The Mexican State contemplates a dualist system for the application of international law (article 133 of the Political Constitution of the United Mexican States (the “Constitution”)). However, there are certain exceptions to such system contemplated in the Constitution:

(i) a pluralist system is implemented with regards to human rights, territorial sea and airspace. In such cases, international treaties entered into by the Mexican State are raised to constitutional rank; and

(ii) a monist system is implemented with regard to the economic exclusive zone of the territorial sea (paragraph IV of article 27 of the Constitution).

Under Articles 1 and 133 of the Mexican Constitution, international treaties to which Mexico is a party form part of the domestic legal order. Article 133 establishes that the Constitution, federal laws enacted pursuant to it, and treaties consistent with the Constitution constitute the supreme law of the Union.

With respect to human rights, Article 1 of the Constitution expressly recognizes the rights contained both in the Constitution and in international treaties to which Mexico is a party. It further requires all human rights norms to be interpreted in accordance with the Constitution and applicable international treaties, favouring at all times the interpretation that provides the broadest protection to the individual (the pro persona principle).

Accordingly, international human rights norms do not, as a general rule, require specific enabling legislation in order to form part of the domestic legal framework or to be relied upon by national authorities and courts. Domestic legislation may nevertheless be necessary to regulate procedures, establish competent authorities, or implement specific treaty obligations in practice.

The Supreme Court of Justice of the Nation (SCJN) has held that human rights recognized in the Constitution and in international treaties form part of a common constitutional regularity framework (parámetro de regularidad constitucional) and are not, as a general matter, related to each other in hierarchical terms. Where different applicable norms or interpretations exist, authorities should apply the one that affords the person the broadest protection, in accordance with the pro persona principle. However, under the SCJN’s jurisprudence, where the Constitution itself establishes an express restriction on the exercise of a human right, the constitutional restriction prevails.