by Agrim Jain


The world before establishment of United Nations was an entirely different world especially when we refer to the situations of war between the countries as the situation before establishment of the organization was that the countries were left to decide on their own to take decision which they deem fit according to the situation at hand. The only guiding factor in terms of launching of war against one state was that whether the war initiated was on “just” or “unjust” basis, but this discretion gave rise to another issue which was the determination of the subjective criterion on the basis of which the war was to be termed either as “just” or “unjust” war. Thus, the states at their own discretion could launch war against states to promote their own selfish interests and tried to justify it as a “just war” and it is due to the factors such as confusion about what is just or unjust, absence of proper code of conduct for war and lack of strong organization to govern states and implement International Laws, could be attributed to lead world to dire consequences in the world as whole, such as the “World War– I and World War- II”, which in particular had led to the demolition of the “League of Nations”. The World War-II in particular is said to be a result of inability of the League of Nations to function smoothly in the society while discharging its functions mainly due to the factors such as that all the decisions to be adopted had to be taken unanimously, which was rarely ever the situation at that time and also one more important factor that led to collapse was lack of great powers participation. It was after the collapse of League of Nations that there were calls for establishment of a more proper organization, such as the “United Nations” which was established on 24th October, 1945 to govern countries in international arena and also take steps toward effective implementation of the International Laws. It is United Nations which after establishment is responsible for regulating the conduct of war between the countries through the provisions laid down under charter of “United Nations”. The first provision under the Charter is Article 2(4) of the charter, which has prevented the states to use or threaten to use force in their international relations with any other state as a result of which interfere with the political or territorial integrity of the other state. While it is understood that the charter of United Nations through Article 2(4)has prohibited the state from using force against other states on the same hand the Article 51 of the Charter has provided the state with the right to use self- defense in case of aggression by another party, but this right is only available in case of some special circumstances, that is also upon fulfilment of certain conditions and also it is noteworthy that in name of self- defense no state can violate rights of the other state.

Though, in this paper we are mainly concerned with understanding the concept of use of force as provided under Article 51 of United Nations Charter[i], but to gain an understanding it is also important to understand the earlier position in brief. Thus the two main periods of history which we are going to read about are as following.

  1. Position Before 1945:

It is very clear that the law related to use of force by states prior to 1945 had not been developed and as such there was no proper code of conduct to govern the use of force as well. The basic things relating to the same were as following:

  • The just war doctrine;
  • Positivism and sovereign rights of state to resort to war;

This is not to say that before 1945 there were not any as such attempts to restrict use of force. The attempts at that time were mainly through the efforts of:

  1. Covenant of League of Nations;
  2. General Treaty for renunciation of war (Pact of Paris) Kellogg- Briand Pact,1928
  • Position after establishment of United Nations in 1945:

It is a known fact that the League of Nations had proved to be unsuccessful in its attempts to prevent states from resorting to war and in that time even not a single proper code of conduct or proper legislation could be enacted to govern the issue of use of force in international arena and furthermore it was the inability of League of Nations which was attributed for happening of World War-II. Thus, it was only after collapse of the League of Nations that the United Nations was established and that it has dealt with the issue of use of force in its charter as well. The provisions in UN Charter dealing with use of force are as the following:

  1. Article 2(4) of Charter;
  2. Article 51 of Charter.

Article 2(4) of UN Charter:

This article which is referred to as providing of collective security system has refrained the states in their international relations to threaten or use of force against the territorial integrity or political independence of any state or in any other manner inconsistent with the purposes of United Nations[ii]

Meaning of use of force or threat to use of force:

The provisions of article 2(4)[iii] have gained quite a lot of attention possibly due to the absence of word “Armed” before force in provision or even because of the non clarity of the scope of the term “threat of use of force” used in the provision.

The question that arises is that does the Article 2(4) of Charter envisages other types like the imposition of economic sanctions along with armed forces in the definition of the word force as well. The answer to this question is simple that the article 2(4) of Charter is limited in scope in this regard and it only considers armed or military force as a force and no any other kind of force in terms of economic or political pressure is accepted.

Threat of use of force:

The provision has taken into account not only actual use of force but also even threat of use of force has been accounted under the provisions of the article. Threat of force basically means an ultimatum announcing recourse to military measures it certain demands are not accepted. It is noteworthy that the provision has also taken into account the Indirect use of force and as a result is also prohibited under the charter[iv].

Interpretation of Article 2(4):

For the purpose of interpretation of Article 2(4) there are 2 possible school of thoughts:

  1. Permissive view: This view has not imposed a complete ban on use of force by state, as such it has been permitted under some special circumstances such as the:
  2. In anticipation of future attack;
  3. To rescue nationals abroad;
  4. Humanitarian intervention;
  5. Regime change
  6. Restrictive view: This school of view that there is radical change in school of thought relating to use of force by state after coming of charter[v]. It has imposed a complete blanket ban on use of force except in the exceptions listed down in the charter. There are two exceptions permitted under the charter;
  7. Self- Defence under Article 51 of charter;
  8. Enforcement action under chapter VII of the charter.

The established rule after analysis of practices of authorities it is clear that the restrictive law is the established rule of practice in International Law, as only 2 (US and Israel) out of 192 countries do support the permissive school of view. Therefore, in summary the rule is that use of force by state for whatever purpose is banned unless explicitly allowed by the charter of United Nations.

Another important concept to be understood in use of force is the topic of Collective Self Defense as existent in the international arena. The topic of collective self-defence is best understood through the Nicaragua Case.

Nicaragua Case:

Nicaragua Case is considered as a landmark case as it had dealt with several prominent issues such as the:

  1. Principle of non- use of force;
  2. Principle of non- intervention;
  3. Collective self- defense

Facts of Case:

Nicaragua had alleged that the United states was responsible for certain military operations on territory of Nicaragua. It claimed that the United States had used direct armed force against it by laying mines in Nicaraguan waters, and attacking and damaging Nicaraguan ports and oil installations and given assistance to the contras, Nicaraguan guerillas fighting to overthrow the Nicaraguan Government.

Principle of non-use of force:

The facts of the case though show that the arming and training of the contras can certainly be said to involve the threat or use of use of force against Nicaragua, this may not be true in case of assistance provided by the United States. The court considered that though the supply of funds to organization amounts to interference in internal affairs of Nicaragua but it does not amount to use of force.

Principle of non-intervention:

The customary principle of international law has prohibited states or group of states from interfering directly or indirectly in internal or external affairs of another state. The principle of non- intervention is traced back to the doctrine of sovereignty, which allows a state to choose any social, political, economic and cultural system and also to formulate any foreign policy it likes without any other state interfering in its matters.

On Collective self defence:

It is understood that despite the fact that the international law imposes a complete ban on use of force by state, still this rule is not absolute and it is limited by certain exceptions such as the right of self defense as propounded under Article 51 of United Nations Charter. The self defense can be either individual or collective self defense and it is noteworthy that this right is also not absolute and to avail this defense there are certain conditions which needs to be fulfilled as well;

  1. An armed attack by another state; i.e. the concerned state being victim of an armed attack;
  2. Necessity of self- defense;
  3. Proportionality.

It is noted that to avail the benefit of collective self defense there is a condition of a state, i.e. considering itself as victim of armed attack must make a request to the other states. Tus, the condition requiring request to be made by victim state to other states for coming to its assistance is an additional requirement.

Judgment of Court:

  • The world Court ruled in favour of Nicaragua;
  • It held that the United States was under an obligation to make reparation to Nicaragua for injury caused to Nicaragua by breaches of obligation under international law.

Right of Self Defence of States:

Moving on, the topic of self defense has been discussed under Article 51 of United Nations Charter. The article states that nothing in this charter shall affect the inherent right of individual and collective self defense if an armed attack occurs against a member of United Nations, until the Security Council has taken measures necessary to maintain international peace and security. Furthermore, if any action is taken by the individual member in the exercise of this right shall be immediately reported to the Security Council. The article has undertaken to define the word armed attack clearly and ambiguous, but it is subject to the limitation that there must be an armed attack against the state claiming the defense.

Similarly, to the threat to use force or use of force, there are two conflicting school of thoughts for this issue as well. These are as the following:  

  1. Permissive View: It maintains that the right of self defense of state is not merely limited to the situation of armed attacks only and as such states have wider rights in relation to self defense as provided under customary international law.  
  2. Restrictive View: The permissive school is of the view that the right of self defense of states is limited to the situation of actual armed attack against the victim state. It is thus clear that this school has a restricted scope as it restricts the right of self defense to a very limited sense or narrow sense as it has limited it only to the situation of occurring of actual armed conflict. Thus, it is responsible for limiting the freedom of action which states have under the traditional international law.  

In this regard also it is the restrictive view which is considered as the correct view as it is clear that the article 51 by using the words “if an armed attack occurs” has made the scope of the article very clear and unambiguous and thus the textual interpretation shall prevail over the travauxpreparatories and also this article in in conformity with the purpose of the United Nations, i.e. prevention of use of force [Article 2(4)].

Legality of anticipatory self defence: 

The topic of anticipatory self defence is the most widely debated topic of discussion among the experts of the field as it allows the state to have a right to self defence whenever an attack is expected. This idea may be evolved from the idea of “military necessity”, as it is considered that the best defence is to attack first.

It was stated by Bowettthat “no state can be expected to wait an initial attack which, in the present state of armaments, may well destroy state’s capacity for further resistance and so jeopardize its very existence”.

The two major arguments in favor of the legality of anticipatory self defence are as the following:

  1. It is allowed by customary international law;
  2. Also nuclear weapons and modern sophisticated devices has made it unadvisable to wait for future attack.

The Caroline Case[vi] is considered as the landmark precedent case on issue of anticipatory self defence and as such a rule of customary international law has been formed through subsequent state practice.

Caroline Case:

  • The case arose out of Canadian rebellion of 1837. It was concerning an American ship which was used by Canadian rebels to harass British authorities in Canada;
  • The ship when was moored in American Port, a British force from Canada entered upon United states territory, seized the Caroline, fired her and sent her over Niagara Falls;
  • The legality of attack was discussed in great detail in correspondence between Great Britain and United States;

This case was regarded as an instance of practice between two countries but to establish a customary rule of law, it needs support of more than 2 countries while the rule of anticipatory self defense is only accepted and applied by United States and Israel in their usual practice.

Therefore, the anticipatory self defense, as formulated under Caroline Case is not supported by subsequent state practice and cannot be said as forming part of the customary law of the time.

Individual Self Defence:

The right of individual self defense has been accepted as a right developed under customary international law and this right was reaffirmed in the Nicaragua Case and it is subject to the limitations such as the;

  • Necessity;
  • Proportionality


It is without a doubt that the right of self defense is available only in situation of occurring of armed attack against the state. Thus, the requirement of necessity appears to be mainly the requirement for ascertaining whether there is an actual armed attack against the state. It is also necessary to show that the state had no other to halt the attack other than recourse to the actual armed force. It is as so as if the attack can be halted by any other means than use of force, it would have no justification for using armed force in self defense.


It is a general rule of law that the action taken must be in proportion to the danger in terms of the armed attack by another state. The ICJ in Nicaragua Case had stated that the activities of United States, those relating to mining of Nicaraguan ports and attack on ports, oil installations, etc. as satisfying the criterion.

There are 3 main objectives of self- defence and once they are achieved it becomes necessary to end the self defence acts as well. The objectives are as the following[vii]:

  • Fending off current, persistent attacks;
  • Fending off and protection from further attacks, which constitute an integral part of continuum of hostilities;
  • Restoration of territorial status quo ante bellum.

Finally, the most important role in use of force is played by the security Council of United Nations.

Role of Security Council:

The role or responsibility of the Security Council has been discussed under Article 51 of Charter and as such provides for a great role in respect of exercise of self defence. There are 2 principal aspects of the role of Security Council:

  • Measures taken by the states shall be immediately reported to the Security Council; this is known as the “reporting duty of state”;
  • It is also noteworthy that the right of self defence is exercisable only till the point that the Security Council has undertaken measures necessary to maintain international peace and security (It is considered only as a temporary measure).


It is easily understood by now that till the year 1945, i.e. before the establishment of United Nations, there was no law in international arena for the regulation of use of force by states in international relations with one another and rather the states could use force against other states on their own discretion and the only guiding factor was whether the use was justified or unjustified. This all and inability of League of Nations to act successfully resulted in World War-II and as such after it was the United Nations was established in 1945, which in its two articles under Article 2(4) and Article 51 has dealt with the issue in hand which has prohibited use of force and right of self defence respectively. There are also two possible school of thoughts, permissive and restrictive school of view which also have contrasting opinions upon the use of force by states and also the charter has undertaken to clearly specify the conditions under which the defence of self defence can be used in the international arena.  Furthermore, the charter has also specified the role and responsibility of the Security Council with the view to maintain international peace and security and also there is a duty imposed on the states to report action undertaken by them to security council and also report it to the Security Council immediately after taking off the action as well. Thus, it can be concluded that the use of force by states in international relations is prohibited but it can be used to a permissible limit on fulfilment of certain conditions as specified under the International Law.

[i] Article 51 of United Nations Charter


[iii] Article 2(4) of United Nations Charter

[iv] Nicaragua Case: Military and Paramilitary activities in and against Nicaragua (Nicaragua Vs United States); 1986 I.C.J. 14


[vi]Caroline Case: 30 B.F.S.P. 195-196

[vii] Supra

[viii] OUP blog


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