Strengthening the Global Response to Climate Change and Sustainable Development: Reflections on the ICJ's Advisory Opinion

Abstract

This contribution examines how the International Court of Justice (ICJ) approached the principle of sustainable development in its 2025 Advisory Opinion on Obligations of states in respect of climate change. The principle requires states to balance environmental, social and economic considerations so that both present and future generations can satisfy their basic needs. Yet, it offers little guidance on how this should be done. The Court was thus in a unique position to clarify how the balancing exercise should be conducted in the context of one of the international community's most pressing challenges, namely the fight against climate change. Although the Court did not engage with the principle in detail, this contribution argues that sustainable development underpins core determinations in the Advisory Opinion.

Introduction

In its 2025 Advisory Opinion on Obligations of states in respect of climate change, the International Court of Justice (ICJ) was faced with the challenging task of defining states’ obligations in the context of the fight against climate change. For this purpose, the Court drew on a large number of international treaties as well as on customary international law and, at the request of participants in the proceedings, certain “other principles”. ¹ The principles referred to include sustainable development, common but differentiated responsibilities and respective capabilities, equity, intergenerational equity, the precautionary approach or principle, and the “polluter pays” principle.

This contribution zooms in on the principle of sustainable development, which today functions as a guiding principle for environmental action. ² Sustainable development essentially seeks to balance the needs of the present generation with those of future generations. ³ The principles of intragenerational equity – a fairer distribution of both benefits and burdens within the current generation – and intergenerational equity – referring to the need to safeguard the resource base for development for future generations – are central to sustainable development. The principle is furthermore generally considered to contain three dimensions, relating to the economy, society and the environment. ⁴ These dimensions must be balanced with each other as part of decision-making, guided by the principles of intra- and intergenerational equity as the overarching objectives of sustainable development.

Sustainable development: birth and evolution

Notwithstanding its popularity in practice, sustainable development has been controversial from its inception. When it was introduced in the 1980s, it was meant as a compromise for reconciling the priorities of newly-independent states to promote economic growth and those of industrialized states to reduce environmental degradation caused by their development trajectories. ⁵ As a compromise principle, sustainable development has been criticized for being a “metafix” ⁶ and a “diplomatic trick”, ⁷ a model that appeals to everyone precisely because no-one can disagree with its core, while masking great controversies about the choices and trade-offs that need to be made in practice.

Indeed, the balancing exercise required by sustainable development does not prescribe a particular outcome. States are merely required to integrate the economic, social and environmental dimensions of sustainable development in their decisions, but what this means in practice is not self-evident. ⁸ Science can play an important role in determining the (minimum) standards for environmental protection, but this still leaves states with ample opportunities to prioritise short-term (economic) benefits over long-term environmental goals. The role of technology is furthermore ambiguous: it is both an enabler and a deterrent. It plays an important role in enhancing sustainability, but it can also disincentivise states to take urgent environmental action, based on a mistaken belief that future technologies will magically solve the environmental problems that we are facing today.

Given the open-ended nature of sustainable development, the Court was in a unique position to provide guidance on how the principle should be interpreted in the context of one of the core challenges of our time, namely the fight against climate change. This challenge epitomises the dilemma that is at the core of sustainable development: how to reconcile the pursuit of economic development – and the energy use that drives it – with the urgent need to preserve the stability of the Earth's climate system, which sustains life on Earth now and in the future?

This contribution examines the approach taken by the Court in its Advisory Opinion on climate change. For this purpose, it first briefly sketches how the principle has been conceptualised in the UN climate regime and discusses the various ways in which states participating in the proceedings have interpreted it. This will be followed by an analysis of the ICJ's engagement with the principle throughout its case law, with particular emphasis on its Advisory Opinion on climate change. It will show that – even though the Court did not discuss the principle at length – it underpins core determinations in the Advisory Opinion.

The climate change regime and sustainable development

Sustainable development figures prominently in the UN climate change regime, ⁹ consisting of the 1992 UN Framework Convention on Climate Change (UNFCCC) as the foundational treaty and the 1997 Kyoto Protocol and the 2015 Paris Agreement as subsequent agreements that develop the obligations contained in the UNFCCC. The prominent role that sustainable development plays in the UN climate regime is no surprise, as this regime evolved in parallel with the principle of sustainable development. The UNFCCC was negotiated around the time sustainable development materialised in international policy, most importantly through the 1992 Rio Declaration on Environment and Development and Agenda 21. The 2015 Paris Agreement, in turn, was negotiated in parallel with Agenda 2030, which includes the Sustainable Development Goals (SDGs). ¹⁰

A first mention of sustainable development can be found in the preamble to the UNFCCC, where parties recognize that “all countries, especially developing countries, need access to resources required to achieve sustainable social and economic development”. ¹¹ According to the preamble, this goal can only be achieved through a growth in the energy consumption of developing countries, while taking into account the possibilities of energy efficiency with the aid of new technologies. Sustainable development is further included in Article 3 of the UNFCCC, which lists the principles that – as clarified in the chapeau – guide states’ actions under the Convention. More specifically, Article 3(4) states that “[t]he Parties have a right to, and should, promote sustainable development.” This formulation is based on a compromise between developed countries, which wished to emphasise a duty to promote sustainable development, and developing countries, which sought recognition of the right to development, as set out in the 1986 Declaration on the Right to Development. ¹² Article 3(4) of the UNFCCC further refers to the need to tailor measures to the specific conditions of each state party and to integrate climate policies and measures in national development programs, “taking into account that economic development is essential for adopting measures to address climate change.” Lastly, Article 3(5) emphasises the need for states to cooperate on “promot[ing] a supportive and open international economic system that would lead to sustainable economic growth and development in all Parties, particularly developing country Parties, thus enabling them better to address the problems of climate change.”

Sustainable development is, therefore, conceptualised in the UNFCCC alternatively as an objective, a right and a duty for states. As will be shown in the following sections, one of the questions that surfaced in the proceedings concerned the interpretation of the right to promote sustainable development. Furthermore, promoting economic development through reform of the international economic system is regarded as a precondition for effective climate action, while (improving access to) new technologies is conceived as a way to reconcile economic growth with climate action. The focus in the UNFCCC is therefore on the economic dimension of sustainable development and on the special position of developing countries.

The 1997 Kyoto Protocol adopts a different perspective. Sustainable development is referenced in Articles 2 and 10 as an objective to be achieved through sector-specific reforms, data collection, technology transfer and international scientific cooperation. The emphasis therefore shifted from development to sustainability. This is however not a true shift in the sense that Article 2 of the Kyoto Protocol – which contains measures for reforms in sectors such as agriculture and transport – exclusively addresses developed countries, which – according to Article 3(1) of the UNFCCC – should take the lead in combating climate change. As for Article 10 of the Kyoto Protocol, which applies to all parties, its ambit is limited to data collection, technology transfer from developed to developing countries and international scientific cooperation. Furthermore, specific reference is made to the principle of common but differentiated responsibilities and the specific national and regional development priorities, objectives and circumstances of state parties to the Kyoto Protocol. While the focus in the Kyoto Protocol is therefore on the environmental dimension of sustainable development, it addresses the economic and social dimensions through (radical) differentiation and by referencing developing countries as the primary beneficiaries of technology transfer.

Finally, the 2015 Paris Agreement includes abundant references to sustainable development, which can be explained by the parallel negotiations of the Sustainable Development Goals (SDGs). ¹³ A first reference can be found in the preamble, which emphasises “the intrinsic relationship that climate change actions, responses and impacts have with equitable access to sustainable development and eradication of poverty”. ¹⁴ It thereby underscores the various ways in which climate change measures and impacts interact with sustainable development. This is particularly important from the perspective of developing countries, who often suffer the most from the impacts of climate change, while having contributed little to its causes. Sustainable development is further referenced in Articles 2, 6, 7 and 8 of the agreement. ¹⁵ Article 2 is a key provision, as it sets out the objective of the Agreement, namely “to strengthen the global response to the threat of climate change, in the context of sustainable development and efforts to eradicate poverty”. ¹⁶ Sustainable development is therefore conceived in Article 2 of the Paris Agreement not as an objective or a right, but rather as the context within which the global response to climate change should be made effective. It affirms the importance of embedding climate action in a broader strategy that pays due attention to all three dimensions of sustainable development and the different positions and capacities of state parties. It goes without saying that this may mean different things for different states and may therefore also lead to a variety of interpretations of this provision. This is also clearly visible in the statements submitted by the participants in the proceedings, to which I will turn next.

ICJ AO proceedings: interpretations of sustainable development

The ICJ's Advisory Opinion (AO) proceedings on Obligations of States in Respect of Climate Change, arising from the UN General Assembly request, ¹⁷ were characterised by an unprecedented level of participation. ¹⁸ Over ninety written statements were submitted to the Court and over a hundred states and international organizations participated in the oral proceedings. Many participants submitted their views on the interpretation of the principles of law that guide states’ actions with respect to climate change. Several engaged directly with the principle of sustainable development, while others focused on the related principles of equity and common but differentiated responsibilities and respective capabilities (CBDR-RC). ¹⁹

The participants in the ICJ AO focusing on related principles nevertheless referred to the principle of sustainable development. The EU, for instance, underscored in its written submission that the principle of intergenerational equity is “an “integral element” of the broader principle of sustainable development”. ²⁰ It further stated that “the ultimate objective of the right to development” is “meeting “developmental and environmental needs of present and future generations””, as set out in Principle 3 of the Rio Declaration, and – referring to the IPCC - that “intergenerational equity “underlies the concept of sustainability” and is an “intrinsic component” of sustainable development.” ²¹ Likewise, the Democratic Republic of the Congo argued that “States must impose restrictions on the activities of today's generations that are undermining respect for the rights of future generations, in particular their right to life and a healthy environment, which also results from the principle of sustainable development.” ²² Lastly, reference can be made to Micronesia, a small-island developing state (SIDS) that is highly vulnerable to the impacts of climate change. Micronesia referred to sustainable development to make the case that – even though international law has not explicitly defined intergenerational equity – this principle is reflected in international instruments relating to sustainable development, including the 1972 Stockholm, 1992 Rio and 2012 Rio+20 Declarations. ²³ It further referred to the need “to promote harmony with nature” “to achieve a just balance among the economic, social and environmental needs of present and future generations”. ²⁴

Most of the participants that directly engaged with sustainable development focused on interactions between the three dimensions of sustainable development. Relevant statements referred to differences in the social and economic circumstances of states, either as a foundation for differentiation in mitigation obligations [Article 3(4) UNFCCC] or as a basis for financial and technical assistance in the implementation of the obligations under the UN climate regime [Article 4(3)-(7) UNFCCC]. As to the latter, Colombia, for instance, emphasized the need for collective action with respect to the means of implementation of the climate regime. In doing so, it highlighted the potential for trade-offs to occur between climate action and sustainable development, due to the high costs involved in both. ²⁵ Likewise, China argued that “developing countries’ implementation of commitments depends on developed countries’ effective meeting of their obligations regarding means of implementation.” ²⁶ In the same vein, the Indian written statement underscored that “[f]ulfilment of obligations by the developed countries, including providing the means of implementation and support, are critical enablers for developing countries to take effective climate action. Any fair or meaningful assessment of obligations of States cannot, therefore, be conducted without simultaneously assessing the support provided.”. ²⁷ Finally, Indonesia highlighted the need for “increased international co-operation including improved access to adequate financial resources, particularly for vulnerable regions, sectors and groups” as a primary enabler for advancing sustainable development for all. ²⁸

As to differentiation in mitigation obligations, a key concern voiced by several participants concerned the balance between climate action on the one hand and social and economic needs of developing countries on the other. The African Union, for instance, argued for “a legal framework that imposes more stringent obligations on historically high emitters and enables developing countries to pursue sustainable development pathways”. ²⁹ It also firmly connected the right to development, considered central to states’ obligation to protect the climate system, ³⁰ to the notion of sustainable development. It posited that the right to development “is to be understood in light of the well-established concept of sustainable development, and thus needs to be fulfilled so as to “enable economic development to proceed in a sustainable manner””, referencing Article 2 of the UNFCCC. ³¹ India, in its written statement, contended that “developing countries deserve equitable access to the total carbon budget in the pursuit of their climate goals, while simultaneously pursuing sustainable development and poverty eradication.” ³² In its oral statement, it likewise emphasized “the right to promote sustainable development”, set out in Article 3(4) of the UNFCCC, as a core principle guiding the implementation of the UNFCCC. ³³ It further placed significant emphasis on the historic responsibility of developed countries, recognized in the preamble of the UNFCCC, as a basis for differentiation. ³⁴ It finally requested the Court to consider that “[t]he UNFCCC and its two instruments aim to strengthen the global response to the threat of climate change in the context of the overriding priorities of developing countries, which continue to remain poverty eradication and sustainable development.” ³⁵

Finally, China engaged extensively with the principle of sustainable development in its written statement to argue for differentiation and recognition that the overriding needs of developing countries lie in poverty eradication and economic development. While recognizing that sustainable development “is the fundamental goal of human beings in tackling climate change and its adverse effects, which requires relevant climate actions to promote sustainable development”, ³⁶ it ascribed “multiple meanings” to the principle of sustainable development. ³⁷ Referring to Article 3(4) of the UNFCCC and Article 4(1) of the Paris Agreement, it stated that the principle “requires all Parties to take an integrated and coordinated approach to promote social and economic development and [to avoid the adverse impacts of] climate change”. ³⁸ In China's view, this implies that “measures and actions taken in addressing climate change should provide synergistic benefits, maximizing environmental, social and economic benefits.” ³⁹ A second meaning that it ascribed to the principle of sustainable development concerns respect for the right to development, which includes “supporting the realization of the right of all human beings to an adequate living standard and the equitable distribution of the benefits thereof.” ⁴⁰ Third and last, China argued on the basis of the preambular language of the UNFCCC that the principle of sustainable development requires “to take the legitimate priority needs of developing countries for sustained economic growth and eradication of poverty into consideration.” ⁴¹ According to China, this means in practice that “[t]he “luxury emissions” of developed countries should be ceased, whereas the “survival emissions” and “developmental emissions” of developing countries should be guaranteed. ⁴² It reiterated this point in its oral statement when it argued that “[e]conomic development and poverty eradication are the legitimate priority needs of developing countries” and that “[t]his includes ensuring access to resources and acknowledging their energy consumption must increase.” ⁴³ These statements invoke the idea of a ‘right to emit’ for developing countries, based on developed countries’ historical responsibilities and differences in capacities between developed and developing countries. This idea was underscored by several participants in the proceedings, ⁴⁴ while others, including several developing countries, criticized this approach. ⁴⁵

The abovementioned references to the positions taken by various states in written and oral statements in the ICJ AO proceedings reinforce the view that the principle of sustainable development is multifaceted. Most of the participants invoked it alternatively as an objective of climate action, as a right and as an obligation. They furthermore connected it to several other principles included in the climate regime, most importantly the principles of (intergenerational) equity and CBDR-RC, and to human rights, including the right to development and the rights of future generations. Furthermore, while all participants recognized that urgent climate action is necessary, they provided different views on how such action should be balanced with social and economic development. The ICJ was thus in a unique position to provide clarification on how this balancing exercise should be conducted in the context of the fight against climate change.

The ICJ opinion on sustainable development

This section examines the approach taken by the Court with respect to the principle of sustainable development in its AO on climate change. Before doing so, it is however relevant to note that this was not the first opportunity for the Court to engage with the principle of sustainable development. This principle figured prominently in two contentious cases before the Court involving the management of shared water resources. These are the Court's judgments in the case concerning the Gabčíkovo-Nagymaros Project on the one hand and the case concerning Pulp Mills on the River Uruguay on the other. The case concerning the Gabčíkovo-Nagymaros Project was triggered by Hungary's withdrawal from a treaty with Slovakia concerning a joint hydroelectric project on the Danube, which, according to Hungary, posed a threat to the river and its environment. It was brought before the ICJ in 1993, only one year after the principle of sustainable development had found formal recognition in the Rio Declaration on Environment and Development and in the Rio Conventions.

Cognisant of the fact that sustainable development had not yet fully matured in international law, the Court referred in its 1997 judgment to the “concept” of sustainable development and defined it as “the need to reconcile economic development with protection of the environment”. ⁴⁶ Furthermore, it emphasised the importance of inter-state cooperation, ordering the parties to “look afresh at the effects on the environment of the operation of the Gabčíkovo power plant”, ⁴⁷ while specifying that “it is not for the Court to determine what shall be the final result of these negotiations to be conducted by the Parties.” ⁴⁸ According to the Court, “it is for the Parties themselves to find an agreed solution that takes account of the objectives of the Treaty, which must be pursued in a joint and integrated way, as well as the norms of international environmental law and the principles of the law of international watercourses.” ⁴⁹

Thirteen years later, the Court had the opportunity to expand on its previous judgment in the case concerning Pulp Mills on the River Uruguay, which was brought by Argentina in relation to Uruguay's unilateral authorisation of the construction of two pulp mills on the Uruguay River, the natural border between the two states. In its judgment, the Court reaffirmed the central role of the principle of cooperation in the context of sustainable development. It referred back to its determinations on sustainable development in its judgment concerning the Gabčíkovo-Nagymaros Project and considered that “it is by co-operating that the States concerned can jointly manage the risks of damage to the environment that might be created by the plans initiated by one or other of them, so as to prevent the damage in question, through the performance of both the procedural and the substantive obligations laid down by the 1975 Statute.” ⁵⁰ The Court furthermore referred to the “need to strike a balance between the use of the waters and the protection of the river consistent with the objective of sustainable development” ⁵¹ and confirmed that it is the “balance between economic development and environmental protection that is the essence of sustainable development.” ⁵²

Three observations can be drawn from these cases. First, the Court referred to sustainable development alternatively as a “concept” and an “objective”, with neither of these designations carrying much legal weight. ⁵³ Second, the Court emphasised the importance of interstate cooperation in both judgments, making it a primary modality for conducting the balancing exercise between economic development and environmental protection that is - according to the Court - the essence of sustainable development. Finally, the Court confined the balancing exercise to the economic and environmental uses of a shared resource, without taking into consideration social uses. ⁵⁴

The Court built on this previous case law yet also departed from it in its Advisory Opinion on Obligations of states in respect of climate change. Most notably, like in its previous case law, the Court defined sustainable development as the “need to reconcile economic development with protection of the environment” and connected it to interstate cooperation for the protection of the environment. ⁵⁵ The most important change compared to its previous case law concerns the legal status that the Court attached to sustainable development. In its Advisory Opinion, the Court recognized that sustainable development is both a guiding principle in the context of the UN climate regime and a general principle of law. As to the latter, the Court considered that the principle of sustainable development “has also been developed independently of treaties” and that it enjoys “continuous and universal recognition”. ⁵⁶ From the perspective of sources, the Court thus implicitly recognized sustainable development to constitute a general principle of law under Article 38 of its Statute. ⁵⁷

The dual nature of sustainable development as a guiding principle under the UN climate regime and a general principle of law has implications for the functions that it is considered to perform in relation to the fight against global warming. Within the UN climate regime, the Court identified the principle's primary function as guiding the interpretation of treaty obligations. ⁵⁸ More specifically, the Court was of the view that “the principle of sustainable development does not in itself create specific rights and obligations for States” but rather that it “informs the interpretation of the obligations under the climate change treaties”. ⁵⁹ Importantly, as emphasized by Judge Xue in her Separate Opinion, the fact that the principles are to guide the parties implies that they are binding on them and that the principles therefore “apply throughout the Framework Convention and to the subsequent agreements forming part of the climate change treaty régime”. ⁶⁰ Unfortunately, the Court did not provide further guidance on how the principle of sustainable development informs the interpretation of the obligations under the climate change treaties, a lacuna that was addressed by Judge Xue in her Separate Opinion. In essence, Judge Xue interpreted the principle of sustainable development as requiring states to adopt an integrated approach towards climate action, taking into consideration all three dimensions of sustainable development in the implementation of their obligations under the UN climate regime. Importantly, such an integrated approach is firmly embedded in multilateralism, including through reforming the international economic system and by pursuing synergies between the UN climate regime and the UN Sustainable Development Goals, ⁶¹ an issue that was not addressed by the Court, but which is of essence in practice.

Whereas the Court therefore offered little detail on how the principle of sustainable development informs the interpretation of states’ obligations under the UN climate regime, it was equally non-committal regarding the broader functions that the principle of sustainable development performs as a general principle of law. It did clarify though that its function as a general principle is not confined to the interpretation of treaties – whether it concerns the treaties that compose the UN climate regime or other (environmental or human rights) treaties – but that it also “guides […] the determination of rules of customary international law, including the duty to prevent significant harm to the environment and the duty to co-operate for the protection of the environment”. ⁶² In this way, the principle of sustainable development not only assists in interpreting existing treaty obligations but also contributes to shaping the substance of customary norms that underpin the international legal response to climate change. Since the Court specifically referred to the duties to prevent and to cooperate, the remainder of this section will focus on the Court's approach to these customary obligations and the role that sustainable development plays therein.

As for the duty of prevention, the Court qualified it as a due diligence obligation based on a “stringent” standard, requiring “a heightened degree of vigilance and prevention”. ⁶³ As for its substance, the Court clarified that it consists of several elements, including “States taking, to the best of their ability, appropriate and, if necessary, precautionary measures, which take account of scientific and technological information, as well as relevant rules and international standards, and which vary depending on each State's respective capabilities [as well as…] undertaking risk assessments and notifying and consulting other States, as appropriate.” ⁶⁴ The Court further considered that, in the context of climate change, states’ respective capabilities must be determined on the basis of their national circumstances and not merely on their status as developed or developing country. Based on this objective test, the requirements of diligence are heightened “as States develop economically and their capacity increases”. ⁶⁵ Even though not addressed by the Court, this approach has implications for the balancing exercise that is inherent in sustainable development: the actual circumstances of states and not their (self-designated) status as developed or developing will determine how they should balance between economic development and environmental protection.

As for the duty of cooperation, the Court expressly invoked the principle of sustainable development, noting that “sustainable development is furthered through close and continuous co-operation in the context of climate change”. ⁶⁶ The Court also clarified the interconnections between the duties to cooperate and to prevent. It reasoned that the duty to cooperate is “intrinsically linked to the duty to prevent significant harm to the environment, because uncoordinated individual efforts by States may not lead to a meaningful result.” ⁶⁷ In the context of climate change, the Court placed further emphasis on the customary nature of the duty to cooperate by affirming that it is a legal obligation for all states that applies independently from specific commitments made under the UN climate regime. ⁶⁸ Significantly, the Court stated that “[t]he duty to co-operate is founded on the recognition of the interdependence of States, requiring more than the transfer of finance or technology, in particular efforts by States to continuously develop, maintain and implement a collective climate policy that is based on an equitable distribution of burdens and in accordance with the principle of common but differentiated responsibilities and respective capabilities.” ⁶⁹

Taking all these elements into consideration, the functions of the principle of sustainable development in relation to the duties to prevent and to cooperate can be construed as follows. First, sustainable development provides substantive meaning to the duty to prevent, by recognizing that the stringent standard of states’ due diligence obligations is shaped both by environmental objectives and by their socio-economic circumstances. In other words, the reconciliation of environmental protection and economic development needs is at the core of the duty to prevent, conceptualized through the principle of CBDR-RC. Second, sustainable development defines the framework within which the duty to prevent must be exercised. Because climate change cannot be effectively addressed through unilateral action, prevention acquires a collective dimension: sustainable development becomes both the objective of cooperation and the standard guiding each state's individual contribution to preventing global warming within this collective effort. In this way, sustainable development guides both the process and the outcome of states’ concerted efforts to prevent global warming.

Conclusion

Climate change is in essence a sustainable development concern: it is caused by economic development and it can only be addressed through an “urgent system-wide transformation”. ⁷⁰ The good news is that, according to the latest Emissions Gap Report, the required technologies to considerably accelerate climate action are available. ⁷¹ An effective response therefore hinges on states effectively implementing their obligations under international law, based on an approach that is ambitious yet grounded in notions of justice and fairness. The ICJ's Advisory Opinion on Obligations of states in respect of climate change has greatly contributed to clarifying states’ obligations in this regard, most importantly through the holistic approach that it adopted with respect to the applicable law.

Even though the Court offered little detail on how sustainable development informs states’ obligations with respect to climate change or how it interacts with the principles of equity and CBDR-RC, it nevertheless made several determinations that help clarify the functions that sustainable development performs in this context. In particular, the Court indicated that sustainable development – as a general principle of law – guides the determination of the duty to prevent significant environmental harm. This arguably includes informing the standard of due diligence applicable to each State. It further clarified that climate action is made effective through cooperation aimed at achieving sustainable development. This emphasis on multilateralism is significant, as it underscores the need for collective efforts, including by providing support to developing countries in enhancing their capacities to curb climate change. Furthermore, with sustainable development being the ultimate objective of collective climate action, the latter must be firmly embedded in an integrated approach that seeks to generate synergies between environmental, social and economic objectives.

The UN climate regime, other treaties, customary international law and general principles together form the legal foundation of states’ obligations with respect to climate change. The Advisory Opinion on Obligations of states in respect of climate change contributes significantly to clarifying the scope and content of these obligations. At the same time, however, an exclusively legal perspective may not be sufficient. As Judge Xue rightly emphasised in her Separate Opinion, climate action must also be situated within the policy-oriented sustainable development agenda. This wider framework reinforces the centrality of international cooperation: the Sustainable Development Goals identify global partnership as a core means of implementation, most clearly reflected in SDG 17, which calls for strengthened cooperation to achieve sustainable development. Significantly, the SDGs are considered “integrated and indivisible”, ⁷² calling for a synergetic approach to pursuing sustainable development. The legal and policy frameworks therefore reinforce one another: meaningful progress on climate change will require that states interpret and implement their legal obligations through a cooperative approach that fosters synergies between development and environmental protection, grounded in equity and CBDR-RC. The SDGs provide a lens through which states can assess how such synergies can be achieved. In doing so, the SDGs complement the international legal framework, helping states to anchor their climate responses within a coherent and integrated strategy for sustainable development.