The International Court of Justice, the UN’s judicial authority, recently ruled that countries are legally obliged to protect and prevent harm to the environment, and that countries must take action to reduce climate change and greenhouse gas emissions. SEI researchers each reflect on the ICJ’s recent ruling.

Multiple Authors

August 4, 2025
6 min read

This piece was originally published on the Stockholm Environment Institute (SEI) website and reflects the perspectives of four SEI researchers: Sara K. Phillips, Emily Ghosh, Dayoon Kim, and Albert Salamanca.

On 23 July 2025, the International Court of Justice (ICJ) – the world’s highest court – ruled that countries are legally obliged to protect and prevent harm to the climate.

Presenting the long-awaited ruling, the ICJ president, Yūji Iwasawa, proclaimed that climate change is an “existential problem of planetary proportions that imperils all forms of life and the very health of our planet”.

What began in 2019 in the Pacific Islands, with a campaign launched by 27 law students, culminated in a landmark advisory opinion on states’ obligations under international law to protect our climate and environment for present and future generations – and importantly the legal consequences if they fail to meet these. Although not legally binding itself, the opinion makes clear that failures by countries to act and protect the climate system would breach the international laws by which they are bound.

With far-reaching consequences for climate and environmental action, four of SEI’s researchers reflect here on the implications of such a ruling: What legal repercussions will it have for countries around the world? Will it underscore the importance of multilateralism and global governance? Can the opinion serve as a springboard for protecting those most at risk from the impacts of climate change?

The ICJ clarifies state obligations on climate change

Sara K. Phillips – SEI US Scientist

The ICJ’s advisory opinion is a welcome and important contribution to international jurisprudence and provides valuable clarity on the interactions between various bodies of international law, including climate change treaties, human rights law, and customary international law. Through a comprehensive mapping of how these bodies of law interact as concerns climate change, the Court has provided a reference point for practitioners in various sectors to better understand state obligations and potential avenues for redress under the international system. Perhaps most poignantly, however, the Court also acknowledges the limits of international law in addressing the climate emergency, noting that:

International law . . . 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 . . . Above all, a lasting and satisfactory solution requires human will and wisdom – at the individual, social and political levels – to change our habits, comforts and current way of life in order to secure a future for ourselves and those who are yet to come.

Key findings of the Court include:

Climate change treaties and other multilateral environmental agreements contain binding obligations for states in relation to protecting the climate system from greenhouse gas emissions.
Customary international law also contains state obligations in relation to protecting the climate system, including (a) the duty to prevent significant harm to the environment by acting with due diligence and in accordance with common but differentiated responsibilities and respective capabilities; and (b) the duty to cooperate in good faith to prevent significant harm.
Climate change impacts human rights, and states have an obligation to respect and ensure their effective enjoyment by protecting the environment and climate system.

With regard to breaches of these obligations, the Court found that such violations constitute “an internationally wrongful act”, and that legal consequences may arise as a result. These consequences could include reparations, guarantees of non-repetition, and cessation of the wrongful act or acts.

While remedies for breaches of state obligations remain limited, the Court has provided the international community with a normative compass that sets clear expectations for states and the regulation of companies operating within their borders. By clarifying the standards of state conduct, the Court has paved the way for strengthening existing mechanisms related to loss and damage and enhancing accountability frameworks. The opinion also offers practical guidance for crafting domestic regulations aligned with states’ international obligations, carrying meaningful consequences for non-state actors. Ultimately, the ruling marks a pivotal step in the normative evolution of climate responsibility, underscoring that climate action is a legal and moral duty integral to the fabric of international law, even if enforcement remains a challenge.

Unlocking legal mechanisms for faster climate action

Emily Ghosh – US Equitable Transitions Program Director

The ICJ has now established that states have legal obligations to protect the climate system from greenhouse gas emissions. Although this advisory opinion lacks direct enforcement power, it creates new leverage points for accelerating climate action.

Global climate action has proceeded too slowly, with current mitigation measures and finance insufficient to achieve global climate goals. While climate finance continues to expand, it remains inadequate, addressing only a fraction of the billions in annual climate damages across lower-income countries. Most funding also flows toward mitigation rather than adaptation, even as climate events intensify, particularly affecting small island developing states. The ICJ ruling provides climate-vulnerable countries with stronger legal arguments in multilateral negotiations, potentially shifting power dynamics and strengthening arguments for increasing developed countries’ financial obligations.

The ICJ opinion clarifies that climate action constitutes a legal obligation rather than political preference. The Court interprets the 1.5°C threshold as the primary temperature goal under the Paris Agreement, requiring nationally determined contributions to reflect the “highest possible ambition” in alignment with this target. In the face of rising fossil fuel production, this provides legal foundation for challenging government support for fossil fuel exploration, production and subsidies.

At the domestic level, the ruling establishes legal foundations for climate litigation worldwide, enabling courts to cite the ICJ’s interpretation of state obligations. This may increase the success rates of domestic climate case and subject companies to greater legal pressure. The question remains whether this legal clarity can overcome the lack of enforcement mechanisms, transforming moral and legal pressure into accelerated action before it is too late.

A step towards environmental justice and protecting environmental human rights defenders

Dayoon Kim – SEI Asia Research Associate

The ICJ advisory opinion confirmed that countries should take measures to protect both substantive rights, such as the right to life and the right to a healthy environment, and procedural rights, such as public participation, public access to information, and climate change education. This represents a step towards safeguarding environmental human rights defenders (EHRDs), including youth and Indigenous defenders, who are determined to challenge the structures of climate vulnerability and protect their communities and the environment via education, networking and mobilization.

In doing so, they face immense risks including extrajudicial killings, in-person and online threats and harassments, and red-tagging. Global Witness reported that at least 2106 EHRDs were killed between 2012 and 2023 while protecting their lands and the environment from harm. In the face of democratic rollback and closing civic space, stronger protection of the right to defend rights is more needed than ever – reaffirmed by another advisory opinion by the Inter-American Court of Human Rights. Despite no explicit mention of environmental defenders as such, the ICJ advisory opinion still holds significant weight in confirming protections for the universal human right to a healthy environment and procedural rights in the face of the climate crisis.

Climate crisis exemplifies the structural injustice of our world: those who contribute the least are the most affected by it, particularly youth and Indigenous Peoples. Pacific Islands Students Fighting Climate Change and World’s Youth for Climate Justice, who spearheaded the steps toward the ICJ advisory opinion, stated that the opinion will greatly assist climate policy frameworks of justice and equity by affirming legal obligations for intergenerational equity and obligations owed to the world’s most climate-vulnerable states. The ICJ advisory opinion thus advances environmental jurisprudence, requiring states to pursue environmental justice immediately.

Why states must also confront inequality and corruption

Albert Salamanca – Asia Senior Research Fellow

While the ICJ advisory opinion emphasizes the obligations of states to address the adverse effects of climate change, these responsibilities must not only reduce greenhouse gas emissions and protect people – although they are critical goals – but also address systemic inequalities. It is crucial to examine the sources of marginalization affecting individuals, groups and communities, as well as states the opinion calls “specially affected” and “particularly vulnerable”.

States must genuinely address the underlying structural and societal factors underpinning vulnerabilities, making it clear why groups and states are exposed to climate hazards, why they are more susceptible to impacts, and why their capacities to adapt are limited. In fulfilling their obligations, states must ensure that core human rights principles guide national development to implement just and effective adaptation.

In addition to the various shocks and stresses caused by climate change, states must also address how corruption reinforces inequalities. One of the fundamental principles of locally led adaptation is providing patient and predictable funding to communities and grassroots organizations, which is crucial to meeting basic needs. Corruption undermines these efforts, straining the already-limited resources of states to strengthen the adaptive capacities of marginalized communities and fostering violence that diminishes the ability of vulnerable groups to adapt to climate impacts.

Without just and effective adaptation, repeated exposure to these shocks and stresses, compounded by structural inequalities and other hazards, can lead to significant losses and damages and make disasters potentially catastrophic for the most vulnerable. As such, it is critical that states work to understand the causes of vulnerability and support marginalized groups while carrying out their obligations under the ICJ advisory opinion.

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