On 4 February 2025, Mexico formally implemented the USMCA dispute panel's ruling in Mexico – Measures Concerning Genetically Modified Corn (MEX-USA-2023-31-01) by issuing a decree repealing the contested measures. This marks a procedural milestone in resolving the dispute over Mexico’s 2023 restrictions on genetically modified (GM) corn imports. Below, we outline the measures, the panel's findings, and the implications of Mexico’s compliance.

The dispute in brief: the two measures at issue

Mexico's February 2023 Presidential Decree introduced two key provisions targeting genetically modified (GM) corn imports:

1. Article 6.II Measure ("Tortilla ban"): Prohibited the use of GM corn in the production of nixtamalized corn products for human consumption, such as dough and tortillas.
2. Articles 7/8 Measure ("Gradual substitution policy"): Directed government agencies to gradually transition from using GM corn in industrial and animal feed processes to non-GM alternatives, contingent upon food and supply self-sufficiency.

The United States challenged these provisions under USMCA Chapter 9 (Sanitary and Phytosanitary (SPS) Measures) and Chapter 2 (National Treatment and Market Access), arguing that the measures were not based on scientific evidence and created unnecessary barriers to trade.

Panel findings: inconsistencies with USMCA commitments

The panel, in its final report issued on 20 December 2024, found that both measures violated USMCA obligations, primarily because:

• Science-based requirements: Mexico had not conducted proper risk assessments or provided sufficient scientific justification for the measures.
• Premature implementation: The Gradual Substitution Policy predicated regulatory outcomes without completing a risk assessment, which the panel determined was inconsistent with the rules governing sanitary and phytosanitary measures.
• Import restriction: Mexico's measures also constituted an import restriction insofar as no imported genetically-modified corn was allowed into Mexico if destined for the production of nixtamalized products such as tortilla.

The panel concluded that Mexico must bring its measures into conformity with its obligations under the USMCA treaty by ensuring that regulatory measures are based on a scientific assessment and do not disproportionately affect trade.

Mexico’s compliance: formal repeal of the disputed measures

On 4 February 2025, Mexico published the "Acuerdo por el que se deja sin efectos la aplicación de diversas disposiciones sobre maíz genéticamente modificado" in its Diario Oficial de la Federación (accessible here). This Acuerdo declared Articles 6.II, 7, and 8 of the 2023 Presidential Decree ineffective, thereby repealing the measures the panel deemed inconsistent with USMCA provisions.

Reaction from the United States

The Office of the United States Trade Representative (USTR) issued a statement on February 6, 2025, welcoming Mexico's repeal of the measures while noting its intent to continue monitoring the situation. The USTR highlighted:

“The United States will continue to monitor Mexico's agricultural biotechnology measures to ensure science-based implementation consistent with USMCA commitments.”

USTR emphasized the importance of ensuring that agricultural biotechnology policies remain consistent with science-based principles and provide unrestricted market access for U.S. corn exports to Mexico.

Domestic developments in Mexico: Constitutional amendment on GM corn

The repeal of the contested measures resolves the specific dispute at hand and seems to ensure Mexico’s compliance with the USMCA panel’s findings. At the same time, recent developments suggest that the governance of genetically modified organisms (GMOs) in Mexico is evolving further, with potential changes to its domestic regulatory framework.

1. Constitutional amendment on GM Corn: Mexico is reportedly pursuing a constitutional amendment to prohibit the cultivation of GM corn in Mexico. This amendment, grounded in environmental, cultural, and public health considerations, represents a significant development in national policy. Should it be adopted, the amendment would constitute a higher-order legal framework guiding future regulatory measures in Mexico. The constitutional amendment targets domestic cultivation of GM corn, rather than imports or use in nixtamalized foods—issues at the heart of the recent USMCA panel ruling. This distinction:
   

   • Avoids direct conflict with the December 2024 panel report.

   • Preserves Mexico’s sovereign right to regulate domestic agriculture under international law, provided future measures comply with trade obligations (e.g., non-discriminatory seed regulations).

2. Regulatory framework in transition: The proposed constitutional amendment signals ongoing efforts to strengthen Mexico’s domestic governance of GMOs. Any regulatory measures adopted following this constitutional change would need to align with Mexico’s domestic legal framework while adhering to its international commitments, including those under the USMCA.
3. USMCA monitoring and dialogue: In light of these developments, the United States has noted that it will continue to monitor Mexico’s policies under the USMCA framework. Constructive dialogue between the parties will remain important to ensuring mutual understanding and collaborative engagement on agricultural biotechnology governance.

Legislative process and next steps

1. Senate vote: The amendment requires a two-thirds Senate majority (84 votes) for approval. The ruling Morena party holds 78 seats but will need support from opposition lawmakers.

2. State ratification: If approved, 16 of Mexico's 32 state legislatures must ratify it. Observers estimate this could conclude by mid-2025.

3. Implementation: Post-ratification, Mexico must pass implementing legislation to operationalize the ban (e.g., defining enforcement mechanisms, seed regulations).

Implications of the amendment for trade and compliance

1. Immediate impact: The amendment does not affect current U.S. corn exports ($5.6 billion in 2024), as it exclusively governs cultivation.

2. Future regulations: Implementing laws could face scrutiny under USMCA if they indirectly restrict trade (e.g., limiting GM seed imports for research).

3. USMCA Article 31.19: If future measures trigger disputes, either party may request panel reconvening to assess compliance or retaliation levels.

Conclusion

Mexico's repeal of the measures at issue seems to resolve the specific USMCA dispute in full compliance with the panel’s findings. The concurrent pursuit of a constitutional amendment to prohibit domestic GM corn cultivation represents a sovereign policy choice grounded in environmental, cultural, and food sovereignty objectives. If ratified, this amendment—approved by Mexico's Chamber of Deputies and pending Senate review—would exclusively regulate cultivation, a matter outside the scope of the USMCA panel’s December 2024 ruling, which addressed import and use restrictions.

If ratified, Mexico's constitutional amendment—currently advancing through the Senate and state legislatures—would exclusively govern domestic cultivation, distinct from the USMCA panel's focus on imports and use of GM corn. While the cultivation ban operates in a legal domain distinct from trade-related obligations, stakeholders may monitor its implementation to assess alignment with Mexico's international commitments. The U.S. has signaled its continued oversight under the USMCA, underscoring expectations of science-based policy and market access.

For businesses and policymakers, these developments highlight the interplay between sovereign regulatory priorities and trade agreement compliance. Our team at De Minimis Law provides technical guidance on addressing these dynamics, ensuring clarity on obligations and strategic positioning. For tailored advice on USMCA compliance, domestic regulations, or dispute resolution, contact our expert team.

Resources

The USMCA panel's report in Mexico - Measures Concerning Genetically-Modified Corn is available here.

Mexico's proposed constitutional amendment banning domestic cultivation of genetically modified cord is availble here (in Spanish).