Defending Rights in a Changing Climate: A Practitioner’s Guide to the Advisory Opinions of the Inter-American Court of Human Rights and the International Court of Justice

The ICJ’s Opinion determined that the 1.5°C temperature target is legally binding under the Paris Agreement and nations can be held legally accountable for their due diligence obligations to limit greenhouse-gas emissions. Similarly, in the IACtHR’s Opinion, the Court recognizes the State obligation to respect and guarantee the right to defend human rights, a special State duty of protection towards environmental rights defenders, and the right to a healthy climate and the rights of nature. The discussion unpacked the various frameworks outlined by the two Opinions, analyzed the potential responses of States to them, and explained their implications for practitioners. 

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Here are some key points discussed:

Inter-American Court of Human Rights (IACtHR) Advisory Opinion No. 32

• Date published: July 3, 2025
• Requested by: Chile and Colombia (January 2023)
• Focus: State obligations in responding to climate change under Inter-American human rights law
• Participation: over 600 actors submitted written observations; two hearings held

International Court of Justice (ICJ) Advisory Opinion No. 36

• Date published: July 23, 2025
• Requested by: United Nations General Assembly (March 2023)
• Focus: State obligations under international law and legal consequences of contributing to climate harm
• Participation: over 150 written submissions; two-week public hearing with participation by 96 states and 11 international organizations

1. Shared Legal Conclusions

• Both courts affirm that a healthy environment is necessary for the enjoyment of human rights, including the rights to life, health, water, and cultural identity.
• States have legal duties to act, grounded in both treaty law (e.g., Paris Agreement) and customary international law.
• Both courts articulate an obligation of due diligence by States to prevent climate harm.
• States must take measures to regulate business activities that contribute to climate change.

2. Key Findings from Each Opinion

IACtHR Opinion

• States must exercise due diligence to take all necessary measures to reduce risks arising from degradation of the global climate system and resulting harms.
• States must regulate private actors in a manner consistent with the United Nations Guiding Principles on Business and Human Rights.
• Nature and its components are subjects with legal rights.
• The state has the obligation to incorporate scientific and traditional knowledge, particularly from Indigenous and local communities, when planning mitigation and adaptation measures.
• The state has the duty to protect vulnerable populations, including children, Indigenous peoples, Afro-descendant communities, and people in poverty.
• Calls for climate-related disclosures by states and companies; affirms right to access to justice for environmental harms.
• Supports legal actions where companies violate these standards.
• The prohibition of actions causing irreversible damage to the global ecosystem on which life depends is a jus cogens norm.

ICJ Opinion

• The court interprets the Paris Agreement as requiring a 1.5°C goal (not 2°C); holds states to “stringent” but “reasonable” due diligence standards.
• Due diligence is customary international law
• The Opinion does not explicitly recognize a customary law human right to a healthy environment, but acknowledges interlinkages between environmental harm and rights to life, health, etc.
• Obligations are erga omnes: States owe duties to the global community.
• The Opinion does not impose direct obligations to cease fossil fuel production, but recognizes relevance for assessing state compliance.
• General international law remedies remain applicable — cessation, guarantees of non-repetition, reparations including compensation, etc.

3. Implications for Business

Legal Risk and Litigation

• Companies may be involved in litigation:
  
  • As defendants for contributing to climate harms.
  • As plaintiffs defending sustainable operations using advisory opinions as legal shields (e.g., Brazilian wind energy case).
• Use of advisory opinions as legal grounds:
  
  • Already cited in litigation in Brazil.
  • Likely to be referenced in domestic courts, particularly in jurisdictions that integrate international law directly (e.g., Brazil’s 2002 decree recognizing IACtHR advisory opinions as binding).

Corporate Due Diligence Standards

• Integration of climate considerations into human rights due diligence is now an expected standard in Latin America (IACtHR).
• Disclosure obligations: Companies may need to report on climate risks and impacts.
• The state has the duty to consult Indigenous and local communities in impact assessments.
• Precautionary measures: Duty to act where scientific certainty is lacking but risks are high.

Regulatory Influence

• EU Corporate Sustainability Due Diligence Directive (CSDDD):
  
  • ICJ opinion may pressure regulators to strengthen Article 22 on climate transition plans.
  • Raises questions about whether scaling back corporate requirements would conflict with emerging international norms.

4. Limits and Caveats

• Advisory opinions are non-binding:
  
  • Do not compel state or corporate behavior on their own.
  • Influence depends on how national courts and regulators choose to interpret and apply them.
  • ICJ and IACtHR have long records of noncompliance by states.
  • Legislative responses may be delayed or diluted (e.g., U.S. withdrawal from Paris; EU compromise on CSDDD).
• Implementation varies by jurisdiction:
  
  • Monist systems (e.g., Brazil) may directly incorporate advisory opinions into judicial reasoning.
  • Dualist systems (e.g., U.S.) require domestic legislation to translate international norms into enforceable standards.

5. Strategic Takeaways for Business Lawyers

• Conduct jurisdiction-specific analysis: Evaluate whether and how advisory opinions may influence courts and regulators in each market.
• Prepare for expanded litigation risk: Advisory opinions are likely to be used to support climate-related claims against both states and companies.
• Monitor regulatory developments: International opinions may spur new national or regional regulations, especially in Europe and Latin America.
• Reassess corporate due diligence frameworks: Integrate climate considerations into human rights assessments and stakeholder engagement.
• Avoid overconfidence: Even where enforcement is uncertain, reputational and operational risks are rising.

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