply wishing the problem of climate change away, we now have an answer from the worldâs highest court to the worldâs biggest problem. As the ICJ instructed in its last paragraph:
âHowever, the questions posed by the General Assembly represent more than a legal problem: they concern an existential problem of planetary proportions that imperils all forms of life and the very health of our planet. International law, whose authority has been invoked by the General Assembly, has an important but ultimately limited role in resolving this problem. A complete solution to this daunting, and self-inflicted, problem requires the contribution of all fields of human knowledge, whether law, science, economics or any other.â
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Editorâs Pick
by EVA MARIA BREDLER

Donât we all dream of independence? Peace and quiet, a life in our own time. In her visionary novel The Wall (1963), Marlen Haushofer interrogates exactly that notion of individual freedom. The novel takes the form of a journal kept by a woman who suddenly finds herself alone in the world during a mountain trip: while her cousin and her husband head out for the evening, she stays behind at the hunting lodge with their dog. When the couple fail to return the following morning, she sets off down into the valley â and walks into the eponymous invisible wall. The dog bloodies his snout against it. Like a diving bell, the wall seals her off from the rest of the world. We follow her as she works the land and as the animals left behind become her family: a dog, a cat, a cow. I first read the book during the pandemic â and with every reading I find something new in Haushoferâs unsentimental prose, which traces our relationships to nature and to ourselves with quiet force.
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The Week on Verfassungsblog
summarised by EVA MARIA BREDLER
Climate action is moving on multiple fronts, as Marie-Claire Cordonier Segger, Tejas Rao and Markus Gehring explained in our Five Questions. Another case with potentially global implications is currently unfolding in Australia. In Denman â the first climate case to reach Australiaâs apex court â the question is whether the approval of a coal mine should have taken into account so-called Scope 3 emissions: the greenhouse gases released when the extracted coal is burnt. The central legal question is whether global emissions can count as likely environmental impacts âin the localityâ under Australian planning law. NICK SCOTT, HARJ NARULLA, NICHOLAS YOUNG, MICHAEL YOUNG, MICHAEL BURGER, HARRO VON ASSELT, JESSICA WENTZ and MARIA ANTONIA TIGRE (ENG) argue that they should.
In the meantime, the European Parliament has approved the proposed EU Return Regulation, which would massively expand detention. RHEA KUMMER (ENG) calls this the âICE-ification of the EUâs migration policy and the de facto criminalisation of people on the moveâ and exposes where it would violate the ECHR and the EU Charter of Fundamental Rights.
Italy has long been trying to extend EU migration policy â territorially, that is: migrants intercepted at sea are to be processed on Albanian territory under exclusively Italian jurisdiction. Advocate General Emiliou now delivered his Opinion in Sedrata, the first of three cases pending before the CJEU concerning the Italy-Albania Protocol. JONAS BORNEMANN and ELEONORA FRASCA (ENG) analyse the Opinion and explain how the CJEU may be lowering the legal threshold for offshore migration processing under EU law.
In another long-awaited decision, the CJEU declared Hungaryâs anti-LGBTQ law incompatible with EU law â for the first time applying Art. 2 TEU in isolation. LEA DIRKSEN and NOAH THOMASÂ SEYLLER (GER) examine the standards the CJEU has developed in Commission v. Hungary for the âmagic triadâ of essence, dignity, and values â and where that search is only just beginning.
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The US Supreme Court, by contrast, weaponises the language of freedom against legally enshrined values. DUNCAN HOSIE (ENG) takes a critical look at the anti-orthodoxy rhetoric of the Supreme Court. Since Barnette (1943), âorthodoxyâ has functioned in American constitutional law as shorthand for state-imposed belief â the very thing the First Amendment most centrally forbids. Justice Gorsuch invoked the dictum most recently in Chiles v. Salazar to strike down a Colorado prohibition on certain forms of conversion therapy. Hosie argues the rhetoric is conceptually unsound: by collapsing the distinction between authoritarian indoctrination and democratically settled values or expert consensus, it has become a sword rather than a shield, deployed against civil rights enforcement and professional regulation alike.
The question of what the state may legitimately regulate â and how â also animates a debate in France. A new bill proposes replacing the current End-Demand legislation with full decriminalisation of sex work. Crucially, sex workers themselves were involved in drafting the proposal. MARIE-SOPHIE PETERS (ENG) considers this a blueprint for more inclusive democracy and praises the bill as nuanced and detailed.
India struggles with making democracy inclusive in a national sense. As the worldâs largest democracy, it faces a unique challenge in the twenty-first century: managing the relationship between democracy and federalism. SARATH PILLAI (ENG) suggests that the constitutional and political debates in late colonial India on questions of democracy and federalism show a similar face-off â one that fundamentally defined postcolonial Indiaâs broken promise of federalism.
Europe faces another broken promise: since Donald Trumpâs second presidential term, transatlantic relations have fractured, and with them the assumption of American protection. The ALCIDE project now explores the idea of reviving the European Defence Community, whose ratification failed more than seventy years ago â but which, according to some scholars, could yet be completed if Italy and France signed the treaty. Last week, Robert SchĂŒtze criticised the idea as a âlegal fantasyâ. As the senior jurists involved in the ALCIDE project, FEDERICO FABBRINI and FRANZ C. MAYER (ENG) felt compelled to respond.
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Zum 01.09.2026 sind am Max-Planck-Institut fĂŒr auslĂ€ndisches öffentliches Recht und Völkerrecht in Heidelberg
drei PostDoc-Stellen sowie drei Promotionsstellen
â
im Team von Professor Dr. Helmut Aust zu besetzen.
Themenschwerpunkte seiner Forschung am MPIL sind das Kooperationsvölkerrecht in antagonistischen Zeiten, empirisches AuĂenverfassungsrecht sowie die Geographien des Völkerrechts.
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This week, we launched the symposium âOn Law and Politics in the Hungarian Transitionâ (ENG). Emerging from a three-day conference at the Max Planck Institute for Comparative Public Law and International Law, the symposium explores what constitutional repair in Hungary can look like after Tiszaâs landslide victory: For the fifth consecutive election, the winning party has secured a two-thirds majority in the Hungarian parliament. BEĂTA BAKĂ argues the magic of that supermajority was always a lie: it never guaranteed compromise. PĂL SONNEVEND makes the case against a new constitution. Drawing lessons from Poland, ADAM BODNAR insists that rebuilding institutions in Hungary is not enough: accountability requires committed prosecutors and patient voters. ANDRĂS JAKAB identifies blind spots in the current discourse on transitional justice and outlines what a post-hybrid transitional justice framework would need to look like.
Be it constitutional or climate repair: the world needs collective action, confidence, and creativity. As Vanuatuâs climate minister, Ralph Regenvanu, said at a briefing earlier this month: the UNâs initial resolution was âa collective act of multilateral confidence that law can help steer us through the climate crisisâ. The ICJ shared that confidence â unanimously. Let us hope the states catch the spirit.
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Thatâs it for this week. Take care and all the best!
Yours,
the Verfassungsblog Team
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The post âOnce the Lawyers Move In, You Know the Problem Is Seriousâ appeared first on Verfassungsblog.


