Mexican Immigration policy is built into their Constitution!

Adopted in 1917, the constitution of the United Mexican States borrows heavily from American constitutional and legal principles. It combines those principles with a strong sense nationalism, cultural self-identity, paternalism, and state power. Mexico’s constitution contains many provisions to protect the country from foreigners, including foreigners legally resident in the country and even foreign-born people who have become naturalized Mexican citizens. The Mexican constitution segregates immigrants and naturalized citizens from native-born citizens by denying immigrants basic human rights that Mexican immigrants enjoy in the United States.

Summary

In brief, the Mexican Constitution states that:

• – Immigrants and foreign visitors are banned from public political discourse.
• – Immigrants and foreigners are denied certain basic property rights.
• – Immigrants are denied equal employment rights.
• – Immigrants and naturalized citizens will never be treated as real Mexican citizens.
• – Immigrants and naturalized citizens are not to be trusted in public service.
• – Immigrants and naturalized citizens may never become members of the clergy.
• – Private citizens may make citizens arrests of lawbreakers (i.e., illegal immigrants) and hand them to the authorities.
• – Immigrants may be expelled from Mexico for any reason and without due process.

The whole thing can be read here.