Decision Commented On: Obligations of States in Respect of Climate Change, Advisory Opinion of the International Court of Justice (2025)
PDF Version: Canada’s Internationally Wrongful Climate Acts
Over the past decade, litigants—mainly young people—have petitioned domestic courts worldwide to assess if governments are doing enough to combat climate change. Courts in Europe, Africa, Asia, and South America mostly responded positively, issuing directives for more ambitious climate action. Although similar cases have been brought before Canadian courts, no case has succeeded on its merits in compelling federal or provincial governments to raise the level of their climate commitments. This situation might soon change, especially with the recent landmark advisory opinion from the International Court of Justice (ICJ).
The ICJ was established after the Second World War as the primary judicial branch of the United Nations (UN). Countries worldwide granted the court the authority to resolve legal conflicts and provide advisory opinions on international law issues. International law, as interpreted by the ICJ, primarily consists of treaties and binding norms and practices that are widely accepted and recognized as law (customary international law). While all parties who have ratified a treaty must abide by it, customary international law applies to all nations. For instance, torture is internationally acknowledged as wrongful regardless of whether a country has signed the treaty against torture, just as is the case with the international rule against pollution that causes harm in other countries.
The ICJ’s recent advisory opinion on the obligations of States regarding climate change addressed both treaties and customary international law. While advisory opinions are not legally binding in themselves, they serve as authoritative interpretations of treaties and customary law. Advisory opinions should guide how governments and domestic courts interpret and implement international law. The recent opinion, therefore, provides authoritative guidance on Canada’s climate mitigation and adaptation commitments, its duty to regulate corporate activities, and its obligation to cooperate with other nations to support vulnerable countries under international climate agreements and customary law. Failure to meet these obligations could make Canada responsible for internationally wrongful acts. Additionally, Canada’s failure to fulfill its climate obligations may be extremely costly, as the country could be legally liable for paying reparations to nations adversely affected by climate change.
The Duty to Mitigate
In 2015, countries from around the world, including Canada, gathered in Paris, France, and committed to collectively keeping the global temperature increase to less than 2 °C above pre-industrial levels, and striving to limit it to 1.5 °C. In the years following the Paris Agreement, it has become clearer that while a 1.5°C rise will lead to increased flooding, drought, heatwaves, and some countries and communities going underwater, a 2°C rise would be significantly worse. A consensus for a 1.5°C target has therefore emerged among countries committed to the Paris Agreement. In its advisory opinion, the ICJ provided legal backing to the 1.5°C target as the collective goal for nations (para 224). According to the court, this target must guide the commitments and ambitions of states in reducing their greenhouse gas emissions (para 242).
Canada’s obligation to mitigate includes the legal duty to submit a 1.5 °C-compliant nationally determined contribution (NDC) containing its climate mitigation goals every five years, as well as an obligation to make every effort to achieve those climate goals (Paris Agreement, article 4(2)). Every country, developed or developing, is obliged to submit an NDC under the Paris Agreement. The ICJ noted that countries do not have untrammelled discretion to decide and communicate emission reduction (climate mitigation) targets that are progressive and represent their “highest possible ambition” (paras 245 – 246). The court found that countries’ discretion in determining their NDCs is limited and provided basic requirements that NDCs must meet. Canada’s NDC must become more ambitious over time, making an adequate contribution to staying within the 1.5°C target, and be presented in a way that promotes environmental integrity, transparency, accuracy, completeness, comparability, consistency, and the avoidance of dubious accounting (paras 241 – 244).
While every country must make efforts to submit ambitious NDCs, the NDCs of developed countries like Canada, considering their historical emissions and current financial and technological capabilities, will be subject to a rigorous application of the requirements set out in the Paris Agreement and affirmed by the ICJ (para 247). Canada’s current pledge to cut its emissions by 45-50% by 2035, compared to its 2005 levels, is unlikely to meet the ICJ’s standards. This is especially true, as comparable jurisdictions like the United Kingdom (81% by 2035, compared to 1990) and Norway (70-75% by 2035, compared to 1990) have committed to more ambitious emission reduction targets. Norway and the United Kingdom, like Canada, are major oil and gas producers. Both countries are the top two oil and gas producers in Western Europe.
However, even if Canada’s 45-50% emission reduction commitment were accepted, a significant gap remains between the country’s pledge and its policy plans to achieve it. The recent NDC submitted in 2025 is Canada’s third NDC. The country, however, failed to meet the targets committed to under NDCs submitted in 2015 and 2020. Ambitious NDCs alone do not fulfill the legal climate mitigation obligations of states. Each country must adopt and implement domestic measures to meet its commitments. While countries only have an obligation of conduct—not result—with respect to the targets they have committed to, they must exercise due diligence in fulfilling this obligation (para 251). In other words, while there is no obligation to achieve these targets, they must deploy all appropriate measures and best practices to reach their targets (paras 252 – 253).
Climate mitigation measures will differ across countries. The Paris Agreement allows NDCs and related instruments to reflect each nation’s circumstances. However, every country should have legislative, administrative, and enforcement mechanisms that effectively enable it to meet its NDCs. Canada’s main climate legislative tools, the Net-Zero Emissions Accountability Act (NZEAA) and the Greenhouse Gas Pollution Pricing Act (GGPPA), arguably do not meet these high standards. The NZEAA is not action-forcing, and the GGPPA is weakening over time. Canada must now review its climate laws and measures to ensure they align with the requirements affirmed by the ICJ based on its interpretation of treaties Canada has agreed to and international custom. Just as Canada’s NDCs must be ambitious and progressive, implementation measures should also be equally forward-looking and bold.
The One Canadian Economy Act also risks breaching Canada’s climate mitigation commitments if it promotes the development of infrastructure for increased exploration, production, subsidization, and use of fossil fuels (para 427). As clarified by the court, emitting GHGs is not inherently an internationally wrongful act. However, neglecting to take climate-protective measures in relation to fossil fuel activities might be indicative of Canada’s failure to fulfill its climate obligations. Emissions from fossil fuels are the main driver of climate change. Canada cannot meet its climate commitments without addressing this reality in a meaningful way.
The Duty to Adapt
Climate change is no longer a distant threat; it is a current reality. A sudden halt to global emissions today would bring significant benefits for future generations. Still, it would not protect the current generation from the already locked-in negative impacts of climate change. For example, Tuvalu is already implementing plans to relocate its population to Australia as the island gradually disappears into the Pacific. Countries in Sub-Saharan Africa are currently experiencing some of the most severe effects of climate change. Here at home, permafrost in Canada’s North continues to melt quickly, putting Indigenous communities and residents in danger.
The certainty of adverse impacts from climate change makes climate adaptation a crucial part of international climate law. Climate adaptation measures help individuals and communities prepare for and adjust to the current and expected effects of climate change. Although it receives less attention than climate mitigation in international climate agreements, the ICJ reaffirmed important climate adaptation obligations that Canada and other nations must fulfill (para 255).
Canada must take appropriate measures to strengthen the resilience of Canadians and Canadian infrastructure, reduce their vulnerability to climate change, and improve their ability to adapt (para 256). The ICJ emphasized that the country should make its best efforts towards these goals in line with current scientific knowledge (para 258). Although there is no mandatory list of actions, it can be argued that the indicative list in the Paris Agreement—such as having national adaptation plans and assessing climate change impacts and vulnerabilities to develop actions that consider vulnerable people, places, and ecosystems—is a minimum requirement.
Canada’s adaptation strategy has been criticized as inadequate. There is little meaningful integration of climate adaptation into its regulatory impact assessment framework. The country also falls short on other measures highlighted by the court, including early warning systems, ecosystem restoration, and climate-resilient infrastructure. The public’s knowledge and awareness about place-specific climate impacts remain limited. Additionally, there is no coordinated system to proactively and actively educate and inform Canadians about the vulnerabilities of communities and places to climate change.
There is no Canada-wide map and database on climate vulnerability comparable to the US National Oceanic and Atmospheric Administration’s Climate Mapping for Resilience and Adaptation (CMRA). The closest equivalent is a Government of Canada website that hosts a Quebec climate database with a disclaimer stating that the “resources are not under the control of the Government of Canada.” The Climate Atlas by the Prairie Climate Center at the University of Manitoba is a very useful tool, albeit complex. However, public awareness of this platform remains limited. Provinces, especially in the Atlantic region, and several Indigenous groups have developed adaptation plans and strategies. Nonetheless, there is no meaningful coordination among provincial and federal adaptation plans and strategies. The legal framework for climate adaptation at both the federal and provincial levels is currently highly fragmented and mostly only implicitly relevant to climate resilience and adaptation.
The Duty to Regulate
Failing to properly regulate the actions of companies that contribute to climate change could make Canada liable for an international wrongful act. Traditionally, international law has focused on the obligations and actions of states. As a result, companies are generally considered to have no obligations under international law. However, the trend in Canada and other countries has shifted. The Supreme Court of Canada, for instance, has decided that a company could be held liable for human rights abuses under customary international law. In other countries, courts have used international climate agreements to establish the climate responsibilities of corporations.
Although the ICJ stopped short of ruling that corporate entities have direct climate obligations under international law, it stated that failing to regulate their activities could indicate a state’s failure to fulfill its climate commitments (para 428). It may also suggest that a State is not complying with its duty under customary international law to prevent significant environmental harm (para 282). Consequently, Canada must establish regulatory mechanisms that bind both public and private entities under its control to achieve deep, rapid, and sustained reductions in emissions and to minimize climate-related risks. Additionally, systems for monitoring and enforcement are essential. Although Canada has laws and policies at the federal, provincial, and municipal levels regulating corporate emissions, it lacks comprehensive climate change due diligence tools present in other countries.
Impact assessment is particularly important in this context. According to the ICJ, States should provide and carry out impact assessments regarding how projects within their jurisdiction or control contribute to GHG emissions, using the best available science (para 298). Impact assessment is an indicator that a country is making its best efforts to meet its climate obligations under customary international law. Importantly, the Supreme Court of Canada has been clear that customary international law forms part of Canada’s common law.
All of this has direct implications for the upcoming – second – Reference re: Impact Assessment Act. In the first Reference re Impact Assessment Act, 2023 SCC 23 (CanLII) (First Reference re: IAA), a majority of the Supreme Court of Canada held that the federal IAA was beyond Parliament’s legislative authority because the Act was insufficiently focused on areas of federal jurisdiction. Canada subsequently amended the Act, but Alberta was unsatisfied with those changes and referred the amended Act to another reference before the Alberta Court of Appeal.
With respect to transboundary environmental harm specifically, the Supreme Court in the First Reference re: IAA constrained prior precedents to establishing federal jurisdiction over marine pollution, transboundary river pollution, and national standards of carbon pricing – not transboundary air pollution per se (at paras 182 – 189). The ICJ highlighted impact assessment as a due diligence requirement for fulfilling Canada’s duty to prevent significant harm to the climate system (paras 295 – 298). While an opinion of the ICJ does not alter the constitutionally established distribution of power in Canada, it certainly seems clearer now that Canada has an international obligation to assess projects’ GHG emissions that at least one level of government will have to meet. It will be interesting to see whether such arguments come up in the second Reference.
The Duty to Cooperate
Climate change cannot be dealt with by the efforts of any single country, no matter how ambitious. Global emissions collectively contribute to climate change, and their impacts do not respect borders. The ICJ describes the climate system as a shared resource belonging to all states (para 302). It is a matter of common concern for humankind that requires international cooperation. Climate agreements, including the Paris Agreement, acknowledge the vital importance of countries working together to fight climate change.
The need for cooperation becomes even more essential, especially since the emissions-intensive industrialization of countries like Canada has significantly contributed to climate change, with its worst impacts felt disproportionately by countries with the least emissions. That is why supporting emission reduction and adaptation efforts in developing nations is a vital part of every international climate agreement. However, the obligation to cooperate extends beyond international agreements, as it is also a customary international law norm. Even if a country is not a signatory to an international climate treaty, it still bears a duty to make good faith efforts to collaborate with other nations to combat climate change (para 304).
Good faith and understanding are vital to the duty to cooperate. They recognize the interdependence of States and the importance of each nation genuinely contributing its fair share. Fair burden sharing and responsibility are essential. According to the ICJ, the duty to cooperate and prevent significant environmental harm is a legal standard used to evaluate whether international agreements and their implementation meet their objectives and whether additional collective actions are needed (para 307). Canada has an obligation, considering its historical emissions, current capabilities, and circumstances, to commit to emission targets that fairly reflect its burden. It has been estimated that Canada’s fair contribution to the global temperature goal should be a 140% reduction by 2030, including at least a 60% domestic emission reduction and the rest through support for developing countries.
Although countries can choose their mode of cooperation, refusing to cooperate is not an option. The court also acknowledged that financial assistance, technology transfer, and capacity building are primary forms of collaboration (para 306). As a developed nation, Canada has a duty to provide and support financial aid, technology transfer, and capacity development to developing countries in line with the 1.5°C target. Canada is behind in delivering international support to developing countries, with its climate finance contributions currently considered highly insufficient.
A Powerful Jab but not a Knock-out
As the impacts of climate change grow more severe in Canada through wildfires, heatwaves, and flooding, causing loss of life, livelihoods, and ecosystems, levels of government have engaged in unnecessary jurisdictional disputes and consistently weaken already insufficient climate policies and laws. The ICJ’s opinion is not a cure-all, but it is an important step forward.
The court clarified the previously vaguely defined obligations that governments have used to justify inaction on climate change. Canada’s climate obligations extend beyond the Paris Agreement, encompassing customary international law and various international treaties it has ratified, notably the 1992 United Nations Framework Convention on Climate Change and the 1982 United Nations Convention on the Law of the Sea (UNCLOS). An earlier opinion of the International Tribunal for the Law of the Sea addressed States’ climate obligations under UNCLOS. The common argument that governments cannot be legally responsible for climate change because climate harm cannot be directly linked to their actions has been weakened by the ICJ. The court clarified that attribution — the responsibility for failing to meet climate obligations — differs from causation, which pertains to liability for the harm caused by climate change (para 422).
Attribution alone suffices to establish responsibility for an international wrongful act (para 428). Notably, the court has rejected the idea that States cannot be held liable for climate-related harm requiring reparations, even though proving causation remains challenging (paras 433 – 438). Canadian courts will also need to interpret the Canadian Charter of Rights and Freedoms in light of the ICJ’s opinion that climate change can impact rights such as life, health, and privacy under international human rights treaties, to which Canada is a signatory (paras 376 – 393). Additionally, by recognizing climate obligations under customary international law (para 409), all levels of government in Canada are required to make their best efforts to combat climate change within their jurisdictions.
To the realist, international law is the law of the powerful by the powerful for the powerful. Powerful countries ignore it freely, while weaker nations can be compelled into obedience. In an ideal world, every country should consider the opinion of the ICJ to review, set higher ambitions, and genuinely implement its climate laws and policies. Every nation, whether or not it is a party to an international climate agreement, should pass laws, adopt policies, and take actions to protect a deteriorating climate. This is because the duty to safeguard the climate is rooted not only in treaties but also in the core practices and norms that are believed to bind every country. These norms include a responsibility to ensure that activities in one country do not harm another and to cooperate in protecting global spaces over which no single State holds exclusive jurisdiction.
The world is far from ideal, and as the ICJ acknowledged, there are limits to international law (para 456). The effectiveness of the ICJ’s opinion depends on human will and wisdom, as the court pointed out, to make tough choices for protecting our planet and future generations. Hopefully, Canada and its people will see this decision, made by 15 individuals from around the world, as a call to unite our collective resolve and wisdom in halting our rapid slide into disaster.
Adebayo Majekolagbe, PhD, Assistant Professor at the Faculty of Law, University of Alberta. I sincerely appreciate the comments, feedback and inputs from Martin Olszynski, Sara Seck, and an anonymous reviewer. Any errors in this post are, however, my own.
This post may be cited as: Adebayo Majekolagbe, “Canada’s Internationally Wrongful Climate Acts” (15 August 2025), online: ABlawg, http://ablawg.ca/wp-content/uploads/2025/08/ Blog_AM_CanadaICJClimate.pdf
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