In July 2025, the International Court of Justice (ICJ) in its Advisory Opinion on the Obligations of States in Respect to Climate Change, clarified what climate-impacted communities, youth movements, and courts across the world have been arguing for years: climate action is not a political choice, but a binding legal obligation.

Under international, human rights, and environmental law, states are compelled to act to prevent foreseeable climate and environmental harm. This obligation includes the duty to regulate the conduct of public and private actors, accompanied by effective monitoring and enforcement mechanisms, ensuring that their policies do not undermine the global effort to limit warming. These duties apply across sectors and borders. There is no exemption for trade.

For the European Union, this clarification has immediate consequences. It exposes a profound legal contradiction at the heart of the EU–Mercosur trade agreement: an agreement designed to expand emissions-intensive trade, deforestation, and extractive production, which cannot be reconciled with the EU’s climate obligations under international and EU law.

This is not a matter of political disagreement. Nor left-right political spectrum. It is a matter of legality and upholding the Rule of Law.

The ICJ Advisory Opinion: Climate Obligations Are Binding and Cross-Sectoral

The ICJ Advisory Opinion establishes three decisive principles for EU trade policy:: 

1. Obligation to Prevent Climate Harm: States must prevent significant climate harm, including that caused by greenhouse gas emissions (particularly those caused by fossil fuels). This duty is grounded in customary international law, treaty law, and human rights law.

2. Due Diligence Across Economic Actors: States must regulate activities within their jurisdiction and control, including those carried out by private actors and corporations. As well as monitor and enforce said regulations. Climate harm caused by economic activity is unequivocally legally relevant.

3. Policy Coherence: Climate obligations cannot be postponed by economic or geopolitical interests. States cannot simultaneously commit to limiting warming and adopt policies that foreseeably undermine that objective.

Courts are already operationalising these duties. In the Bonaire Climate Case, a Dutch District Court explicitly cited the ICJ Opinion to hold the State accountable for failing to protect residents from climate harm. International climate obligations are legally binding and enforceable. Not aspirational.

EU Climate Obligations Are Not Optional

The EU is not merely politically committed to climate action, it is legally bound. These obligations apply to all EU action, including trade agreements: 

• Under EU primary law:

  • Article 21 TEU requires EU external action to promote environmental protection, human rights, and sustainable development.

  • Article 191 TFEU embeds the precautionary principle and preventive action as binding norms.

• Under EU secondary law:

  • The European Climate Lawmakes climate neutrality by 2050 and emissions reductions by 2030 legally binding.

  • All EU policies must align with the Paris Agreement.

• Under international law:

  • The EU and its Member States are bound by the Paris Agreement, now reinforced by the ICJ’s clarification of States’ obligations to prevent climate harm.

The Role of the CJEU and Written Observations

The European Parliament's referral of the EU-Mercosur Agreement to the CJEU is recent. Written Observations are only now being prepared. This matters, as the ICJ Advisory Opinion, handed down in July 2025, can and should be integrated into the Parliament's Legal Service submission as international legal authority, not political commentary.

Individual MEPs cannot submit observations directly, but they can request that the Parliament's Legal Service incorporate the AO's findings, specifically that facilitating foreseeable climate harm through trade policy is not a question of discretion but one of legal obligations. Courts are already treating it as such: the Bonaire District Court cited it explicitly to hold a State accountable for climate inaction. The CJEU should be given the opportunity to do the same.

Member States may also submit Written Observations to the CJEU. Even where a political party in government voted NO to the referral, this new “neutral” legal avenue remains open. The question is whether they will use it!

In parallel, Parliamentary Questions to the Commission and Council can establish on the record whether the AO has been considered at all and if not, why not. Likewise, a request for their Legal Services to include this in the Written Observations could be the difference between the CJEU ruling on yesterday's legal landscape and today's.

The planet will not wait. Neither should the law.

Mercosur: A Foreseeable Climate Harm Machine

The EU–Mercosur Agreement is structured to expand precisely those sectors most responsible for climate destruction:

• Industrial agriculture (beef, soy, animal feed)

• Land-use change and deforestation

• Fossil-fuel-dependent transport and logistics

These impacts are documented, foreseeable, and acknowledged even by the Commission’s own sustainability assessments. By locking in trade flows linked to deforestation and emissions, the Agreement externalises climate harm to Mercosur countries while allowing the EU to claim territorial emissions reductions. This is exactly the kind of conduct the ICJ Advisory Opinion warns against: outsourcing emissions does not absolve responsibility.

Soft Sustainability vs Hard Trade Law

Legally, the imbalance in the agreement is stark.

The Mercosur agreement creates:

• binding, enforceable obligations for market access and investor protection,

• while relegating climate, labour, and human rights commitments to a non-sanctionable Trade and Sustainable Development chapter.

This asymmetry violates the principle of due diligence highlighted by the ICJ. When States know that an agreement will facilitate climate harm, voluntary cooperation mechanisms are legally insufficient.

Binding economic rights paired with non-binding climate safeguards amount to structural negligence.

A Question of Legal Coherence, Not Protectionism

The European Parliament’s rejection of the EU–Mercosur agreement reflects an emerging legal reality: trade agreements incompatible with climate obligations are no longer defensible under EU law.

This is not protectionism, nor isolationism. It is about legal coherence. 

The ICJ Advisory Opinion removes the last remaining excuse that climate commitments can be balanced away against economic interests. They cannot.

Conclusion: No Trade Deal Above the Law

The EU cannot claim climate leadership while pursuing trade agreements that knowingly accelerate climate harm. The ICJ has made clear that States will be judged not by their rhetoric, but by the real-world consequences of their policies.

If the EU–Mercosur agreement cannot be aligned with the EU’s climate obligations through binding, enforceable, and Paris-compatible provisions, then the only legally sound option is to not ratify it.

Climate justice is not a slogan. It is the law.

About the author: Alexandere Chao Viso is a member of WYCJ’s Europe Front and holds a MA in EU International Relations and Diplomacy Studies at the College of Europe, with the European Neighbourhood Policy Scholarship. Alexandre is an advocate for human rights and protection at the national, regional and international level. You can reach out to Alexandre at alexandre.chaoviso@coleurope.eu.