The ICJ Advisory Opinion Comes to Life in Canadian Climate Litigation: Lho'Imggin v. Canada

The International Court of Justice (ICJ) Advisory Opinion on climate obligations is no longer just a theoretical statement of international law. In one of the first concrete applications, the Canadian Federal Court engaged with the Opinion last week in Lho'Imggin v. Canada, a case brought by two Wet’suwet’en hereditary chiefs challenging Ottawa’s climate policies. The Court’s decision demonstrates how international legal principles are beginning to shape domestic climate litigation, even in a system where international treaties are not directly enforceable.

While the Court struck the latest amended claim, it left the door open for the plaintiffs to revise and narrow their constitutional challenge to refer to customary international law elements in the ICJ advisory opinion, keeping alive a potentially landmark climate litigation in Canada.

Persuasive Authority of the ICJ Opinion

The Court emphasised that, although the ICJ Opinion is not binding on states, it identifies key principles that influence state conduct. It underscores that nations have a duty to protect the climate system, rooted in customary international law and human rights obligations. The Opinion’s message is clear: climate change poses existential risks, and states must act immediately to mitigate its effects.

For Canadian courts, this means international law can inform domestic interpretation. Even if treaties like the Paris Agreement or UNDRIP do not create enforceable rights domestically, they set a standard against which Canadian statutes and policies can be assessed.

Dualist Limits: What Canadian Courts Can and Cannot Enforce

Canada follows a dualist approach, meaning international agreements are not directly enforceable in domestic courts unless incorporated through legislation. The Court clarified that direct enforcement of international obligations is not possible, but domestic statutes implementing these obligations—like the Greenhouse Gas Pollution Pricing Act (GGPPA) or the Net-Zero Emissions Accountability Act (CNZEAA)—can be challenged.

In practice, this means the plaintiffs cannot sue Canada directly for failing to meet its Paris Agreement commitments. Instead, they must target specific domestic laws and policies that they allege fail to uphold those international commitments.

Customary International Law as a Path Forward

The Court also highlighted customary international law as a potential basis for novel claims. If plaintiffs can show widespread state practice and a sense of legal obligation (opinio juris) on climate protection, Canadian courts may recognise a common law cause of action. Importantly, the Court followed the Federal Court of Appeal’s guidance that judges should allow “novel but arguable claims” to proceed to trial, encouraging the evolution of law in response to climate change.

International Law Guides Constitutional Interpretation

The case demonstrates how international principles can shape domestic constitutional rights, particularly under Section 7 of the Charter, which protects the right to life, liberty, and security of the person. The Court noted that environmental harm, like that alleged by the Wet’suwet’en, can be assessed in light of international law, even if that law cannot create direct enforceable obligations.

Finally, the Court drew a crucial distinction: obligations owed internationally, such as commitments under the Paris Agreement, cannot be adjudicated directly in Canadian courts. These may constitute internationally wrongful acts, but domestic litigation must focus on the enforceable domestic statutes that implement these obligations. Nevertheless, the Court allowed plaintiffs the chance to amend their claims, creating a path to link customary international law, domestic law, and constitutional rights.

What This Means for Climate Litigation in Canada

Lho'Imggin v. Canada is a turning point. It shows how the ICJ Advisory Opinion can influence domestic climate litigation, guiding courts in interpreting statutes and constitutional rights in line with international expectations. By leaving space for novel claims based on customary international law and precise statutory challenges, the Federal Court signals that Canadian courts are ready to engage with international norms when assessing the adequacy of national climate policies.

This case also sets a precedent for future litigation, demonstrating that international legal principles, while not directly enforceable, can play a persuasive role in shaping domestic climate accountability. As the Wet’suwet’en prepare to amend their claim, the case will be closely watched by climate litigators, policymakers, and Indigenous groups alike, potentially influencing the development of Canadian climate law for years to come.