Lawfully Exercising the Right to Self-defence under Article 51 of the UN Charter to Recover Occupied Territory

Author Note¹This article relies heavily on a class discussion that took place during the BCL in 2020 during Michaelmas Term. An article was published by our respected teachers, Professor Dapo Akande and Professor Antonios Tzanakopoulos, in 2020 on the EJIL:Talk! blog, and then in 2021 in the European Journal of International Law, the latter of which is referenced in this work and addresses the question in more detail

What say you, then,
To times, when half the city shall break out
Full of one passion, vengeance, rage, or fear?²William Wordsworth, The Prelude.

The United Nations General Assembly Resolution 2625 (UNGA Res. 2625) unequivocally prohibits the use of force to resolve territorial disputes. Such disputes include territories under unlawful occupation and so the prohibition seems to extend to engagement in military operations aimed at recovering occupied land. However, a question arises as to whether a territory whose occupation is a direct result of an unlawful armed attack³The term ‘unlawful’ qualifies ‘armed attack’ to the extent that some occupations may be a direct result of an armed attack in the factual sense of the word, but such armed attacks may not be unlawful as they took place before the Charter prohibition on the use of force came into effect. See: Dapo Akande and Antonios Tzanakopoulos, ‘Use of Force in Self-Defence to Recover Occupied Territory: When Is It Permissible?’ (2021) 32 European Journal of International Law 1299, 1301. also falls under this prohibition. Are such instances to be distinguished so as to form an exception to the general rule contained in the UNGA 2625, or are they distinct disputes that simply do not fall under the remit of the prohibition contained in the UNGA 2625 at all?

This issue is pertinent for two reasons. Firstly, there are many territories across the world that are occupied, and such territorial disputes naturally inform state interactions. In many cases, these unresolved disputes continue for decades and affect states’ progress, both at a domestic level and at an international level, especially when occupation usually arises with regard to territory situated between neighbouring states. More crucially, occupations affect the individuals living under such conditions and who are often deprived of their basic rights and security, as occupying powers do not always comply with the law of occupation. Secondly, if an occupied territory whose occupation is a direct result of an unlawful armed attack does not fall under the umbrella of ‘territorial disputes’ contained in the UNGA 2625, then the occupied state may legally exercise its right to unilateral and/or collective self-defence against the occupying power(s) under Article 51 of the UN Charter in order to recover its territory.

This article argues that occupations resulting from unlawful armed attacks are indeed distinct disputes that do not fall under the prohibition contained in the UNGA 2625, and the occupied state may therefore legally exercise its right to unilateral and/or collective self-defence against the occupying power(s) under Article 51 of the UN Charter to recover its territory. This is evidenced by first distinguishing between two types of occupations: those resulting from an armed attack and those resulting due to some other cause. Then, the notion of a continuing armed attack is addressed, which leads to the determination that occupations that are a direct result of an armed attack are continuing armed attacks, and so long as the occupation continues, the armed attack also continues. Finally, the article assesses the question as to whether an occupied state loses its right to self-defence due to the passage of time between the use of force in the initial armed attack resulting in the occupation, and the use of force in self-defence at a later point in time. It concludes that such a state does not lose this inherent right simply due to a prolonged occupation even if the occupation effectively changes the status quo of the occupied territory.

An Exception or a Distinction?

Article 2(3) of the UN Charter provides that all states shall settle their international disputes by peaceful means, which follows from the prohibition on the use of force contained in Article 2(4) of the UN Charter. The Friendly Relations Declaration (UNGA Res. 2625) cements the Charter prohibition, specifically highlighting that territorial disputes must not be settled through use of force. It reads, in relevant part:

Every State has the duty to refrain from the threat or use of force to violate the existing international boundaries of another State or as a means of solving international disputes, including territorial disputes and problems concerning frontiers of States.⁴UN General Assembly, Declaration on Principles of International Law concerning Friendly Relations and Cooperation among States in accordance with the Charter of the United Nations, 24 October 1970, A/RES/2625(XXV).

However, scholars argue that a distinction must be drawn between territorial disputes on the one hand, and armed attacks that result in occupation on the other.⁵Dapo Akande and Antonios Tzanakopoulos, ‘Use of Force in Self-Defence to Recover Occupied Territory: When Is It Permissible?’ (2021) 32 European Journal of International Law 1299, 1301. They note the difference between the two situations: the first is one in which, for example, a state justifies their use of force on the basis of alleged title to territory. Such a situation falls under the prohibition of resolving territorial disputes through use of force. The second is one in which a state carries out an armed attack which results in the occupation of another state’s territory. Whilst the title of such a territory may remain in dispute and would need to be resolved through peaceful means, that an armed attack has occurred gives rise to the right to use force in self-defence.⁶ibid, 1302.

In other words, if a state uses force in self-defence against an armed attack that resulted in occupation, then such a use of force would be lawfully exercised under Article 51 of the UN Charter, which is an exception to the general prohibition on the use force contained in Article 2(4) of the UN Charter. Such a use of force would not be exercised as an exception to the general rule contained in the UNGA Res. 2625 comprising that territorial disputes cannot be settled through use of force, and neither would it operate as a new exception (i.e. an exception that is not already present in the Charter framework) to the prohibition on the use of force contained under Article 2(4) of the UN Charter.

One may question the viability of the above distinction. That is, whether it is factually possible to occupy a territory without resorting to use of force or through a lawful armed attack? Kennedy notes that there are two facets to a successful legal distinction: the first is that it must be possible to make a distinction, and the second is that the distinction must make a difference.⁷Duncan Kennedy, ‘The stages of the decline of the public/private distinction’ (1982) 130 University of Pennsylvania Law Review 1349, 1349. With respect to the first, there are numerous examples in pre-Charter history wherein states occupied territories before the prohibition on the use of force came into effect. Whilst the legal terminology of ‘states’ and ‘occupation’ may have been non-existent, the facts on the ground prove that such situations existed. With respect to the second, the difference that the distinction makes has been outlined in the preceding paragraphs which highlight the possibility of using force in one situation, and its prohibition in the other.

The Criteria of Self-defence

In order to lawfully exercise a right to self-defence under Article 51 of the UN Charter, three criteria must be fulfilled: (1) there must be an armed attack, (2) it must be necessary to use force in the exercise self-defence, and (3) the use of force in self-defence must be proportional. This article is concerned with the first two requirements and will address each in turn.

The Existence of an Armed Attack

Some scholars argue that an unlawful occupation is not, in and of itself, a continuing armed attack.⁸Tom Ruys and Felipe Rodríguez Silvestre, ‘Illegal: The Recourse to Force to Recover Occupied Territory and the Second Nagorno-Karabakh War’ (2021) 32 European Journal of International Law 1287, 1290. This argument is partially based on a textual analysis of Article 51 of the UN Charter, which reads, in relevant part:

Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations… .⁹United Nations, Charter of the United Nations, 24 October 1945, 1 UNTS XVI.

The word ‘occurs’ in the above text is interpreted by these scholars as meaning that an armed attack must occur at some certain point in time (i.e. when the occupation commences) and cannot be continuing. This reasoning is criticised on the ground that the word ‘occurs’ does not linguistically confine the attack to a specific point in time. It only means that such an attack must have occurred and/or must be occurring. The text does not set out the duration of an armed attack: it states ‘if’ an armed attack occurs, not ‘when’ it occurs.¹⁰Dapo Akande and Antonios Tzanakopoulos, ‘Use of Force in Self-Defence to Recover Occupied Territory: When Is It Permissible?’ (2021) 32 European Journal of International Law 1299, 1304.

More pertinently, such scholars also fail to address the key question: whether an occupation that is the direct consequence of an armed attack constitutes a continuing armed attack, as opposed to simply whether an unlawful occupation, regardless of how the occupation came about, constitutes a continuing armed attack.  The UNGA Res. 3314 on the Definition of Aggression¹¹UN General Assembly, Definition of Aggression, 14 December 1974, A/RES/3314. and the practice of the ICJ provides some guidance on this issue.

Article 3(a) of the UNGA Res. 3314 states that the following qualifies as an act of aggression:

The invasion or attack by the armed forces of a State of the territory of another State, or any military occupation, however temporary, resulting from such invasion or attack, or any annexation by the use of force of the territory of another State or part thereof…

In the cases of Armed Activities¹²Armed Activities on the Territory of the Congo (Democratic Republic of the Congo v Uganda) (Merits) (2005) ICJ Reports 168, [146]. and Nicaragua,¹³Armed Activities on the Territory of the Congo (Democratic Republic of the Congo v Uganda) (Merits) (2005) ICJ Reports 168, [146]. the court specifically referred to the definition of aggression contained in the UNGA Res. 3314 in order to determine whether the use of force in these cases amounted to an armed attack. Although the court did not explicitly state that ‘aggression’ under the UNGA Res. 3314 and ‘armed attack’ under Article 51 of the UN Charter have the same meaning, the consistent use of the definition of aggression by the court when ascertaining whether an armed attack has taken place highlights that the court deems the two related, if not practically equal.¹⁴Dapo Akande and Antonios Tzanakopoulos, ‘The International Court of Justice and the Concept of Aggression’ in Claus Kreß and Stefan Barriga (eds), The Crime of Aggression: A Commentary (CUP 2016) 214, 222-223. Thus, if the UNGA Res. 3314 holds that occupation resulting from an invasion or an attack is ‘aggression’ and must be of a continuing character, and the attack that leads to the occupation is an ‘armed attack’ within the meaning of Article 51 of the UN Charter, then it follows that as the long as the occupation continues, the armed attack also continues.¹⁵Dapo Akande and Antonios Tzanakopoulos, ‘Use of Force in Self-Defence to Recover Occupied Territory: When Is It Permissible?’ (2021) 32 European Journal of International Law 1299, 1303.

The Requirement of Necessity

Necessity in self-defence is generally understood as referring to the dual requirements of immediacy and using force as a last resort. With regard to the requirement of immediacy, even if an occupation is a continuing armed attack, some scholars argue that the right to self-defence lapses after the passage of (some uncertain) time.¹⁶Tom Ruys and Felipe Rodríguez Silvestre, ‘Illegal: The Recourse to Force to Recover Occupied Territory and the Second Nagorno-Karabakh War’ (2021) 32 European Journal of International Law 1287, 1294. More specifically, they hold that if a state does not respond ‘within a reasonable period of time’ to another state’s armed attack aimed at occupying part of the former state’s territory, then the former state loses its inherent right to self-defence and cannot exercise this right at a later time to recover its territory.¹⁷Constantinos Yiallourides, Markus Gehring, and Jean-Pierre Gauci, ‘The Use of Force in Relation to Sovereignty Disputes over Land Territory’ (BIICL 2018), [158]. If such a state wishes to exercise its right to self-defence ‘once the hostilities have ceased and there has been a prolonged absence of fighting’, then there must be a new legal basis under the jus ad bellum beyond the initial armed attack resulting in the occupation, such as an authorisation to use force by the United Nations Security Council (UNSC) or a new armed attack which would reactivate the right to self-defence.¹⁸ibid, [161].

However, such contentions are vague and ambiguous. Scholars of this opinion fail to identify the exact point in time wherein the right to self-defence ceases. It is unclear what they consider ‘a reasonable period of time’, or how long is required to establish a ‘prolonged absence of fighting’. Moreover, that a territory is occupied as a result of an armed attack, and the armed attack continues so long as the occupation continues, means that the immediacy requirement is met.

As for the requirement of last resort, it is arguable that the precise fact that a territory is under occupation for a prolonged period of time following an armed attack evidences that the state using force in self-defence to recovers its land after so many years has no other means to bring the occupation (and therefore, the armed attack) to an end. Thus, the passage of time supports, rather than negates, the right to self-defence.¹⁹Dapo Akande and Antonios Tzanakopoulos, ‘Use of Force in Self-Defence to Recover Occupied Territory: When Is It Permissible?’ (2021) 32 European Journal of International Law 1299, 1306.

Conclusion

Concluding, self-defence may be lawfully exercised with respect to occupied territories wherein the occupation is a direct result of an unlawful armed attack. To assert otherwise is to render the Charter framework concerning the prohibition on the use of force and the express exception carved for self-defence as a tool that is only available for powerful states who possess the ability to respond immediately against occupying powers. Following this line, if a small state that possesses neither the military power and nor the support of another state, is occupied following an armed attack, then they have no right to self-defence against the initial armed attack… ever. This approach is unrealistic and makes it nigh on impossible for smaller states to effectively respond against aggressor states. The issue is not that occupied states may feel ‘unfairly disadvantaged’ if they do not possess the means to retaliate against occupation (resulting from an armed attack) within a limited period of time,²⁰Tom Ruys and Felipe Rodríguez Silvestre, ‘Illegal: The Recourse to Force to Recover Occupied Territory and the Second Nagorno-Karabakh War’ (2021) 32 European Journal of International Law 1287, 1296. but rather, why should such states be disadvantaged at all?