Use of Force in International Law (JUFN27)
Autumn semester, 2015
Seminar No. 2
• Advisory opinion of the International Court of Justice in Legality of the Threat or Use of
Nuclear Weapons, Seminar Materials, pp. 47-73.
According to the International Court of Justice, a use of nuclear weapons shall be considered
legal, unless states are not prohibited from using such weapons by a rule of international law;
the same principle applies to the threat of the use of nuclear weapons. The following
arguments have been put forth to support the claim that there does indeed exist in
international law a prohibition against threat or use of nuclear weapons:

If a state uses nuclear weapons, this constitutes a violation of the right to life laid down in
Article 6 of the International Covenant on Civil and Political Rights. (§§ 24-25)

If a state uses nuclear weapons, this constitutes a violation of the prohibition in
international law on genocide.

If a state uses nuclear weapons, this constitutes a violation of the existing international law
on the protection of the environment.

If a state uses or threatens to use nuclear weapons, this is a violation of the jus ad bellum
laid down in Article 2 paragraph 4 and Article 51 of the UN Charter.

A general and absolute prohibition against the use of nuclear weapons is laid down in a
number of international treaties.

A general and absolute prohibition against the use of nuclear weapons exists in customary
international law.

If a state uses nuclear weapons, this constitutes a violation of rules found in both
international humanitarian law (IHL) and the law of neutrality.
In this Seminar, we will concentrate on the aspects of the argument which concern the
relationship between IHL/neutrality law and general international law, and the jus ad bellum
in particular. Seminar Groups 1 and 3 have primary responsibility for the task and shall
discuss the cases together with Groups 2 and 4, respectively.
(1) Several states assert that the use of nuclear weapons violates the right to life laid down in
the International Covenant on Civil and Political Rights (ICCPR). According to Article 6
paragraph 1 of the Covenant, “[n]o one shall be arbitrarily deprived of his life”. In principle,
as reaffirmed by the Court, this right must be respected, even in armed conflict. However, the
Court is quick to add:
The test of what is an arbitrary deprivation of life, however, then falls to be determined by the applicable lex
specialis, namely, the law applicable in armed conflict which is designed to regulate the conduct of
hostilities. Thus whether a particular loss of life, through the use of a certain weapon in warfare, is to be
considered an arbitrary deprivation of life contrary to Article 6 of the Covenant, can only be decided by
reference to the law applicable in armed conflict and not deduced from the terms of the Covenant itself.
What is the proposition actually expressed by this statement? The statement can be interpreted
differently. According to a first alternative, Article 6 paragraph 1 shall be interpreted in the
light of IHL, which, so to speak, thus gives meaning to the expression “arbitrarily”.
According to a second alternative, as soon as an armed conflict is at hand, the meaning of the
right to life will depend, not on Article 6 paragraph 1 of the ICCPR, but on IHL, since in
situations of armed conflict IHL takes priority over ICCPR Article 6 § 1. Which of the two
alternatives would you regard as correct? What difference does it make whether we choose to
regard the relationship between the ICCPR and IHL according to the one or the other
alternative?
(2) One interesting question raised by the Court’s opinion is the matter of the relationship
between the right of self-defence and IHL. An exercise of the right of self-defence is always
subject to the principle of proportionality: In order for a self-defence measure to be
considered legal, it must be proportionate. The Court confirms this proposition, but then adds:
“[A] use of force that is proportionate under the law of self-defence, must, in order to be
lawful, also meet the requirements of the law applicable in armed conflict which comprises in
particular the principles and rules of humanitarian law” (para. 42). Commentators have
pondered over the meaning and significance of this statement. It would seem that in the view
of the Court, it is a requirement following from the right of self-defence that the use of
nuclear weapons must be consistent with IHL and neutrality law. In other words: whether or
not a particular use by a state of nuclear weapons is consistent with Article 51 of the UN
Charter (or the corresponding rule of customary international law) will depend partly on
whether that use is consistent with IHL and neutrality law. What are the further implications
of this line of reasoning?
(3) As held by the Court, there is in customary international law no general, absolute
prohibition against the use by states of nuclear weapons. We can ask ourselves if this absence
of a general prohibition really makes any difference. Could one expect it to lie in the very
nature of nuclear weapons that their use will always conflict with IHL and neutrality law,
irrespective of the particular circumstances that may prevail in each and every single
instance? The Court does not fully accept this assumption. Would you please explain the
Court’s reasoning in this regard!
(4) Thus, the International Court of Justice does not exclude the possibility that in some
particular situations a use of nuclear weapons could be consistent with IHL and neutrality law.
In addition, the Court seems to have left nuclear states an opportunity to subordinate IHL and
neutrality law to Article 51 of the UN Charter: “[T]he Court cannot lose sight of the
fundamental right of every State to survival, and thus its right to resort to self-defence, in
accordance with Article 51 of the Charter, when its survival is at stake.” What does this mean
exactly? Can the proposition expressed by the Court be reconciled with its earlier statement
concerning the relationship between IHL/neutrality law and the right of self-defence? (See
para. 423.) Can it be reconciled with the description given of the right of self-defence in
Article 21 of the ARSIWA?