Legality of a use of force and the practice of states. What can be expected in the next two decades?

Autor:Dojas, Alberto E.

I would like to express my sincerest gratitude to Professor August Reinisch for his invitation to address such a distinguished audience in the prestigious University of Vienna Law School. I feel truly honoured to have been provided with the opportunity to maintain a dialogue and exchange ideas with such expert audience.

During a round table held here last year, I had the opportunity to mention to Professor August Reinisch my idea of presenting my preliminary findings on a methodology aiming at understanding how States attribute legality to a given use of force to an expert audience. Such presentation and exchange of ideas, by focusing on the application of such methodology to current incidents, would enable me to assert its validity, identify its limitations, constraints, shortcomings and inconsistencies, and further review and refine it accordingly.

I'm also in debt to Peter Bachmayer, Christina Binder, Brigitte Weidinger and Scarlett Ortner, who very kindly assisted me to make this event possible. I want also to express my gratitude to Niels van Tol, Librarian at the Peace Palace Library in The Hague, who helped me without dismay find books and copy articles on this subject, as well as to Evangelia Linaki, for developing the slides for this presentation and editing the final version of this text.

The views expressed herein are strictly personal and should not be considered as reflecting an official view of any institution to which I may be affiliated with. Cases are analyzed just for academic purposes and, thus, such analysis should not be interpreted as an intention to promote any particular idea, opinion or judgment on political or other issues of any country, entity or group of individuals.

As you constitute an expert audience on this subject and our time is quite limited, I will not describe or explain the content of legal or political categories, except when it may be absolutely needed. I will also not refer to the controversies that are well known in the works and teachings of qualified publicists, to which I will refer as "doctrine" throughout the presentation. As much as possible, I will use the terms in the most acceptable or widespread interpretation.


    * Regularities (that can be extracted from the analysis of the practice of States on how they attribute legality to a use of force)

    * Paradigms (historical evolution of attribution of legality)

    * 2015 (current situation)

    * Next 20 years (what we can expect)

    * Drivers for change (that can affect the future paradigm)


    In a book published in Spanish in 2011, whose title may be translated as "Threats, Responses and Political Regime. Between Self-Defense and Preventive Intervention" (1), I tried to explore, among others, four main issues that constitute the first part of this presentation:

    * What is the process by which States make their attribution of legality to a use of force?

    * Are there some regularities or patterns that can observed in the practice of States?

    * If yes, what could be the methodology to predict how States will attribute legality to a use of force?

    * What elements are taken into by States when they classify a use of force as legal or illegal?

    The response to these questions can be found at the crossroads of different disciplines (eg. International Law; International Relations; Political Science; Diplomatic Studies; Sociology; Philosophy).

    What is "practice of States" in this context?

    Within the given context, "practice" not only refers to the technical expression in International Law, according to which State practice is an element used to prove the existence of customary law (2), but also to a behavioural approach on how and why States affirm that a use of force is legal or illegal, which, in turn, affects their behaviour in the international arena and in international organizations.


    The analysis of the legality of a use of force has undergone a process of increasing complexity.

    At the beginning of human society, although some moral and religious norms were established, there were no legal restrictions to the use of force between societies:

    X uses force

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    The first models that tried to establish whether a use of force was legal or illegal were constructed from the assumption that a use of force ought to be defined in similar terms as an offence under criminal law, and then attributed to a State. Thereafter, considering the circumstances of the case, the State's international responsibility could be established, enabling, thus, to qualify the use of force as legal or illegal.


    A further development occurred when the analysis started taking into account both actors in a given use of force: the one that used force and the other that suffered the attack. At a certain point, the actions and motivations of both parts were considered as circumstances affecting the legality of a use of force.


    The model was refined again when the analysis of the circumstances lead to consider that, in fact, it was required to look at the legality of both the threat of one actor and the response of the other.



    Looking at the scheme below we can understand that the legal categories that have been used historically to attribute legality or illegality to a use of force are based on the opposition between self-defence and aggression, that is to say, to the threat and the response. As self-defense is an expression of an inherent right to survival, the analysis is directed at the legality of the first use of force (the threat), which may trigger a subsequent reaction (the response).

    The United Nations (UN) Charter provisions on the use of force were drafted having in mind the experience of the League of Nations, the Briand-Kellogg Pact and the lack of observance of the basic assumption that threats and uses of force were prohibited. Most importantly, they were intended to reassure the main objective of avoiding military confrontation between the great powers that emerged after World War II. Usual categories of use of force remained the basis on which the whole system of international security was built in San Francisco.

    It was the maximum agreement that could be reached at that time. Unfortunately, some very important aspects were kept within the margins of a certain ambiguity:

    1. The undefined terms of "armed attack" and "threat" that are crucial for the interpretation of the scope and limits of the legal regime on the use of force.

    2. The two conflicting ideas contained in Article 51 of the UN Charter:

      --On the one hand, that self-defense was only authorized [if an armed attack occurs].

      --On the other, that [Nothing in the present Charter shall impair the inherent right of individual or collective self-defense].


      --These two competing elements paved the way for the "strict" and "broad" interpretations of self-defense.

    3. The lack of provisions on the so-called "precautionary self-defense" (3), and the legality of a response to a threat that may be carried out in the very near future, whose legality is based on the broad interpretation of Article 51 of the UN Charter.

      Usual categories of threats and responses Threat Response Nature Variations Requirements Nature Carried armed attack a) illegal armed attack Self-defence (Art. 51); out b) other acts contained in the Definition of Aggression (Res. 3314); c) other acts accepted by the practice of States d) seriousness of damage caused Imminent classic-period a) inevitable damage Precautionary formula b)aggressive intention self-defence c) gravity d) damage to the invoking Stale Webster a) overwhelming formula b) no time for deliberation c) no chance to choose means of response doctrine of attack started, nor yet interception completed doctrine of a) attack in the process anticipation of being launched b) attack inevitable doctrine of a a) attacks which are part sequence of of a series of attacks prevention repeated over time b) imminent attacks already announced Possible prevention a) armed conflict Preventive inevitable self-defence b) the threat will be greater in the future Non- peaceful No threat of furure Aggression existent conduct attack exists Response Nature Variations Requirements Current legality Carried armed attack a) necessity legal b) proportionality out Imminent classic-period a) necessity generally illegal formula b) proportionality Webster legal formula doctrine of legal interception doctrine of disputed anticipation doctrine of a disputed sequence of prevention Possible prevention proportionality generally illegal Non- peaceful armed attack Illegal existent conduct Thus, although there was no doubt that when an armed attack had already been carried out it was legal to respond in self-defense if conditions like necessity and proportionality were met, the different alternatives of precautionary self-defense could not reach a similar widespread acceptance.

    4. The case of a preventive use of force intended to better respond to an armed conflict considered inevitable --although used quite often--was not considered.

    5. On the other extreme of self-defense, aggression was clearly regarded as illegal, but the definition of its exact scope took quite some time to reach an extended agreement. The practice of States also broadened further the range of armed threats:

      Aggression (Resolution 3314)

      * Invasion, attack, military occupation or annexation by armed forces.

      * Bombardment or use of weapons.

      * Blockade of ports or coasts.

      * Attack on land, sea or air forces and fleets.

      * Use of armed forces within the territory of another State.

      * To allow its territory to be used by another State for perpetrating an act of aggression.

      * The sending of armed bands, groups, irregulars or mercenaries, or its substantial involvement therein.

      Other acts regarded as armed...

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