On July 23, 2025, the International Court of Justice (ICJ) issued a landmark advisory opinion concerning states’ legal duties regarding climate change. Responses initially delved into a variety of implications (possibility of climate harm monetary liability of nations for actions including by their private sectors, the further embedding of the legitimate authority of the IPCC, and the court’s articulation of a stringent due diligence standard). Beyond the concrete, the opinion signals a paradigmatic shift in international environmental law toward a networked, system-based jurisprudence.
The culmination of a six-year campaign initiated by the Pacific Island Students Fighting Climate Change (PISFCC), the opinion has been hailed as an historic turning point in climate justice and accountability. The Court’s concluding remarks starkly highlighted both the legal and extra-legal problem when it situated climate change as “an existential problem of planetary proportions.” Implicitly, this illustrates the court’s awareness that a commanding legal system abstracted from the complex web that shapes climate outcomes, if not disrupted, will fail.
The Intergovernmental Panel on Climate Change (IPCC) has long emphasized that resilience depends on co-locating people and ecosystems and safeguarding ecological functions “at the planetary scale.” The ICJ AO works to translate this into the legal domain.
For decades, environmental law revolved around two familiar paradigms. The first is top-down regulation facilitated by centralized control presuming linear policy causality. The second is market-driven and behavioral; using economic incentives to internalize environmental costs and implementing carbon cap and trade programs. Each approach has yielded some progress but problematically treat the environment like a machine—legal instruments being the machine’s external control mechanism. This assumption has incorporated an understanding of the environment as a singular whole with identifiable and distinguishable parts, each of which may be governed with a knowable causal effect on the whole. For the most part, this excludes complex synergisms and decentralized knowledge centers.
Legal academia has long emphasized siloed legal regimes through landesjurisprudenz, treating systems as internally coherent and largely independent, only occasionally highlighting otherwise as with U.S. law’s inheritance from English common law. International legal principles such as sovereignty discard the need to deconstruct this fragmentation.
But legal systems are not unassailably bounded. Much ink has been spilt analyzing the extent seemingly divergent systems couple, integrate and inform one another through communication. Today, climate change, globalization, and modern complexity expose the limits of viewing law as isolated silos. The world as a machine rhetoric no longer holds.
From Centralized Command to Polycentric Governance
Elinor Ostrom developed the thesis of polycentric governance where decentralized institutions, through diverse stakeholdership, manage shared resources at multiple levels and scales which works toward contextual stage-setting for human-environment self-organization, less the ills of the commons. Polycentric systems create multiple centers of decision-making, from local communities to international organizations, linked by shared goals but responsive to local contexts.
Discourses of the environment have for a long time regarded complex networks to be a fitting signifier: ecology. The world, too, in a common imagination, has come to be seen as a complex network. Legal discourses began to follow suit almost a decade ago with the Paris Agreement. The Paris Agreement, adopted by 195 Parties to the United Nations Framework Convention on Climate Change (UNFCCC), entrusted power at the national level, instigating a polycentric, bottom-up regime which brought both wider support and ambition, but oft without substantive enforcement.
The decentralization of environmental law was the first step in moving toward a legal system that reflects the ecology that it is communicating with. Additionally, the focus on climate change within environmental policy signaled a new understanding of what was to be regulated; the object ‘the environment’ or the dynamic and adapting ‘climate.’
The ICJ AO in its treatment of the Paris Agreement has taken us one step further, keeping power decentralized whilst adding greater accountability and conduct requirements. And, the AO utilizes an array of legal precedent not universally accepted as part of the environmental law regime. The court has reframed the law in ecological terms.
An Unfolding Jurisprudence of Feedback Loops and Systemic Integration
The ICJ’s opinion itself is not legally binding under Article 59 of the Court’s Statute, but each individual element is binding in that the court is restating what the law already is. Important, then, is the court’s treatment of lex specialis—the doctrine that more specific rules override general ones. In finding general State responsibilities under international law permanently apply, it rejected the doctrine brought by several major greenhouse gas (GHG) emitting states (including the United States). Perhaps on its face this is basic administration, a choice of statutory interpretation, but that choice is incredibly consequential.
The Court aligned itself with systemic integration: the idea that specific treaties do not exist in isolation but interact with customary norms, state practices and general principles to create a composite web of obligations. This approach moves away from a siloed international jurisprudence toward one that engages the interdependence of the climate system. Environmental law is not alone in defragmenting other regimes to appreciate state responsibilities. This change has broader consequences for international jurisprudence, but the integration of science, here, makes the legal integration more pronounced.
This critical overlay can help us understand how the international environmental law systems of enforceable and unenforceable rules, norms, prescriptions and overlapping power centers, are constitutive of our perception of climate solutions. Additionally, the direct use of, specifically, IPCC scientific knowledge show that the legal structures and apparatuses are part and parcel of the environmental system.
Systemic integration dislocates opposing theses: unity and fragmentation. A complementary discourse, Earth Law, has unpacked this narrative. Ecological jurisprudence gives primacy to relationships and communication, and the contingency of their production.
A successful climate resilient system will encompass the natural and the extra-natural and will be feedback rich. It will be realized and reproduced through its interactions and feedback loops. The ICJ AO is part of law’s recursive, reproductive, feedback loop. Advisory opinions influence treaty negotiations, state practice, and future litigation—all of which, in turn, reshape the normative landscape. Law is not static text but a dynamic network, continually reproducing itself through interactions among courts, governments, civil society, and scientific bodies. Whilst not etching the substance of such customs, it is translating environmental noise into comprehensible legal obligation.
In keeping with Paris precedent, by emphasizing the polycentricity of climate obligations, the opinion reinforces that global norms and duties must coexist with the local and national regimes and ecologies. The AO displayed a humility once rare in international governance. It said: our systems reduce internal complexities to further define themselves, but to solve problems of scale authority must be both polycentric and adaptive. In practice a non-uniform but coordinated effort exists where we find ecologically literate city plans, honest and responsible private eco-certification schemes, and the integration of traditional ecological knowledges in the transformation of the eco-legal system.
Polycentric and Systemic Integration of Customary International Law
Looping back to the Court’s handling of how diplomatic and normative laws intersect, a concrete materialization of a polycentrically governed complex network that rejects the supremacy of international treaties is raised in its treatment of customary international law. This includes duties to take appropriate, substantial and sustainable measures to prevent harms.That duty is to be achieved cooperatively and diligently. The Court extended the application to the context of climate change. Tangibly, this means treaties and customs reinforce each other, and that states’ practices and customs should be used as guidance in how treaties should be understood as well as giving rise to new obligations; see paragraph 312 of the Advisory Opinion. Plainly, this co-constitutive relationship already feeds into how normative and customary international legal obligations of states are formalized.
The ICJ opinion marks a relational and ecologically in-tune milestone that imperatively moves the international community toward a jurisprudential network adjacent to and interconnected with the rapidly increasing climate emergency. The outburst of critically positive responses from the environmental law community insists the importance of the opinion. The lack of acknowledgement from states who wish not to be held accountable in NDC 3.0s, in the UN General Assembly (who requested the opinion), and at COP 30, speaks equally loudly.