Introduction
On 23 July 2025, the International Court of Justice (ICJ) delivered its advisory opinion on States’ obligations to protect the global climate system, following a request from the United Nations General Assembly. Although advisory opinions are not legally binding, this decision carries considerable authority because it consolidates interpretative trends that had already emerged in international scholarship and litigation.
The opinion is significant for three reasons. First, it confirms that States have obligations of mitigation, adaptation, and, where appropriate, reparation that derive not only from climate treaties but also from customary international law, general principles of international law, and human rights obligations. Second, it treats climate change not as an exceptional legal issue but as an ordinary matter of general international law. Third, it suggests that continued public support for fossil fuels may, in certain circumstances, amount to an internationally wrongful act.
The question submitted to the Court was straightforward: what obligations do States have under international law to protect the climate system and the environment from anthropogenic greenhouse gas emissions for the benefit of present and future generations? Yet behind this apparently simple question lies a broader issue: how climate obligations affect State sovereignty and domestic decision-making.
This blog argues that the Court’s interpretation of climate due diligence has implications that extend well beyond international law. By strengthening the substantive content of climate obligations, the opinion contributes to a progressive transformation of administrative discretion within domestic legal systems.
Climate Due Diligence in International Law
For many years, the duty of climate due diligence was regarded as a highly indeterminate legal obligation. Its practical meaning depended largely on State practice and on the interpretation of climate agreements, particularly the Paris Agreement of 2015. Article 4 of that Agreement introduced Nationally Determined Contributions (NDCs), through which States define their own climate commitments.
The NDC system was intentionally flexible. States were not subject to a strict obligation to achieve specific emissions targets. Instead, they were expected to act diligently by adopting domestic measures capable of pursuing the objectives they had voluntarily declared. Compliance was therefore assessed mainly through procedural criteria: whether a State had adopted plans, regulations, and reporting mechanisms, rather than whether those measures actually produced effective results.
This structure preserved a broad sphere of national discretion. As long as governments could demonstrate that climate-related policies had been adopted, it was difficult to establish a violation of international obligations except in cases of complete inaction. The Paris Agreement reinforced this approach by creating a monitoring framework that focuses primarily on transparency and reporting rather than on substantive review of the adequacy of national commitments.
Against this background, the ICJ opinion does not create entirely new obligations. Rather, it strengthens and clarifies existing principles. Most importantly, it redefines the content of due diligence. The obligation can no longer be interpreted as a merely procedural requirement satisfied by the formal adoption of climate policies. Instead, due diligence must be understood as serving a substantive purpose: preventing, mitigating, and, where necessary, repairing environmental harm.
The Court’s reasoning reflects an evolutionary interpretation of international law. Climate obligations are linked not only to environmental protection but also to the protection of fundamental human rights and to the principle of intergenerational equity. As a result, States are expected to demonstrate genuine consistency between their international commitments and their domestic actions.
From Climate Due Diligence to Administrative Discretion
This development has important implications for administrative law. Traditionally, public authorities have enjoyed significant discretion when adopting planning, regulatory, and authorization measures in environmental matters. Administrative discretion has often been justified by the need to balance competing public interests and to adapt decisions to local circumstances.
The ICJ opinion does not eliminate this discretion. States remain free to choose the instruments through which climate objectives are pursued. However, the opinion narrows the acceptable range of choices by requiring substantive consistency with climate obligations. Administrative discretion can no longer function as a shield protecting public authorities from scrutiny when environmental objectives are systematically undermined.[1]
Consequently, the legality of administrative action can no longer be assessed solely through procedural standards. Courts and reviewing authorities may increasingly examine whether public decisions effectively balance competing interests while giving adequate weight to environmental protection and to the human rights implications of climate change.[2]
Recent climate litigation reflects this trend. Courts have shown growing willingness to recognize forms of judicial protection where inadequate climate action affects citizens’ health, well-being, or fundamental rights. Although judges generally avoid substituting their own policy preferences for those of governments, they have become more willing to assess whether public authorities have respected minimum standards imposed by domestic and international law.
The traditional distinction between political discretion and legal obligation therefore appears increasingly difficult to maintain. Climate governance is progressively shaped by scientific evidence, technical standards, and legally binding commitments. Administrative authorities still make choices, but those choices are exercised within a more constrained normative framework than in the past.
This phenomenon may be described as the “functionalization” of discretion. Public authorities continue to exercise judgment, yet that judgment is increasingly directed toward achieving objectives already defined by law. Climate commitments thus transform discretion from a sphere of political freedom into a mechanism for implementing predetermined legal obligations.
Renewable Energy Communities as a Case Study
A useful example can be found in the development of Renewable Energy Communities (RECs). These initiatives seek to promote the local production and consumption of renewable energy while contributing to broader decarbonisation objectives. Their diffusion often requires planning decisions concerning the location of energy infrastructure, creating potential tensions between environmental objectives and traditional territorial planning interests.
In Italy, this trend is particularly evident in Article 11-bis of Legislative Decree No. 190 of 25 November 2024, which concerns so-called “suitable onshore areas” for renewable energy development. The provision establishes a favourable regime for renewable energy facilities connected with Renewable Energy Communities, exempting them from certain limitations that would otherwise apply to photovoltaic installations.
As a result, the discretionary powers of local authorities in siting decisions are significantly reduced. Territorial administrations operate within a legal framework strongly oriented toward promoting renewable energy production and accelerating the ecological transition.
This legislative choice undoubtedly serves important national and supranational interests. At the same time, however, it may compress local interests traditionally protected through territorial planning, including landscape conservation, urban planning coherence, and the sustainable management of local development.
Italian administrative case law confirms this evolution. The Council of State has increasingly recognized the public interest in maintaining renewable energy facilities not only for energy production but also for their economic, environmental, and social benefits. Similarly, heritage and landscape authorities are increasingly required to conduct genuine balancing exercises rather than relying on automatically conservative approaches.
These developments reflect a broader transformation in the hierarchy of public interests. Environmental protection and ecological transition are no longer viewed as sectoral concerns. They have become central objectives capable of influencing, and sometimes prevailing over, competing public interests.
Towards a Technical-Functional Model of Discretion?
The consequence is a progressive reduction in the practical scope of administrative discretion. Decisions are increasingly guided by objective technical and scientific criteria connected with climate obligations. In many cases, what appears formally as discretionary power operates in practice as a form of technical assessment constrained by predefined legal objectives.
This transformation also has implications for judicial review. Courts traditionally exercise limited scrutiny over discretionary decisions while applying more intensive review to technical assessments. As environmental obligations become increasingly precise, the distinction between discretion and technical evaluation becomes less clear, potentially expanding the scope of judicial oversight.
The current legal framework therefore reveals a strong tendency to prioritize environmental objectives in planning and allocation decisions. Climate due diligence operates not only as an interpretative principle but also as a criterion that shapes the exercise of public power itself.
Territorial planning provides a particularly clear illustration of this process. Increasingly, local decisions are influenced by overriding national and supranational objectives connected with energy security, decarbonisation, and climate protection. Rules facilitating the siting of renewable energy infrastructure demonstrate how traditional planning autonomy may be limited in pursuit of broader public interests.
Ultimately, the ICJ advisory opinion invites reflection on the emergence of a new model of administrative discretion. This model is neither fully political nor entirely technical. Rather, it is a form of technical-functional discretion exercised within a framework increasingly defined by climate obligations, scientific evidence, and human rights considerations.
Conclusion
The significance of the ICJ advisory opinion extends beyond international climate law. By strengthening the substantive content of climate due diligence, the Court contributes to a redefinition of the relationship between environmental obligations and administrative discretion.
States remain free to choose how climate commitments are implemented. Yet that freedom now operates within increasingly narrow legal boundaries shaped by human rights, intergenerational equity, and scientific evidence. The result is a progressive transformation of public decision-making in which environmental objectives acquire greater normative force and administrative discretion becomes increasingly technical and functional in nature.
The emerging challenge for domestic legal systems is therefore not whether discretion survives the climate transition, but how it adapts to a legal framework in which compliance with climate obligations has become a central parameter of administrative legitimacy.
[1] On the subject of due diligence obligations, see: Case of Duarte Agostinho and Others against Portugal https://hudoc.echr.coe.int/eng#{%22itemid%22:[%22001-233261%22]} para. 213-214. The operation of the principle of State due diligence also extends to private individuals, as the Court argued in 2010 in the case Responsibilities and Obligations of States with Respectcavao to Activities in the Area, Advisory Opinion, https://www.itlos.org/fileadmin/itlos/documents/cases/case_no_17/17_adv_op_010211_en.pdf. Recently, the International Tribunal for the Law of the Sea has also expressed itself with an advisory opinion on the subject of diligence always to the principles dictated by the 1982 United Nations Convention on the Law of the Sea, Request for an Advisory Opinion Submitted by the Commission of Small Island States on Climate Change and International Law, Advisory Opinionhttps://itlos.org/fileadmin/itlos/documents/cases/31/Advisory_Opinion/C31_Adv_Op_21.05.2024_orig.pdf tag; Think, for example, of the well-known case submitted to the Supreme Court of the Netherlands, 20 December 2019, Urgenda Foundation v. State of the Netherlands. In literature see. Jacometti 2019, p. 121 ss.
[2] See the order of the Court of Cassation, Sections. Unite, no. 20381 of 21 July 2025, which clarifies that – in the matter of liability for climate change – although it is not allowed, due to an absolute lack of jurisdiction, to “assert a liability of the State legislature for acts, measures or conduct manifestly expressive of the function of political guidance” (and, in the present case, to request the conviction «the adoption of any necessary initiative for the abatement, by 2030, of artificial CO2-ed emissions to the extent of 92% compared to 1990 levels“), it is instead possible to bring a civil action aimed at compensation for the damage caused by climate-changing gas emissions by pollutants (“operating directly or indirectly in the production and distribution of fossil fuels“).
(Photo: Sophia Sideri)
