Foundations of Mexican law: Spanish colonial law, independence and the Constitutions, the Constitution of 1917, the sources and hierarchy of law, the civil law tradition and legal pluralism

Colonial law. After the Spanish conquest (1521), the territory became New Spain. Castilian law applied, together with a special body of law for the Indies (the Recopilación de Leyes de los Reynos de las Indias, 1680) and local custom, including some indigenous customs that the Crown tolerated. Royal courts (the Audiencias) applied this law, and the Church had its own courts. The system was Roman-Spanish civil law, with learned jurists and written codes, not the common law.

Independence and the liberal constitutions. Independence was achieved in 1821. The Constitution of 1824 created a federal republic, and the Constitution of 1857 and the Reform Laws established liberal principles: individual rights, the separation of Church and State, and a civil register. Codification followed in the nineteenth century, using the French Civil Code and Spanish models, and the Federal Civil Code of 1928 (in force from 1932) is the model for most modern codes in the country.

The Revolution and 1917. After the Revolution of 1910, the Constitution of 1917 was adopted. It is one of the first constitutions in the world to include social rights: Article 27 on land and natural resources, Article 123 on labour and the rights of workers, and free secular education. It has been amended hundreds of times, so a current text must always be checked.

The Constitution is the supreme law (Article 133), and any law or act that conflicts with it can be challenged in court. Treaties signed by the President and approved by the Senate are also supreme law when they are in accordance with the Constitution. Since the reform of 2011, human rights in the Constitution and in the international treaties to which Mexico is a party are protected together (Article 1), and officials must apply the interpretation that protects the person most broadly, the pro persona principle, though the Supreme Court has held that express constitutional restrictions prevail.

Federal and state law. Federal laws and state laws are made by different legislatures. Powers not given to the Federation belong to the states (Article 124), and a distinctive feature is the general law (ley general) that the federal Congress issues on a subject for all levels of government, such as the General Law on Responsibilities and the General Law on Transparency. Judicial precedent (jurisprudencia and precedentes) created by the Supreme Court and the collegiate circuit courts binds lower courts in the cases the law specifies. Custom and doctrine are secondary sources.

Civil law in practice. Law is found mainly in codes and statutes, which judges apply to the facts. Courts are not bound by a doctrine of precedent in the common law way, except where the law gives binding force to a line of decisions, and notaries and registries play a central role in property and company law. Procedure is increasingly oral and adversarial, especially in criminal matters (Module 8).

Legal pluralism. Article 2 of the Constitution recognises that Mexico has a multicultural composition based on its indigenous peoples, who have the right to self-determination within the unity of the State. Indigenous communities may apply their own normative systems to resolve internal conflicts and choose their authorities, provided that they respect the Constitution, human rights and, in particular, the dignity and rights of women. Afro-Mexican communities were recognised in the Constitution in 2019. Module 3 explains how this works in practice.

• Check the level. Ask whether the answer comes from the Constitution, a federal law, a state law or a municipal regulation.
• Check the date. The Constitution and many laws were reformed recently (for example the judicial reform of 2024 and the amparo reform of 2025).
• Check the language. Official documents and court proceedings are in Spanish; a sworn translation is usually needed for foreign documents.