Is prohibition of the death penalty becoming customary international law?

Shola Namazova, LLB student, ADA University

Keywords: death penalty, customary international law, state practice, opinio juris, human rights

Illustration credit: Aytan Malikova

In August 2025, Byron Black was executed in Tennessee, United States, despite his health condition which could make his death particularly painful.This shocked the world, drawing the attention of human rights activists and international organizations — not only because of the violence it constituted, but also from the viewpoint of the evolving international legal practice against the use of capital punishment. The case of Byron Black is more than just a tragedy; it further highlighted the ongoing tension between the domestic laws supporting the use of the death penalty and the evolving international practice against it.

The international response and the global trend in favour of abolition raise a critical question: Is it possible that the abolition of the death penalty meets the criteria to be considered a norm of customary international law? I conclude that while the trend is evident, the persistence of major powers in using the death penalty and the lack of opinio juris prevent the formation of customary international law — at least for now.

What is needed for a customary international legal norm ?

For a certain behaviour to become a customary international legal norm, it needs to be so widespread that it becomes legally obligatory. The criteria are the existence of extensive and virtually uniform state practice, combined with opinio juris, which is a state’s general recognition that performing this practice is legally obligatory (North Sea Continental Shelf, Judgment, I.C.J. Reports 1969, p.3). This blog will analyse whether abolition of the death penalty meets these criteria.

Consistent State Practice

For a behaviour to be considered a norm, the foundational requirement is the practice of this behaviour by a significant number of states. There is undeniably a growing trend encouraging abolition, but the requirement of consistent state practice is far from being met. Since 1989, a protocol to the ICCPR aimed at abolishing the death penalty has been ratified by 92 states, including every state in Europe, Australia, New Zealand, the majority of states in Latin America, some countries in Africa such as South Africa, and several countries in Asia such as Azerbaijan , Turkmenistan, and Mongolia.

However, this still falls short of the widespread participation required for establishing consistent state practice. State practice cannot be achieved if there are a substantial number of persistent objectors, which are the states strongly opposing it. Strong opposition coming from persistent objectors such as China, Iraq, and Saudi Arabia, which still carry out executions, is delaying the formation of widespread state practice. Additionally, 27 states in the United States and the US federal government still use the death penalty.

However, there is a growing increase in support for abolition that signals that state practice is in the process of formation. So far, 113 countries have abolished the death penalty for all crimes in their domestic legislation. While the retention of the death penalty by some states delays the formation of a norm, it appears that the use of the death penalty by those states is also declining. Only 15 countries carried out executions in 2024, compared with 25 countries in 2004.

Opinio Juris

The second foundational requirement for a customary international law norm is opinio juris. The consistent state practice must form not because of habit, frequency, or any other reason, but because states believe the conduct is legally obligatory.

Abolition of the death penalty is embedded in European regional law. The European Court of Human Rights has held that the use of the death penalty is a violation of the prohibition of torture and the right to a fair trial (Soering v UK (1989) 11 EHRR 439).This indicates that there is a regional consensus prohibiting the use of the death penalty in Europe.

However, the opinio juris requirement is not met at a global level. Recently, a UN resolution was adopted with 130 votes in favor and 32 against the prohibition of the death penalty. While this reveals that many states supported the abolition of the death penalty, retentionist states such as the US explicitly maintain that imposing the death penalty is a sovereign right.

Moreover, some countries, such as Sri Lanka, have suspended the death penalty and then reintroduced it, which shows that these countries do not feel legally obliged to abolish this practice.

While it is accurate to state that there is consensus to abolish the death penalty in Europe, strong opposition from certain states in parts of Asia, Africa, and the Americas prevents the formation of opinio juris.

Abolition from the perspective of Human Rights

While the requirements for the formation of a norm of customary international law are not completely met yet, the abolition of the death penalty has normative weight from the perspective of human rights.

Capital punishment contradicts the inherent right to life, which is protected in the Universal Declaration of Human Rights and in the constitutions of many states worldwide. Conventions which prohibit torture (ICCPR, CAT) also apply since the death penalty can prolong death, causing suffering. 

The stance of international organisations such as the International Criminal Court further supports the abolition of the death penalty. Such contradictions with human rights suggest that while the requirements for formation of customary international law are not fully met, it is likely that the incompatibility with human rights norms will accelerate the crystallization of the custom.

Conclusion

Although there is a global trend toward prohibition, abolition of the death penalty has not yet crystallized to become a customary international legal norm. This is prevented by the strong objectors and continued use of the death penalty in retentionist states.

However, the growing support and formation of regional custom against the death penalty in some regions of the world along with the alignment of abolition with the intrinsic values of humanity suggests that consistent state practice and opinio juris are in the process of formation. Therefore, while it is obvious that crystallization is unlikely in the near future considering the opposition from some states, increasing support gives hope that a customary international legal norm prohibiting the death penalty will be crystallized in the future.