Contextualization of the Principle of Proportionality in IHL: Criteria and Examples

by | Mar 6, 2023


A previous post explored the normative nature of proportionality in international humanitarian law (IHL), both as a principle and a rule. Proportionality is a rule relating to the protection of civilians in the conduct of hostilities (art. 51(5)(b), 57(2)(a)(iii) and (b) of AP I). The principle of proportionality is much broader and pervades IHL, including many of the provisions of the Geneva Conventions and Additional Protocols.

This post is devoted to the application of the principle of proportionality (outside of targeting). The post will demonstrate the framework of its application with the logic of its connecting criteria using various examples, some based solely on the law and others based on current events such as the war between Ukraine and Russia.

Application of the Principle of Proportionality

The framework for identifying the application of the principle of proportionality involves the following three steps. The first is to consider whether the provision expressly contains the term proportionality or an analogous term. In French, only one provision of the GCs and its APs contains the term “principe de proportionnalité:” Article 67 of the Fourth Geneva Convention (GC IV). Other provisions contain similar terms (in English) such as in “proportion” (arts. 89(4) and (5), 111(3) of GC IV) or “proportionate” (arts. 51(3), 68(1) of GC IV). This first step acknowledges that when the provisions mention the term proportionality or similar term, it is sufficient to determine that the principle of proportionality applies.

Most of the time the principle of proportionality is not referred to expressly in the provision but rather implicitly. Therefore, its application may also be identified when the provision meets one of four criteria, relating to the nexus to proportionality. One of the criteria is primary and three are subsidiary. The second step of my framework is to determine whether the provision meets the primary criterion, and the third step is, in the alternative, whether it meets one of the subsidiary criteria.

Primary Criterion

The primary criterion is related to the nature of the obligation contained in the IHL rule or provision. Where a provision contains an obligation of conduct, the principle of proportionality applies spontaneously. Where a provision contains an obligation of result, proportionality is initially excluded. Resort must be made to the third step of the framework to determine whether the provision incorporates the principle of proportionality by meeting a subsidiary criterion. These include textual reference, contextual reference, or the relativization of the rule, which will be analyzed below.

The first step is to determine the type of obligation. The obligation of conduct implies an automatic application of proportionality. This reasoning is explained by the nature of the obligations. Indeed, obligations of conduct require the addressee to adopt a certain conduct, which must tend towards the achievement of a certain result. They require states to deploy adequate means, to do their utmost to obtain a certain result. The object of these obligations is a behavior, conduct, an effort, the content of which is determined by a purpose that is not conditional on its achievement. The addressee of an obligation of conduct undertakes to try without ensuring the success of his efforts.

In addition, obligations of conduct have a close link with due diligence, whereas it plays no role in obligations of result. Due diligence is often defined (p. 2) as a “standard of care against which fault can be assessed. It is a standard of reasonableness,” which refers also to proportionality.

On the other hand, unlike obligations of conduct, obligations of result require a specific result. Indeed, this type of obligation requires States to carry out a particular action which is the purpose of the norm. The ICJ (para. 27) had the opportunity to clarify this notion and stated that the obligation of result is “an obligation which requires a specific outcome.” It is an obligation to succeed. The question is not whether and to what extent the State has made efforts to comply with the obligation and achieve the expected result.

Therefore, all IHL rules that are obligations of conduct incorporate the principle of proportionality, while it is ab initio excluded from the obligations of result. In that case if no nexus (subsidiary criteria) to the proportionality is realized, it does not apply at all (examples are cited below). But before admitting its non-application it is necessary to verify that no subsidiary criteria are fulfilled.

Subsidiary Criteria

Subsidiary criteria create an entry point or link for the application of the principle of proportionality in the case of obligations of result. They also exist in obligations of conduct, but they are not decisive. They merely confirm or clarify the application of proportionality.

Subsidiary Criterion 1: The Text

Some terms imply the application of proportionality, such as: adequate, excessive, necessary, and necessity. For example, Article 30(1) of the Third Geneva Convention (GC III) on medical care for prisoners of war requires an adequate infirmary: “Every camp shall have an adequate infirmary where prisoners of war may have the attention they require, as well as appropriate diet.” The word “adequate” means proportionate to the needs and circumstances of the place. One can imagine that the infirmary must be large enough, equipped with the appropriate instruments needed to provide care, in the particular circumstances.

Another example is Article 53(1) of GC III on the working hours of prisoners of war and the use of the term excessive: “The duration of the daily labour of prisoners of war, including the time of the journey to and fro, shall not be excessive, and must in no case exceed that permitted for civilian workers in the district, who are nationals of the Detaining Power and employed on the same work.” In this provision, a mathematical proportionality applies which consists in calculating the daily working time. Knowing that the global average working time per day (men and women combined) is 8.45 hours (p. 11), we can admit that it is excessive if POWs work (including travel) more than 12 hours a day. In this case, the working time of civilian workers in the area, who are nationals of the Detaining Power and who are employed on the same work, must be taken into consideration as a comparison.

Subsidiary Criterion 2: The Context

Sometimes the provision implies the application of proportionality linked to the context. For example, proportionality applies to Article 23(4) of GC III : “Whenever military considerations permit, prisoner of war camps shall be indicated in the day-time by the letters PW or PG, placed so as to be clearly visible from the air.” Proportionality applies when, according to the circumstances, it is not necessary to mark a camp of prisoners of war with the letters PW (for prisoners of war) or PG (for prisonniers de guerre), i.e., in the assessment of military considerations (para. 2050) preventing it.

Subsidiary Criterion 3: The Relativization of the Rule

In many areas of public international law when a rule has an exception or derogation, proportionality intervenes as a condition. This is the case in international trade law (WTO), European Union law, human rights law, the jus ad bellum, and jus in bello. Hence, the relativization of the rule is considered as a nexus to the application of proportionality in IHL. An example is Article 71(1), 2nd sentence, of GC III on correspondence. Proportionality applies to the restriction of correspondence exception. Prisoners of war and internees may maintain relations with the outside world; they have an unlimited right to send and receive letters and cards. Restrictions to this right are subject to a proportionality “balance of interests:” the interests of prisoners of war or internees to correspond without limitation, balanced against the interests of the detaining power in limiting the correspondence for reasons of difficulty of transport or security considerations.

Two examples from the war between Ukraine and Russia help illustrate this criterion more fully. First, the OSCE Report on violations of IHL and human rights law, war crimes, and crimes against humanity committed in Ukraine released on April 13, 2022 states that Ukraine authorities indicated that Russia refused their efforts to receive the bodies of deceased Russian soldiers (p. 9-10). Because it lacked refrigerators to store the dead bodies in its possession, Ukraine reported to the OSCE Mission that the bodies were beginning to decompose and that it would face a serious public health and environmental problem.

Article 17 of the First Geneva Convention (GC I) provides: “Parties to the conflict shall ensure that burial or cremation of the dead, carried out individually as far as circumstances permit, is preceded by a careful examination …. Bodies shall not be cremated except for imperative reasons of hygiene or for motives based on the religion of the deceased….” In addition to the application of the principle of proportionality in Article 17(1) of GC I, because of the obligation of conduct that it entails, the principle applies in Article 17(2) of CG I through the nexus of the relativization of the rule. Burial is the norm (art. 17(1) of CG I), and cremation the exception (art. 17(2) of CG I). The party must have no other choice than to cremate because of, for example, a health threat (imperative reasons of hygiene). The principle of proportionality applies in para. 2 to the cremation prohibition exception because this provision fulfills the subsidiary criterion of the relativization of the rule.

In this case, proportionality implies a balance of interests between the preservation of health (e.g., sanitary threat or health of civilians in the vicinity) and the interest in preserving the dignity of the deceased, i.e., to be buried honorably and to allow the family to mourn in accordance with their beliefs or rites. If Ukraine were to cremate the bodies, then it would have to ensure that proportionality is respected. This implies that it should be used as a last resort and that cremation is justified by imperative reasons of hygiene. Cremation cannot be systematic and carried out on a large scale. It is a matter of taking into account the particular circumstances.

Second, forced deportations from occupied territories have also been reported (OSCE Report, p. 23-24); 500,000 civilians have reportedly been deported from Ukraine to Russia. For its part, Russia denies these accusations. According to Moscow, the Russian military did not forcibly deport Ukrainian citizens to Russia.

In this situation, Article 49 of GC IV provides:

Individual or mass forcible transfers, as well as deportations of protected persons from occupied territory to the territory of the Occupying Power or to that of any other country, occupied or not, are prohibited, regardless of their motive. Nevertheless, the Occupying Power may undertake total or partial evacuation of a given area if the security of the population or imperative military reasons so demand….

The evacuation is an exception to the prohibition of forced transfers and deportations. Hence, the principle of proportionality applies to it. Here it consists of a weighing of interests: on the one hand, the interest of the Occupying Power being able to conduct imperative military operations or to protect the security of the population; on the other hand, the interest of protected persons not to be displaced.

If Russia has carried out forced deportations (including by creating a coercive environment in which civilians had no other choice than to leave) of civilians who had fallen into the power of Russia as an occupying power, this violates IHL and constitutes a war crime. But if Russia as the occupying power had to evacuate, because the security of the population or imperative military reasons weighs sufficiently in the balance to justify displacement, then this would not constitute a violation of IHL. In any case, evacuation outside the limits of the occupied territory, i.e., to Russia, would have required that it was materially impossible to avoid such displacement, which cannot be the case in Ukraine, in view of the dimensions of Ukrainian territories occupied by Russia.

Principle of Proportionality Excluded

Now that we have seen the subsidiary criteria, where a provision contains an obligation of result and does not meet any of the above criteria, proportionality is excluded. A very powerful example is the prohibition against torture provided for in the main instruments of IHL. According to Article 3 common to the GCs, “the following acts are and shall remain prohibited at any time and in any place whatsoever with respect to the above-mentioned persons: (a) violence to life and person, in particular … torture….” This norm is a negative obligation of result and does not fulfill any subsidiary criterion that could justify the application of proportionality. Therefore, it does not apply, and the prohibition of torture is absolute.

Below are some other examples of IHL provisions that contain obligations of result and where proportionality does not apply since they do not meet a subsidiary criterion:

Article 46 of GC I, on the prohibition against reprisals: “Reprisals against the wounded, sick, personnel, buildings or equipment protected by the Convention are prohibited.”

Article 26(6) of GC III, on food: “Collective disciplinary measures affecting food are prohibited.”

Article 49(3), 2nd phr., of GC III, general observations on labor of prisoner of war: “officers or persons of equivalent status … may in no circumstances be compelled to work.”

Article 117 of GC III, on the activity after repatriation: “No repatriated person may be employed on active military service.”

Article 34 of GC IV, on hostages: “The taking of hostages is prohibited.”


In conclusion, the principle of proportionality applies outside targeting, but not to all provisions of the Geneva Conventions and Additional Protocols. It is justified in different ways with, what I called, nexus to proportionality. The first is the nature of the obligation. When the provision contains an obligation of conduct, proportionality is included. Whereas in the case of an obligation of result it is excluded, unless one of the subsidiary criteria is met. These are, as we have seen, the text, context or the relativization of the rule.

We then set out a cascading logic for determining when the principle of proportionality applies in IHL, and we used some examples from war situations, notably between Ukraine and Russia. Lastly, we observed that when a provision contains an obligation of result and none of the three subsidiary criteria are met, proportionality is excluded.


Anaïs Maroonian is a Ph.D. candidate in international humanitarian law at the Faculty of Law of the University of Geneva.


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