Problem 4
Under which conditions does international law allow the
use of force and when are states allowed to use force?
International law distinguishes between rules regulating when and for what purpose a state
may use force against another state (jus ad bellum), and those relating to how military
hostilities must be conducted (jus in bello).
The UN Charter and the prohibition on the use of force
The prohibition on the use of force is contained in article 2(4) of the UN Charter. The concept
of ‘force’ has been limited to armed measures. Not only the use of force directed at
territorial integrity and political independence is prohibited, but all uses of force are
prohibited.
In Nicaragua, the ICJ stated that the use of force is regulated in both the UN Charter and in
customary international law (Par. 174), and that the content of the two sources are not
identical (Par. 181).
Using force on the basis of valid consent from the host state is not prescribed by article 2(4).
Consent is a circumstance that precludes the wrongfulness of an act. A situation when the
use of force is based on consent of the host state is a UN peacekeeping operation.
The legitimacy of consent to the use of force seems to be influenced by the extent to which
the consenting government is seen as representative of the will of the population and/or if
the government has been recognized by the international community and not yet been
replaced by another entity.
Interferences that fall below the threshold for constituting force under
article 2(4)
Sometimes, an interference from a state does not constitute force under article 2(4), but
violates international law.
First, the principle of territorial sovereignty dictates that a state may not exercise its physical
power in any form in the territory of another state. If a state does so, it is considered a
breach of sovereignty. This is reflected in article 2(1) of the Charter. Peacetime espionage
does not violate this law, but the way it is conducted can.
Secondly, an interference that falls below the threshold of force may also violate the
principle of non-intervention, according to which another state cannot interfere in internal
affairs of a different state. This has been stated in Nicaragua as well (Par. 202). Prohibition
against interventions consists of two elements:
1. An intervention (attempt to coerce)
2. Aimed at a matter in which each state is permitted to decide freely
, In Nicaragua, the ICJ found that US supported the military and paramilitary activities of the
Nicaraguan contras, including financial support, training, weapons supply and intelligence
and logistical support, violated the principle of non-intervention (Par. 228).
A state that is victim to a breach of sovereignty or unlawful intervention may initiate
countermeasures against the responsible state. A countermeasure cannot take the form of
use of force unless it is response to an armed attack.
The unilateral use of force by states
The right to self-defense
The use of force in self-defense constitutes an exception to the prohibition of force in article
2(4), and is regulated in article 51 of the Charter.
In the article, it is mentioned that the right of self-defense is an ‘inherent’ right. In Nicaragua
it is stated that the term testifies to the existence of a right to self-defense under customary
international law that exists alongside article 51 (Par. 193 & 176).
An armed attack
The right to self-defense is triggered by an armed attack. To qualify, the attack must be of a
certain intensity and not all uses of force will trigger a right to self-defense.
In Nicaragua, the ICJ distinguishes between the most grave forms of the use of force and
other grave forms (Par. 191). It is also stated that provisions of weapons etc. fall outside the
ambit of article 51 (Par. 195).
Attacks that cause territorial invasions, human fatalities or massive destruction of property
will suffice to constitute an armed attack. In some cases, small-scale attacks that would not
be sufficient to constitute an armed attack will do so when performed in large amounts.
Attacks on objects or individuals located on the territory of a state or on a state’s military
installations and/or military personnel abroad may constitute an armed attack. The same
goes for ambassies.
Attacks by private actors
Private actors can trigger the right to self-defense when a private actor located in another
state commits an attack, and the host state does not have the ability or willingness to stop
the private actor’s activities.
The initiation of self-defense
According to article 51, the right to self-defense is triggered when an armed attack occurs. A
state that fears a potential attack can make military preparations, and bring the situation to
the attention of the Security Council, but cannot take measures.
A state can be entitled to resort to anticipatory self-defense when the threat is imminent.
1. A right to anticipatory self-defense must be interpreted narrowly and only relied on
in exceptional circumstances
Under which conditions does international law allow the
use of force and when are states allowed to use force?
International law distinguishes between rules regulating when and for what purpose a state
may use force against another state (jus ad bellum), and those relating to how military
hostilities must be conducted (jus in bello).
The UN Charter and the prohibition on the use of force
The prohibition on the use of force is contained in article 2(4) of the UN Charter. The concept
of ‘force’ has been limited to armed measures. Not only the use of force directed at
territorial integrity and political independence is prohibited, but all uses of force are
prohibited.
In Nicaragua, the ICJ stated that the use of force is regulated in both the UN Charter and in
customary international law (Par. 174), and that the content of the two sources are not
identical (Par. 181).
Using force on the basis of valid consent from the host state is not prescribed by article 2(4).
Consent is a circumstance that precludes the wrongfulness of an act. A situation when the
use of force is based on consent of the host state is a UN peacekeeping operation.
The legitimacy of consent to the use of force seems to be influenced by the extent to which
the consenting government is seen as representative of the will of the population and/or if
the government has been recognized by the international community and not yet been
replaced by another entity.
Interferences that fall below the threshold for constituting force under
article 2(4)
Sometimes, an interference from a state does not constitute force under article 2(4), but
violates international law.
First, the principle of territorial sovereignty dictates that a state may not exercise its physical
power in any form in the territory of another state. If a state does so, it is considered a
breach of sovereignty. This is reflected in article 2(1) of the Charter. Peacetime espionage
does not violate this law, but the way it is conducted can.
Secondly, an interference that falls below the threshold of force may also violate the
principle of non-intervention, according to which another state cannot interfere in internal
affairs of a different state. This has been stated in Nicaragua as well (Par. 202). Prohibition
against interventions consists of two elements:
1. An intervention (attempt to coerce)
2. Aimed at a matter in which each state is permitted to decide freely
, In Nicaragua, the ICJ found that US supported the military and paramilitary activities of the
Nicaraguan contras, including financial support, training, weapons supply and intelligence
and logistical support, violated the principle of non-intervention (Par. 228).
A state that is victim to a breach of sovereignty or unlawful intervention may initiate
countermeasures against the responsible state. A countermeasure cannot take the form of
use of force unless it is response to an armed attack.
The unilateral use of force by states
The right to self-defense
The use of force in self-defense constitutes an exception to the prohibition of force in article
2(4), and is regulated in article 51 of the Charter.
In the article, it is mentioned that the right of self-defense is an ‘inherent’ right. In Nicaragua
it is stated that the term testifies to the existence of a right to self-defense under customary
international law that exists alongside article 51 (Par. 193 & 176).
An armed attack
The right to self-defense is triggered by an armed attack. To qualify, the attack must be of a
certain intensity and not all uses of force will trigger a right to self-defense.
In Nicaragua, the ICJ distinguishes between the most grave forms of the use of force and
other grave forms (Par. 191). It is also stated that provisions of weapons etc. fall outside the
ambit of article 51 (Par. 195).
Attacks that cause territorial invasions, human fatalities or massive destruction of property
will suffice to constitute an armed attack. In some cases, small-scale attacks that would not
be sufficient to constitute an armed attack will do so when performed in large amounts.
Attacks on objects or individuals located on the territory of a state or on a state’s military
installations and/or military personnel abroad may constitute an armed attack. The same
goes for ambassies.
Attacks by private actors
Private actors can trigger the right to self-defense when a private actor located in another
state commits an attack, and the host state does not have the ability or willingness to stop
the private actor’s activities.
The initiation of self-defense
According to article 51, the right to self-defense is triggered when an armed attack occurs. A
state that fears a potential attack can make military preparations, and bring the situation to
the attention of the Security Council, but cannot take measures.
A state can be entitled to resort to anticipatory self-defense when the threat is imminent.
1. A right to anticipatory self-defense must be interpreted narrowly and only relied on
in exceptional circumstances
