Name
Institution
Date
LEGALITY OF THE USE OF ARMED FORCES UNDER INTERNATIONAL LAW
At its core, the United Nations Charter provides for the prohibition against the application of
armed force as one of the primary principles of international law. The principle is provided
under Article 2(4) of the UN Charter, which states that a UN member nation may not threaten
or use force against the territorial sovereignty integrity or political independence of another
member state, or in any manner that contradicts the objectives of the UN. Whereas the term
"armed" or a similar term is not used in Article 2(4), most commentators believe it only
prevents military power, excluding non-military types of the threat of force such as financial
sanctions or cyber warfare.1
As Article 2(4) suggests, the restriction on using force does not apply in all circumstances. A
sovereign nation may use force inside its borders to safeguard its integrity. Nations have
considerable latitude in maintaining their domestic affairs. Even so, it is rarely easy to
distinguish between domestic and international disputes. Several scholars also presume that a
nation can use force beyond its borders in instances that do not jeopardize another nation's
integrity or self-determination.2 Force may be employed for humanitarian reasons or to protect
the citizens of the intervening nation who reside overseas in such instances. The UN Charter
does not recognize these instances as exclusions to the restriction on the use of force.
Furthermore, many acknowledge that it falls under the special category of global jus cogens,
which expresses the critical significance of the restriction as well as its widespread acceptance
by the global community.3 In contemporary politics, the prohibition of the use of force among
nations is one of the guiding principles of the international community.
1
‘Use of Force under International Law’ (Justia9 June 2021) <https://www.justia.com/international-law/use-offorce-under-international-law/> accessed 25 December 2022.
2
Ibid.
3
‘Use of Force, Prohibition Of’ (Oxford Public International Law2019)
<https://opil.ouplaw.com/display/10.1093/law:epil/9780199231690/law-9780199231690-e427> accessed 25
December 2022.
Subsequently, as demonstrated by the Oil Platforms case, the prohibition on the use of force
can serve as a basic legal background for the analysis of other agreements, ensuring their
adherence to international guidelines regarding the use of force. As mentioned above, the ICJ
had to decipher a provision in the Iran-US friendship peace agreement, which allowed each
party to pass legislation required to safeguard its important safety interests. In instances where
that provision is enforced to ascribe motives encompassing the use of armed force, the Court's
view was that it could only contain initiatives in accordance with the general guidelines on the
use of force and self-defence.4
As much as Article 2(4) of the UN Charter prohibits member states from using force against
other member states, the Charter also recognizes self-defence as an exemption to the
prohibition against using armed force. The Charter expressly gives every nation an inherent
right to self-defence if an armed attack is directed towards the member state; the Security
Council has taken the extent to that measures to maintain international peace and security.5
The debate over the nation's use of force is primarily focused on the extent and nature of certain
exclusions to the prohibition. Generally, states trying to justify their pre-emptive use of armed
force, for instance, Russia against Georgia in 2008 and Ukraine in 2014, 6 do so by asserting
that one of the exceptions is applicable instead of disputing the existence of a principle of
international law that requires them to give a justification for each specific act of armed power.
The most well-known rationale for using armed force is the right to self-defence, enshrined in
Article 51 of the United Nations Charter and acknowledged as a principle of customary
4
‘Latest Developments | Oil Platforms (Islamic Republic of Iran v. United States of America) | International
Court of Justice’ (Icj-cij.org2017) <https://www.icj-cij.org/en/case/90> accessed 25 December 2022.
5
‘Chapter VII: Article 51 — Charter of the United Nations — Repertory of Practice of United Nations Organs —
Codification Division Publications’ (Un.org2016) <https://legal.un.org/repertory/art51.shtml> accessed 25
December 2022.
6
‘Use of Force, Prohibition Of’ (Oxford Public International Law2019)
<https://opil.ouplaw.com/display/10.1093/law:epil/9780199231690/law-9780199231690-e427> accessed 25
December 2022.
international law. The above right is widely acknowledged in abstracto to emerge as a
permissive legal rule. Still, its essential prerequisites and the way to define them in a particular
instance remain highly contentious. At its core, the Nicaragua v United States case expressly
recognized that the right to self-defence was an absolute right under customary international
law and the UN Charter. It was emphasized that: Article 51 of the Charter is only relevant when
there is an "innate" or "inherent" right to self-defence, and it is difficult to comprehend how
this could be something other than customary, even though its current substance has been
affirmed and inspired by the Charter...”7
Moreover, the protection of nationals abroad has been appreciated as another justification for
using force. Shaw argues that using force to defend nationals and property located abroad was
explicitly viewed as legal in the 19th century. Numerous incidents emerged to illustrate
recognition of such a position. Since the adoption of the UN Charter, it has become more
contentious since the territorial sovereignty and self-determination of the intended state are
contravened. At the same time, one interpretation of article 51 would refute that an "armed
attack" might take place against persons overseas within the interpretation of that stipulation
because the nation itself must be under attack rather than specific individuals outside the
jurisdiction.8 A widely accepted instance of a nation using force to protect its nationals abroad
was evidenced in 1964 when the United States and the Belgium government, with the consent
of the Congolese government, sent their troops to Congo to rescue its nationals who had been
held as hostages by the rebels. Famously, Israel sent its forces to Entebbe, Uganda, to rescue
7
‘Judgments | Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. United States of
America) | International Court of Justice’ (Icj-cij.org2017) <https://www.icj-cij.org/en/case/70/judgments>
accessed 25 December 2022.
8
Malcolm N Shaw, International Law (Cambridge, United Kingdom New York, Ny Port Melbourne, Vic Delhi
Singapore Cambridge University Press 2017).
its nationals who had been held hostage by Palestinian and other rebels following the hijack of
an Air France airline, which has widely been known as the Entebbe Raid.9
ARGUMENTS ADVANCED BY RUSSIA
The conflict between Russia and Ukraine dates back to 2014, when Russia invaded Crimea.
Russian President Vladimir Putin emphasized the importance of safeguarding the rights of
Russian citizens and Russian-speaking people in Crimea and south-eastern Ukraine. After a
contentious national census, Crimeans decided to join the Russian Federation, after which
Russia legally occupied the peninsula.10 The crisis exacerbated ethnic tensions, and proRussian separatists in the eastern Ukrainian provinces of Donetsk and Luhansk staged their
sovereignty elections two months afterwards. Armed confrontation rapidly erupted in the
territories involving Russian-backed militants and Ukrainian forces. Russia disputed military
engagement; however, Ukraine and NATO confirmed the deployment of Russian troops and
military supplies in Donetsk, as well as Russian cross-border shelling soon following Crimea's
takeover.
World leaders and international institutions like the United Nations and NATO have all argued
that Russia is violating international law by invading Ukraine. They have gone to the extent of
condemning such actions. Nations and experts on both sides have used international law
rhetoric to describe the current situation in Ukraine, from Russia's allegations of "genocide"
and "peace-making" to the denunciation of "blatant acts of aggression" and accusations of war
crimes.
9
‘Entebbe Raid | Summary & Facts | Britannica’, Encyclopædia Britannica (2022)
<https://www.britannica.com/event/Entebbe-raid> accessed 26 December 2022.
10
‘Conflict in Ukraine | Global Conflict Tracker’ (Global Conflict Tracker2022) <https://www.cfr.org/globalconflict-tracker/conflict/conflict-ukraine> accessed 25 December 2022.
Russia and Ukraine are sovereign and independent states and also members of the United
Nations. Thus, they are governed by the UN Charter in Article 2(4), which prohibits its
members from using or threatening to use force. Moreover, the Charter gives them an exception
to the later provision in Article 51, which gives them an inherent right to self-defence in
instances of an armed attack against the states. Therefore, amid the present crisis, Ukraine has
a right to self-defence. However, Russia has advanced several arguments to justify its invasion
of Ukraine.
Firstly, Russia formally provided the basis for its invasion of Ukraine through an address by
Russian president Vladimir Putin. In his address, President Putin relied on the doctrine of selfdefence, particularly by expressly quoting Article 51 of the UN Charter. In its address to the
UN Security Council and the International Court of Justice, Russia declared that its operations
on the Ukrainian territory are "grounded on the United Nations Charter, particularly Article 51
and customary international law.11 Importantly, Russia invoked the inherent right to selfdefence on several grounds, among them being; assertions that US international policy, the
expansion of NATO eastwards, and Ukraine's military programs pose a "very significant
danger not only to Russia's interests but also to the very presence of Russia and its sovereign
rights of individual self-defence. It also contended, under collective self-defence, that it assisted
the Donetsk People's Republic and the Luhansk People's Republic.
The justifications mentioned above by Russia are neither supported by fact nor the law, as
neither of those arguments meets the criteria of international law for self-defence. First,
Russia's emphasis on individual self-defence fails since Ukraine did not launch an "armed
attack" on Russia or any UN member state. Second, Russia's emphasis on collective self-
11
Jus Mundi, ‘Implications of the War in Ukraine under International Law - Part 1’ (Jus Mundi Blog29 April
2022) <https://blog.jusmundi.com/implications-of-the-war-in-ukraine-under-international-law-the-use-offorce-under-international-law/> accessed 25 December 2022.
defence fails since such a right applies only to States rather than to non-State individuals or
organizations. The rationale for the latter is that the provinces of Donetsk and Luhansk are not
recognized as sovereign nations under international law, as defined by the Montevideo
Convention on the Rights and Duties of States.
Notably, Russia raised an argument based on allegations of genocide as the basis of their
invasion of Ukraine. Russia's president, in his address, contended that Russia was protecting
the people exposed to intimidation and genocide for eight years by the Kiev government.12
Despite the argument being thinly veiled to attempt to legitimize Russia's use of force in
international law, Russia has not provided any evidence to back its basis claims of genocide. It
thus would not, in any event, give Russia the authority to invade Ukraine. Even if Ukraine
committed infringements of human rights against Russians in eastern Ukraine, neither the
Genocide Convention nor the UN Charter permits treaty signatories or UN member states to
employ force to avenge genocide or significant human rights violations.13 Thus, the
International Court of Justice will have to decide whether Russia's charges of genocide are true.
Even if Russia could substantiate its charges, they are unlikely to give legal legitimacy to using
force in Ukraine.
The Genocide Convention does not expressly grant a State the ability to force independently
on another nation's territory to avert genocide. Article I include a commitment to "prevent and
punish" genocide, although there is no suggestion that this is meant as an exemption to UN
Charter Article 2(4). Genocide is defined as "acts were done to eliminate, entirely or in part, a
12
Ibid.
‘How Russia’s Invasion of Ukraine Violates International Law’ (Council on Foreign Relations2022)
<https://www.cfr.org/article/how-russias-invasion-ukraine-violates-international-law> accessed 25 December
2022.
13
national, ethnic, racial, or religious group".14 As a result, Russia's attempt to justify its military
action in Ukraine based on the Genocide Convention appears unjustified.
Apart from the Genocide Convention, Russia's claim of genocide could be a concealed allusion
to principles such as humanitarian Intervention, "Responsibility to Protect," or the application
of force to avoid significant violations of a jus cogens norm. Some countries have previously
invoked such principles to support the use of force, for instance, the NATO bombings of Serbia
in 1999. However, they have not been universally acknowledged as customary international
law exemptions to Article 2(4) of the UN Charter. It is possibly because of this rationale that
Russia has not properly established such principles to justify its conduct.15
Conditions on the legal basis for self-defence
The UN Charter has been appreciated to give every member state of the UN the inherent right
to self-defence as provided for under Article 51 of the Charter. In its simplicity, Article 51
requires member states to report to the UN Security Council of their measures with regard to
the use of force under the principle of self-defence. However, in the Nicaragua case, Judge
Schwebel expressly stated that a state cannot be denied, and cannot deny itself, of its inalienable
right to self-defence either individually or collectively because it fails to report to the Security
Council of measures taken in execution of that right.16
It is important to note that the inherent right to self-defence can be traced to the Caroline Case
of 1873, which established the essential grounds for self-defence.17 The grounds have been
universally accepted as forming part of customary international law. In the case, several
14
The Genocide Convention, Article 2.
Supra note 11.
16
Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America)
(Jurisdiction and Admissibility) [1984] ICJ Rep 392.
17
Malcolm N Shaw, International Law (Cambridge, United Kingdom New York, Ny Port Melbourne, Vic Delhi
Singapore Cambridge University Press 2017).
15
grounds for self-defence were established and summarized to include an armed attack under
Article 51 of the UN Charter. Necessity and proportionality were provided for under customary
international law.
Under international law, the Oil Platforms case has been acknowledged for giving a summary
of the grounds for self-defence. As regards the concept of an armed attack, the Court observed
that for a nation to use force to justify self-defence, it has an obligation to show that it was the
recipient of an armed attack, which is related to but not equivalent to the use of force in
violation of Article 2(4). It possesses the burden of proving this. Even so, it is essential to
demonstrate that the nation trying to seek to use force in self-defence has been deliberately
attacked. In deciding on the first ground, the ICJ noted that none of the instances in the case
appeared to have been purposefully and clearly directed at the United States.
In trying to figure out how significant an armed attack should be for a self-defence response to
be legitimate, the International Court of Justice, in the case of Nicaragua v. United States
(1986), decided that an armed attack must be of a definite "magnitude and impact," thus not all
incidents can be classified as armed attacks.18 The ICJ defined the definition of "armed attack"
as "the most serious form of the use of force" without looking deeper into specifics and
interpretations of the significance of the phrase "serious form of the use of force".
The principles of necessity and proportionality are acknowledged as exceptional legal and
pragmatic necessities for the right to self-defence. The necessity presupposes establishing that
the dispute cannot be resolved peacefully. There is a view that the circumstance of total
conviction where no other initiatives could prevent enemy attack also helps justify the
necessity, for instance, when the nation's survival is directly threatened. All other alternatives,
18
Michael N Schmitt, ‘Cyber Operations and the Jud Ad Bellum Revisited’ (Villanova University Charles Widger
School of Law Digital Repository2013) <https://digitalcommons.law.villanova.edu/vlr/vol56/iss3/10/> accessed
25 December 2022.
except the use of force, cannot constructively alter the circumstances. Consequently, the use of
force in self-defence ought to respond to a genuine threat to a nation's survival.
According to the principle of proportionality, the use of force must be restricted to neutralizing
or eliminating the invasion against which a nation is defending itself. As per Cassese, the
principle of proportionality necessitates the insurance of harmony between the harm sustained
by the wrongdoing state and the defensive measures and the goal of compelling the perpetrator
to cease their wrongful conduct.19 Also, the proportionality concept does not demand that the
firearms used for self-defence be similar to those used for invasion.20
Therefore, for the argument of self-defence to be met, Russia ought to support its basis of an
armed attack by Ukraine and the necessity of the armed attack. Lastly, it should show that the
use of force was proportionate to the acts done by Ukraine.
HOW USE OF FORCE OUTSIDE THE CONFINES OF THE CHARTER HAS
CHANGED CUSTOMARY RULES
With two commonly recognized exceptions, the use of force is strictly forbidden under
customary international law and the UN Charter. To begin, the UN Security Council may
explicitly allow the use of force to preserve and re-establish stability and peace. The Security
Council is mandated by Chapter VII of the United Nations Charter to take action in case of a
potential danger to the peace, violation of the peace or aggressive act. Permission of armed
Intervention is one example of such a measure. Furthermore, nations may use force in selfdefence in the event of an armed attack. However, not every use of force constitutes an armed
19
20
Antonio Cassese, International Law. (Oxford Univ Press 2016).
Bruno Simma and others, The Charter of the United Nations: A Commentary (Oxford University Press 2002).
assault. An armed movement must be of a definite gravity to imply the right to self-defence.21
Individuals or groups may exercise their right to self-defence. To be legal, using force as a
response to a military assault should be both necessary and reasonable. It is debatable whether
the right to self-defence includes the right to defend oneself against a military assault by a nonstate actor or the right to pre-emptive self-defence. Similarly, other alleged exclusions to the
obligation to safeguard principles, such as humanitarian law or the application of force, are
being challenged.
Under customary international law, the use of force ought to conform to the guidelines of the
UN Charter or any other recognized international instrument. As much as the UN Charter
provides for the confines under which the use of force must conform, several forms of the use
of force have been accepted as being of ambiguous legality. Among them are humanitarian
interventions, Participation at the request of the sovereign authority, military action,
particularly Intervention by regional organizations without the Security Council's explicit
permission, Intervention to defend own nationals, and Intervention to promote the freedom of
self-determination.
However, a nation's use of armed force to the extent that it contravenes international law will
not be accepted as changing the scope of customary rules nor advancing the jurisprudence of
customary international law. The rationale was evidenced in the Corfu Channel case, whereby
the United Kingdom argued that it had a right to self-protection, involvement and self-defence
under customary international law. The Court struck down the British rationale for Operation
Retail, citing inconsistencies with international law. Surprisingly, the Court did not refer to a
UN Charter guideline, as Albania was not a UN member then. It centred its reasoning on the
concept of sovereign equality, as territorial autonomy is a fundamental foreign policy tenet.
21
‘Use of Force | Rulac’ (Rulac.org2017) <https://www.rulac.org/legal-framework/use-of-force> accessed 26
December 2022.
Concerning the involvement, the Court rejected the British assertion, asserting that it was
believed to be the expression of a strategy of force, such as has given rise to most grave
violations in the past and which could not, whatever the current flaws in the international body,
find a spot in international law.22
In conclusion, the evolution of international law on the use of force, particularly the ICJ's
jurisprudence and state practice, remained the same rule founded by the UN Charter. 23 Thus,
nations can argue customary international law with regard to state practice and opinion Juris in
their application of the use of force, even if it goes against the confines of the UN Charter or
any recognized international instrument. However, the said actions by the states will not in any
way be accepted by the international community as changing the customary rules in the field
governed by the UN Charter.
22
‘Latest Developments | Corfu Channel (United Kingdom of Great Britain and Northern Ireland v. Albania) |
International Court of Justice’ (Icj-cij.org2017) <https://www.icj-cij.org/en/case/1> accessed 26 December
2022.
23
Władysław Czapliński, ‘Customary International Law on the Use of Force’ (2018) 8 Wroclaw Review of Law,
Administration & Economics 97.
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