Is All Law Climate Law?

On 23 July 2025, the International Court of Justice (ICJ) delivered its Advisory Opinion on the Obligations of States in Respect of Climate Change (Climate Advisory Opinion), confirming that numerous international law obligations govern State conduct adversely affecting the climate system – extending far beyond the UN Framework Convention on Climate Change (UNFCCC), Kyoto Protocol, and Paris Agreement. The Court rejected the lex specialis argument made by some states and confirmed that, in addition to the specific climate change treaties, diverse fields including human rights law, the law of the sea and other environmental treaties are applicable (paras [162]-[171]). The Court also confirmed important customary international law duties, such as a duty to prevent significant harm to the environment (paras [132]-[139]) and the duty to cooperate (paras [140]-[142]), and articulated a stringent due diligence standard (paras [237]-[249]). In this manner, the Climate Advisory Opinion expands our understanding of climate law both horizontally – by reaching into numerous other areas of law – as well as vertically – by influencing our understanding of how states must regulate activities that impact the climate system.

As climate change is a pressing and complex threat facing the planet, we ask whether a focus on ‘climate harm’ provides a productive way to bring together traditionally siloed areas of law and generate comprehensive responses to the current crisis. Our reflections and tentative conclusion – drawing on our respective areas of expertise of water, peace and security, corporate sustainability, and constitutional law – are below. While the expansion of climate law is not limited to these areas, they serve as examples of the vertical and horizontal expansion currently observed in climate law and articulated by the ICJ, and our observations join those of other commentators in arguing that climate change is transforming all areas of law.

Water law

The expanding scope of climate law foreshadowed by the ICJ is inspiring aligned litigation efforts in other areas of environmental concern and natural resource management such as water law. While climate law and international and domestic water law have traditionally developed and been implemented in different domains, water and climate are increasingly intersecting in domestic and transnational climate litigation.

This overlap makes sense on a practical level. Rising temperatures present risks to water supplies and water-related ecosystems, climate change is likely to cause more severe floods and droughts, and bodies of water are tangible signifiers of climate harm. However, while efforts to include water issues more explicitly in international climate discussions have increased, water remains sidelined in formal climate decision-making.

A recent rise in legal actions that deal with both water and climate change takes many forms, including rights-based approaches like legal rights for bodies of water that also reference climate impacts or climate justice, or actions to protect groundwater from degradation that reference climate change. A common area of overlap is legal challenges to fossil fuel projects based on water impacts. For example, while Australia’s environmental impact assessment laws have been critiqued for lack of integration of climate change, the ‘water trigger’, which triggers assessment of surface and groundwater impacts from coal and unconventional gas projects, has featured in judicial challenge. Employing water to directly or indirectly challenge mining projects is also a feature of the overlap between water and climate litigation in other jurisdictions. Many of these cases might genuinely be driven out of concern for bodies of water, but they indirectly impact climate mitigation and adaptation outcomes.

While the bringing together of water and climate law might be a productive avenue for furthering climate aims, there remain questions of motivation and aspiration – does focusing alternately on ‘water’ or ‘climate’ get litigants or advocates what they want? There is also potential for legal actions related to water to clash with the climate-related legislative agendas of states – for example, some countries include hydroelectricity projects as part of their climate transitions, and many renewables projects have water impacts.

International peace and security law

International peace and security law, to the extent that it addresses harm, focuses on humans, state, and property. While certain conduct that causes environmental damage is prohibited by some disciplines within the field, many of the broader questions of climate harm remain outside their current scope.

Nevertheless, there is a growing recognition that wars and climate change are linked. Climate change is understood as a threat multiplier which intensifies insecurity, instability and social tensions. Conversely, armed conflict harms (para 2) the environment and can have a detrimental impact on the climate.

International humanitarian law (IHL) recognises this, in part, and seeks to prevent harm by characterising the natural environment as ‘civilian’ (paras 18-21). It also specifically prohibits means and methods of warfare that ‘cause widespread, long-term and severe damage to the natural environment.’ More generally, however, many ‘normal’ military activities during contemporary conflicts have high carbon footprints and thus negatively affect the climate, such as aerial warfare, energy-intensive artificial intelligence in modern weaponry, or extensive use of concrete to build protective structures. Yet these issues are beyond the purview of the current IHL framework.

International criminal law is traditionally anthropocentric in nature but eco-centric considerations are increasingly taken seriously by the field. Most prominently, a proposal to include a separate crime of ‘ecocide’ in the Rome Statute, the International Criminal Court’s (ICC) founding treaty, is currently under discussion. Beyond this, the ICC’s current legal framework already offers options to address certain harm to the environment, such as article 8(2)(b)(iv), which considers environmental destruction a war crime if it causes disproportionate harm. A recent Policy Paper by the ICC Office of the Prosecutor furthermore outlines how environmental dimensions of Rome Statute crimes may be prosecuted and marks the Office’s commitment to do so. While climate harm unconnected to the Statute remains outside the Court’s jurisdiction, the Policy Paper shows a willingness to address environmental damage more holistically, in times of war and peace.

These growing intersections between international climate law and international law concerned with peace and security, which has often been considered one of the most ‘remote’ from environmental concerns, illustrate the horizontal effect of climate law expansion.

Nature and corporate accountability

The Climate Advisory Opinion also brings climate law into a closer relationship with laws regulating businesses and corporate conduct. Climate change can be understood as a crisis of harm – to people, communities, and critically, to nature itself. Approaching climate change through this lens exposes limitations in corporate accountability frameworks, which continue to conceptualise climate change and biodiversity loss primarily as sources of financial risk, rather than as forms of ecological damage for which responsibility should be allocated. While the ICJ partially addressed the need for states to regulate the conduct of private actors like corporations within their jurisdiction ([e.g. para [427]], the question of whether ‘all law is climate law’ becomes a question about how responsibility for climate harms is distributed, diluted, or deferred across legal domains.

One manifestation of this problem lies in the historical fragmentation between specialist areas of international law. Although climate change and biodiversity loss are mutually reinforcing, they have developed through distinct international regimes and are often implemented domestically through separate regulatory pathways. This fragmentation enables mitigation strategies that prioritise carbon outcomes while sidelining ecological integrity.

Market-based mechanisms illustrate this dynamic. Internationally, REDD+ was promoted as a means of reducing emissions while delivering biodiversity co-benefits. In practice, persistent shortcomings mean that emissions reductions may be achieved while underlying ecological harm remains unaddressed. Similar tensions are evident in the Australian Carbon Credit Unit Scheme, where land-based abatement plays a central role in meeting net-zero targets despite ongoing challenges in alignment with biodiversity objectives. In this context, corporate climate compliance may involve displacement of harm onto ecosystems through credits generated under conditions of ecological uncertainty.

These dynamics are reinforced by the dominant framing of corporate obligations around financial materiality. While climate risk governance, including through the Taskforce on Climate-related Financial Disclosures, has focused on risks to firms, emerging nature-related frameworks – particularly the Taskforce on Nature-related Financial Disclosures – mark a conceptual shift by recognising systemic risk arising from corporate impacts on nature. This reflects the reality that biodiversity loss can undermine shared ecological foundations long before harm crystallises as company-level financial risk, exposing the limits of accountability frameworks that prioritise risks to corporations over harms they cause.

Constitutional law

The Climate Advisory Opinion also considers the ‘vertical’ effects of its findings in respect of shaping domestic regulation, an effect that will be mediated through constitutional and administrative law in implementing states.

Constitutions offer diverse mechanisms to address climate harm. Rights-based approaches provide one avenue – many countries have constitutionally protected right to a healthy environment. Structural reforms to improve accountability, democratic participation, and environmental decision-making provide another. Yet climate constitutionalism faces challenges due to state capacity limitations, under-specificity of provisions, conflicts with constitutional values, and the mismatch between constitutional time horizons and climate urgency.

The Eighth Melbourne Forum Report illuminated these points by drawing on 16 Asia-Pacific case studies, highlighting innovative solutions from the region – such as Tuvalu’s constitutional provisions anticipating territorial loss to rising seas while claiming continuing sovereignty – whilst demonstrating how climate impacts pose security, equality, governance capacity, and mass displacement challenges, placing pressure on constitutions.

Turning to climate litigation, it has been suggested that the Climate Advisory Opinion leans into an increasingly ‘administrative’ law turn in international law. One can detect a similar turn in the argumentation before and reasoning of the Court.

• First, the Court recognized the right to a clean, healthy, sustainable environment as inherent in other rights through necessary implication from text, structure, and purpose (paras [389]-[393]) – an implication from practical necessity.
• Second, the freedom of discretionary climate action under the Paris Agreement is limited in its operation by due diligence obligations, with no lex specialis displacement (paras [166]-[170], [239]-[245], [270]), reflective of approaches to operational inconsistencies between laws involving discretionary powers – that is, where the inconsistency arises only if and when there is a particular exercise of discretionary power, rather than on the face of the laws or by any discernible intention to displace other applicable laws.
• Third, the Court acknowledged separation of powers concerns and justiciability boundaries, while still addressing threshold issues like attribution and causation (paras [45], [427]-[430], [437]-[438]) – overcoming the ‘climate overloading’ argumentation tactic which has caused difficulties for climate litigation in some domestic courts.

Finally, the campaign for the case – conceived by Pacific Island students, driven by the youth and civil society, and championed by Vanuatu at the diplomatic level – produced the highest participation and most representation in ICJ history. The process involved innovative lawyering, with civil society effectively using advisory procedures in a court process designed for States (and without objection). That is rather remarkable – and deserves attention from constitutional, climate, and international law scholars alike.

Conclusion

Diverse areas of law are increasingly engaging with climate change and climate harm. Yet, many continue to operate in silos, lacking coherent frameworks for integrating what might be called ‘climate law’. Interaction is ultimately unavoidable: as the ICJ has noted in its Climate Advisory Opinion, the causes and consequences of climate change are multi-scalar, multi-actor, and intergenerational and has expanded our understanding of climate law. This complexity warrants serious consideration of the extent to which all areas of law should at least be speaking to climate law.

Eco friendly law, politics and eco balance concept. 3d rendering of scale icon on fresh spring meadow with blue sky in background.

Roanna McClelland

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Roanna McClellandis a Research Fellow at the Laureate Centre for Global Corporate Climate Accountability at Melbourne Law School. Roanna's research incorporates interdisciplinary and empirical research methods, spans the private and public sectors, and explores intersections between areas of law including climate, water, environment, human rights, social movements, and corporate accountability. Roanna has extensive experience across academia, policy and media, including as adviser to the Premier of South Australia, and to former Prime Minister Julia Gillard.

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