Constitutional Change in Mexico: Lessons from the Most Amended Codified Constitution

Andrea Pozas-Loyo is a professor at the IIJ-UNAM (Institute of Legal Research), and visiting researcher at the Center for Latin-American Studies, Georgetown University.

Professor Pozas-Loyo was a visiting scholar in March, 2023 at the Center for Constitutional Design at Arizona State University’s Sandra Day O’Connor College of Law.

Mexico’s 1917 Constitution is one of the most amended Constitutions in History, second only to the uncodified 1852 New Zealand Constitution. From its enactment in February 1917 to this day, Mexico’s Constitution has had 748 amendments. In a sense, this is the reversal pattern of constitutional change that characterizes the US, which has one of the lowest amendment rates in the world. In this brief text, I argue that scholars interested in constitutional change from a theoretical and comparative standpoint can extract interesting insights from the Mexican case, as it constitutes an anomaly vis-à-vis two widely held views in constitutional studies.

First, the Mexican case calls into question the claim that under a de jure rigid constitution, political fragmentation decreases the likelihood of constitutional change through amendment. In Mexico, political fragmentation increased the rate of constitutional amendment to a remarkable degree. Second, Mexico’s case calls into question the thesis according to which amendment and interpretation are substitutive means of constitutional modification, in other words, the thesis that claims that the lower the amendment rate, the more likely the process of constitutional revision is dominated by constitutional interpretation and vice versa.  In opposition to this thesis, in Mexico the extremely high amendment rate led the Supreme Court to revise the Constitution in innovative ways through interpretation.

Let us focus on the first anomaly. As political pluralism progressively grew in Mexico, the number of amendments also increased sharply. Prima facie, one might think that this could only happen under a very flexible constitution, but this is not the case. The amendment formula for the Mexican Constitution requires the positive vote of 2/3 of attending members in the House of Deputies and the Senate, plus ratification by half of the 32 State legislatures (including the legislature of Mexico City).

Mexico was ruled by a hegemonic party for seven decades, but in 1988 the PRI (Partido Revolucionario Institucional) lost the capacity to unilaterally amend the Constitution since it no longer retained the 2/3 super-majority in the Chamber of Deputies, and in 2000 the PRI lost the executive for the first time in 71 years. Against all expectations, it was from the 1980s onwards, when political pluralism progressively grew, that the number of constitutional amendments skyrocketed. How can this be?

In the late 70’s and early 80’s the hegemonic party confronted a series of social, political, and economic crises that threatened regime stability. In this scenario, President López Portillo decided to negotiate with the political opposition: the government would agree to open the political arena (just enough) to political participation through constitutional electoral reforms and in exchange the opposition would maintain an acceptable degree of social order.  In 1977, the first of those reforms took place. This reform was seen by the government as a preventive operation capable of providing a means to channel to social and political discontent, while for opposition parties, the reform was a platform to continue their efforts to open the public sphere to political competition. In this way, a series of constitutional reforms opened little by little the political arena while guarantying a relatively peaceful transition. Constitutionalizing the compromises among the three main parties’ elites (PRI, Partido Acción Nacional PAN, and Partido de la Revolución Democrática PRD) meant shielding them from future majoritarian defection. In sum, in Mexico the Constitution played the role of guarantor of credible commitments among political elites, This role was linked to much of the constitutional activity over the years. Therefore, hyper-reformism was critical for transition to democracy in Mexico, and accounting for this role is necessary for understanding why greater political fragmentation in Mexico did not lead to a lower rate of constitutional amendment.

Let us now turn to the second anomaly raised by Mexico’s pattern of constitutional reforms. In Mexico, constitutional hyper-reformism was accompanied by an increase of constitutional interpretation by the Mexican Supreme Court. Hyper-reformism became more intense in 1997 with the arrival of divided government. The amendments passed from 1997 to 2016 amount to 45.2% of all amendments during the entire century. In parallel, data show that constitutional interpretation also increased in the last 20 years. Indeed, the 84% of all constitutional precedents issued by the Court correspond to that 20-year period. In sum, in Mexico the frequency and scope of the Supreme Court’s constitutional interpretation during the hyper-reformist period provide evidence against the validity of the thesis that claims that interpretation and amendment are two substitutive modalities of constitutional change.

To conclude, let me underline two conclusions drawn from Mexico’s case. First, the roles that citizens and elites give to their constitutions can be crucial to understanding constitutional change, or the lack of it, in their jurisdictions. As I have argued, hyper-reformism was socially and politically important in attaining the incremental and largely peaceful Mexican democratic transition after seven decades under hegemonic party rule. Without understanding the important role the Constitution played in this context as the tool that made political commitments credible, one cannot understand how such a high amendment rate was even possible in a context of political fragmentation. Hence, accounting for the different roles constitutions play in different social and political contexts can be crucial to furthering our understanding of constitutional change.

It is noteworthy that the different roles constitutions play in their countries may be included in a much needed theoretical and conceptual refinement of “amendment culture.” As is well known, there is ample evidence showing that countries tend to develop patterns of constitutional change; countries whose constitutions have often been amended will most likely continue on this path, as will countries with low amendment rates. Several authors have suggested that “constitutional culture” may be a variable behind those patterns. But this concept has not been clearly developed. In this connection, the Mexican case suggests that the roles ascribed to constitutions in their jurisdictions may be part of such a “constitutional culture.”

Second, the relation between judicial interpretation and constitutional amendment, as two modalities of constitutional change, is context dependent. In Mexico, a strong and creative judicial interpretation was made necessary by the effects hyper-reformism had on the Constitution; hyper-reformism made the Mexican Constitution a very long, complex and at times inconsistent document. Under this heavily amended Constitution, creative judicial interpretation was required for solving the many conflicts that the very nature of the constitutional text created. Understanding the relation between the different modalities of constitutional change is an important pending research agenda of comparative constitutionalism. While in the US amendment and interpretation do seem to have a substitutive relation, the Mexican case shows that such a relation is not generalizable. 

Finally, the Mexican case reminds us of the perils of overgeneralization in the literature on constitutional change, and the importance of informing our theory building efforts with empirically rich evidence.