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1. Coerced Consent / Unequal Bargaining Power

Mexico was under military occupation when it signed the treaty—U.S. forces had captured Mexico City.

The treaty was signed under duress, which, under modern international law principles (e.g., Vienna Convention on the Law of Treaties, 1969), would render an agreement potentially void.

Key argument: A treaty signed under threat of continued invasion or annihilation is not a free contract between equals.

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2. Unconstitutional Process in Mexico

Mexico's president at the time, Manuel de la Peña y Peña, signed the treaty during a chaotic post-war interim government.

Some critics argue that this interim government lacked legitimacy or full authority to cede more than half of Mexico’s territory.

Domestic opposition to the treaty was intense within Mexico; some Mexican lawmakers and intellectuals argued that such vast land cessions were not constitutionally permitted under Mexican law.

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3. Violation of Indigenous Sovereignty

The treaty transferred lands populated by Native American nations (e.g., Apache, Navajo, Comanche) without consulting or recognizing their sovereignty.

These groups had never recognized Mexican or U.S. authority in the first place.

The argument is that the treaty was a colonial document that ignored the rights of third-party nations, violating principles of self-determination.

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4. Treaty’s Promises Were Broken

The treaty guaranteed the civil, political, and property rights of Mexican nationals in the ceded territories (Article VIII and IX).

In practice, these promises were not honored:

Many land grants were not recognized or were tied up in courts for decades.

Mexican-Americans faced discrimination, disenfranchisement, and dispossession.

Some argue this breach of treaty terms retroactively undermines its legitimacy, or at least calls into question its legal force.

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5. Racial and Expansionist Ideologies

The war and treaty were driven by Manifest Destiny—a racialized ideology of Anglo-Saxon supremacy and territorial expansion.

Critics argue the treaty was a product of imperialism, not a fair international agreement.

It served to legitimize conquest under the pretense of legality.

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6. Lack of Modern Legal Standards

The treaty was signed long before modern international law codified standards for treaty validity, human rights, and self-determination (e.g., United Nations Charter, 1945).

From a modern perspective, the treaty might be seen as violating jus cogens norms (peremptory norms of international law), especially regarding:

Wars of aggression

Forced cessions

Denial of civil rights

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Summary

Argument Basis

Coerced Consent Treaty signed under military occupation

Unconstitutional under Mexican law Interim gov’t lacked full legitimacy

Indigenous Sovereignty Ignored Native nations never consented

Treaty Violations by U.S. Promises to Mexicans in ceded lands not upheld

Racist/Imperialist Motivations Manifest Destiny ideology taints legitimacy

Violates Modern Legal Norms Would not meet standards of Vienna Convention or UN Charter

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Let me know if you want legal citations or court cases where these arguments have been raised (e.g., in land disputes or UN submissions).

(http://www.autoadmit.com/thread.php?thread_id=5735138&forum_id=2#48998740)