Blog of the International Journal of Constitutional Law

The Enforcement of International Human Rights Standards on Personal Liberty and the Presumption of Innocence in Mexico: When the Supreme Court Became its Own Worst Enemy

Mariana Velasco-Rivera, National University of Ireland Maynooth, School of Law and Criminology; Co-Editor, IACL Blog. Twitter: @marisconsin.

[Editor’s Note: This is one of our ICONnect columns. For more on our 2022 columnists, see here.]

In her forthcoming book, ‘Responsive Judicial Review – Democracy and Dysfunction in the Modern Age’, Rosalind Dixon puts apex courts at the front and center of the endeavor of defending and enhancing constitutional democracy. One of the central premises of Dixon’s argument is that in order to perform such a role, constitutional judges need to be strategic in crafting opinions so as to create legislative-judicial dialogue and, in the last instance, avoid democratic backlash. Recent developments in Mexico illustrate that, when it comes to creating the proper conditions for constitutional adjudication, courts have the potential to become their own worst enemy. To be able to defend and enhance constitutional democracy (in this case, guaranteeing the enforcement of international human rights standards) perhaps judges not only need to be strategic in terms of crafting decisions but also in handling communications regarding their work and how they engage with the public.  

Last September, the Mexican Supreme Court once again came into focus in the context of three high-profile cases, two in abstract review (Acción de Inconstitucionalidad 130/2019 and 136/2019) and one individual constitutional complaint (Amparo en Revisión 355/2021), that involved the possibility of doing away with a problematic landmark judgment (Contradicción de Tesis 293/2011) decided in 2013. The 2013 decision effectively undid a constitutional amendment adopted in 2011 (known as the human rights amendment) that incorporated the notion of a ‘constitutional bloc’—that is, the incorporation of international human rights treaties as part of the constitution. However, after sheer political pressure by the federal government and 19 (out of 32) governors, the Supreme Court postponed the adjudication of these cases.

Specifically, the cases concerned a question regarding the constitutionality of automatic pre-trial detention (prisión preventiva oficiosa) as provided in the national code of criminal procedure (Código Nacional de Procedimientos Penales) and the national security statute (Ley de Seguridad Nacional). Notably, automatic pre-trial detention is constitutionally entrenched. It was constitutionally codified in article 19 as part of an exception regime to the constitutional amendment that introduced the accusatory system in 2008— in theory, a progressive criminal law system that would better protect, among other things, the presumption of innocence. When it comes to the catalogue of crimes identified in article 19, judges do not consider whether pre-trial detention is necessary to ensure a defendant is brought to trial. Instead, detention is ordered automatically for the sole reason of being accused of committing a crime listed in article 19.

Automatic pre-trial detention has become one of the most (if not the most) prominent features of penal policy across presidential administrations in Mexico. To this day, 40.8%  of people in prison have not gone to trial and/or have not been convicted. The catalogue of crimes included in article 19 has been expanded since 2008. Its most recent (and largest) expansion, led by the current government, took place in 2019.

As mentioned at the outset, the Mexican constitution, like many other constitutions in Latin America, provides for what is known as the ‘constitutional bloc’— its article 1 reads as follows:

In the United Mexican States, all individuals shall be entitled to the human rights granted by this Constitution and the international treaties signed by the Mexican State, as well as to the guarantees for the protection of these rights. Such human rights shall not be restricted or suspended, except for the cases and under the conditions established by this Constitution itself.

The provisions relating to human rights shall be interpreted according to this Constitution and the international treaties on the subject, working in favor of the broader protection of people at all times.

In light of article 1, automatic pre-trial detention wouldn’t stand a chance of surviving constitutional review. Automatic pre-trial detention is in breach of the Inter-American Convention on Human Rights and the Inter-American Court of Humans Rights’ jurisprudence regarding personal liberty and the presumption of innocence, as well as against basic principles of liberal constitutional democracy. The issue, however, is that automatic pre-trial detention is constitutionally entrenched in article 19. In theory, the second paragraph of article 1 provides a solution: judges have the obligation to apply the most protective provision. However, a landmark Supreme Court decision effectively destroyed the possibility of operationalizing the constitutional bloc in cases like this and did away with the judges’ obligation to apply the most protective provision. In the Contradicción de Tesis 293/2011 [hereinafter the constitutional restriction precedent], the Supreme Court decided that whenever there was a constitutional restriction on rights, judges should apply it in preference to other provisions.

The three cases at hand presented an important opportunity to overturn the constitutional restriction precedent and fully operationalize Mexico’s ‘constitutional bloc’. However, the opportunity was squandered by a problematic framing of the discussion and a lack of strategy in terms of communications regarding the work of the Supreme Court on the part of the Justice who penned the draft opinion, Justice Luis Maria Aguilar, and the Chief Justice, Arturo Zaldívar.

Derailing the debate

In the draft opinion of the abstract review cases (Acción de Inconstitucionalidad 130/2019 and 136/2019), Justice Aguilar considered that it was necessary to i) overturn the constitutional restriction precedent—which would have required the Court to give prevalence to article 19 in detriment of the Inter-American system of Human Rights and declare the constitutionality of the challenged provisions; and ii) assess the conventionality of article 19 before assessing the constitutionality of the challenged provisions. In so doing, the draft opinion stated that article 19 of the constitution was in breach of the Inter-American system of Human Rights and, as such, should not be applied.

Overturning the constitutional restriction precedent was already a bold move in that it had legitimized what has become a political practice: constitutionalizing policy to avoid judicial scrutiny. However, assessing the conventionality of article 19 (i.e., determining whether the constitutional provision is in line with human rights international standards) as a previous step to apply international human rights standards (through article 1) was a methodological mistake that, in my view, was one of the two factors that derailed the Court’s decision-making process. One of the traditional concerns regarding the relationship between international law and domestic law is that of constitutional supremacy. By assessing the conventionality of article 19, the practical effect is that the constitution ceases to be the supreme law of the land and is replaced by the international treaty in question. In assessing the conventionality of article 19 and disapplying it, the draft opinion was effectively attributing a hierarchical relationship between the constitution and the Inter-American system of Human Rights –whereby the latter is hierarchically superior. Naturally, such a proposal was likely to provoke resistance—and it did.

But there was a second factor that, in my view, made things worse. In a press conference on 17 August 2022, Chief Justice Zaldívar announced that the Supreme Court was set to decide a set of cases of the utmost importance “to determine the unconventionality or not of the automatic pre-trial detention and whether the Constitution can be unconstitutional” (see mins. 07:00-09:00 of the footage). Note that the question of the constitutionality of the constitution (in those precise terms) was not part of Justice Aguilar´s draft opinion. Framing it as such was entirely the choice of the Chief Justice. This, of course, was picked up by the press, the public, the legal community as well as the government. Since that press conference, the debate almost exclusively centered on whether the Supreme Court should or should not declare the “unconstitutionality of the constitution”.

Unsurprising backlash

Unsurprisingly, before, during, and after the court’s deliberations, there was strong resistance to this approach and reactions from the federal government (in particular the President and the Secretary of the Interior) as well as governors and legislators. The Secretary of the Interior, together with the Executive Legal Advisor (Consejera Jurídica) issued a statement calling for the Supreme Court to uphold the constitutionality of the provisions:

The existence of automatic pre-trial detention is essential to guarantee that, when it comes to certain crimes, crime suspects [are] (…) brought to trial…. The aim is to avoid that in retaliation to the detention, [crime suspects] threaten the integrity of crime victims or threaten witnesses or that they continue conducting criminal activities (…).

Leaving the application of automatic pre-trial in the hands of judges would create additional pressure on them and, due to the nature of the crimes to which automatic pre-trial detention is directed, would expose them to corruption and violence.

We ask the highest tribunal of the land to consider, (…), the country’s public safety, the crime victims, the fight against impunity, and the enormous effort that criminal prosecution entails for law enforcement authorities at the federal and local level, and consequently, uphold pre-trial detention as provided by our fundamental law. (Translation is mine.)

On different occasions, President López Obrador doubled down on fearmongering and falsely claiming that the abolition of automatic pre-trial detention would result in thousands of “criminals” set free (see mins. 34:34-1:09 of the footage of this press conference) and the loss of human lives. Moreover, akin to the Secretary of Interior’s press release, 19 out of 32 governors issued a joint statement questioning the power of the Court to “remove or amend parts of the constitution” and calling for the Justices  to strictly observe article 19 and uphold the automatic pre-trial detention:

Removing parts of the constitutional text (…) or modifying the text is NOT among the Supreme Court’s powers. (…) the members of the Supreme Court (…) DO NOT HAVE THE POWER TO (…) AMEND THE CONSTITUTION, even less so when [the constitutionality of] article 19 WAS NOT CHALLENGED (…).

For these reasons, we respectfully call upon … the Supreme Court TO RESPECT THE SEPARATION OF POWERS, STRICTLY OBSERVE THE CONSTITUTIONAL TEXT (…).

We ask [the court] to take into account these considerations so that we can continue to guarantee the peace and tranquility that Mexicans wish for. (Translation is mine. The use of capital letters is from the original statement.)

Because of the methodology chosen by Justice Aguilar, the deliberation in the Supreme Court also focused almost exclusively on this point. After three days of deliberation (and strong political pressure), Justice Aguilar inexplicably decided to withdraw the draft opinion and craft a new one (Justice Norma Lucía Piña, who penned the draft opinions for the individual constitutional complaints did the same). Unsurprisingly, the next day, President López Obrador publicly thanked the Supreme Court for its decision to withdraw the draft opinions because [declaring the unconstitutionality of automatic pre-trial detention] “would have created lots of problems [for the government]”.

Even though the cases were not adjudicated and, therefore, the  Supreme Court did not decide on the constitutionality/conventionality of the constitution, less than a week after the withdrawal of the draft opinions, a jurisdiction-stripping bill was presented in the Chamber of Deputies by Dep. Reyna C. Ascencio (member of the ruling party, MORENA) to ban the court from assessing the constitutionality of the constitution and impose an obligation to observe constitutional restrictions. It is unclear if the sheer political pressure is what explains the withdrawal but the optics in terms of the independence of the Supreme Court are less than ideal. What is clear to me is that the Chief Justice’s framing unnecessarily raised the (already high) profile of the cases and swayed the discussion in the wrong direction even before the court heard the case. If the withdrawal sought to let the waters calm, it remains to be seen if it worked. But things are not looking great. Last week, Justice Aguilar’s new draft opinion was made public, and even though it moves away from assessing the conventionality of article 19, the reaction of the President in terms of fearmongering did not change one bit. It remains to be seen how things develop in the coming weeks.  

This episode speaks in favor of Dixon’s argument in that judges not only need to be strategic in crafting decisions but also extremely careful in how they handle communications and engagement with the public. Far from creating the inter-branch dialogue that Dixon’s responsive judicial review aims at, in this instance, the Supreme Court (in particular the Chief Justice) became its own worst enemy. The Chief Justice provided ammunition for the backlash that followed his press conference, significantly contributing to the creation of a hostile environment for the administration of justice.

Suggested citation: Mariana Velasco-Rivera, The Enforcement of International Human Rights Standards on Personal Liberty and the Presumption of Innocence in Mexico: When the Supreme Court Became its Own Worst Enemy, Int’l J. Const. L. Blog, Nov. 9, 2022, at:


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