ASIL Insights

On July 8, 1996, the International Court of Justice (ICJ), popularly known as the World Court, delivered two advisory opinions on separate requests received from the World Health Organization and the General Assembly of the United Nations, respectively, relating to the legality of nuclear weapons under international law. The principal judicial organ of the United Nations, whose Statute forms an integral part of the UN Charter, consists of 15 judges representing the different regions and principal legal systems of the world. In addition to the Court's function of delivering judgments in contentions cases submitted to it by states, it may issue non-binding advisory opinions at the request of certain UN organs and agencies.
 

Legality of the Threat or Use of Nuclear Weapons
 

On December 20, 1994, the UN General Assembly requested the ICJ to give an advisory opinion on the question: "Is the threat or use of nuclear weapons in any circumstance permitted under international law?"
 

At the outset, the ICJ confirmed the Assembly's broad competence to make such a request, deriving from the UN Charter and the Assembly's longstanding activities regarding disarmament and nuclear weapons. The Court also found that the request related to a legal question within the meaning of the ICJ Statute and the UN Charter and that there were no compelling reasons to refuse the request, even though the question put to it did not relate to a specific dispute and was couched in abstract terms.
 

In determining the legality or illegality of the threat or external use of nuclear weapons, the ICJ decided that the most directly relevant applicable law governing the Assembly's question consisted of (1) the provisions of the UN Charter relating to the threat or use of force, (2) the principles and rules of international humanitarian law that form part of the law applicable in armed conflict and the law of neutrality, and (3) any relevant specific treaties on nuclear weapons. In applying this law, the Court considered it imperative to take into account certain unique characteristics of nuclear weapons, in particular their destructive capacity that can cause untold human suffering for generations to come.
 

The Court first considered the provisions of the UN Charter relating to the threat or use of force. Although Article 2(4) (generally prohibiting the threat or use of force), Article 51 (recognizing every state's inherent right of individual or collective self-defense if an armed attack occurs) and Article 42 (authorizing the Security Council to take military enforcement measures) do not refer to specific weapons, the Court held that they apply to any use of force, regardless of the type of weapon employed. The Court noted that the UN Charter neither expressly prohibits, nor permits, the use of any specific weapon (including nuclear weapons) and that a weapon that is already unlawful per se by treaty or custom does not become lawful by reason of its being used for a legitimate purpose under the Charter. Whatever the means of force used in self-defense, the dual customary condition of necessity and proportionality and the law applicable in armed conflict apply, including such further considerations as the very nature of nuclear weapons and the profound risks associated with their use.
 

The ICJ also considered the question whether a signalled intention to use force if certain events occur qualifies as an unlawful "threat" under Article 2(4) of the UN Charter. According to the Court, the notions of "threat" or "use" of force under Article 2(4) work in tandem in that the illegal use of force in a given case will likewise make the threat to use such force unlawful. The Court pointed out that the mere possession of nuclear weapons would not constitute an unlawful "threat" to use force contrary to Article 2(4), unless the particular use of force envisaged would be directed against the territorial integrity or political independence of a state or would be inconsistent with the purposes of the United Nations or, in the event that it were intended as a means of defense, such envisaged use of force would violate the principles of necessity and proportionality.
 

The Court next examined the law applicable in situations of armed conflict by addressing two questions: (1) are there specific rules in international law regulating the legality or illegality of recourse to nuclear weapons per se, and (2) what are the implications of the principles and rules of humanitarian law applicable in armed conflict and the law of neutrality?
 

The ICJ noted that international customary and treaty law do not contain any specific prescription authorizing the threat or use of nuclear weapons or any other weapon in general or in certain circumstances, in particular those of the exercise of legitimate self-defense. Nor, however, is there any principle or rule of international law that would make the legality of the threat or use of nuclear weapons or of any other weapons dependent on a specific authorization. State practice shows that the illegality of the use of certain weapons as such does not result from an absence of authorization but is rather formulated in terms of prohibition.
 

The Court examined whether any such prohibition of recourse to nuclear weapons can be found in treaty law. With regard to certain specific treaties dealing with the acquisition, manufacture, possession, deployment and testing of nuclear weapons, the Court noted that these treaties "point to an increasing concern in the international community" with regard to nuclear weapons, and concluded that they "could therefore be seen as foreshadowing a future general prohibition of the use of such weapons, but they do not constitute such a prohibition by themselves." As to those treaties that address the issue of recourse to nuclear weapons, the Court observed that they "testify to a growing awareness of the need to liberate the community of States and the international public from the dangers resulting from the existence of nuclear weapons," but that these treaties also do not amount to a comprehensive and universal conventional prohibition on the threat or use of nuclear weapons as such.
 

The Court then examined customary international law. First, it determined that the non-use of nuclear weapons does not amount to a customary prohibition, because the world community is profoundly divided on the issue. Second, the Court examined whether certain General Assembly resolutions that deal with nuclear weapons signify the existence of a rule of customary international law prohibiting recourse to nuclear weapons. In the Court's view, although these resolutions are "a clear sign of deep concern regarding the problem of nuclear weapons" and "reveal the desire of a very large section of the international community to take, by a specific and express prohibition of the use of nuclear weapons, a significant step forward along the road to complete nuclear disarmament," they fall short of a customary rule specifically prohibiting the use of nuclear weapons as such.
 

The ICJ next considered whether recourse to nuclear weapons must be considered as illegal in the light of the principles and rules of international humanitarian law applicable in armed conflict and of the law of neutrality. The Court stated that the cardinal principles of international humanitarian law prescribing the conduct of military operations are: (1) the protection of the civilian population and civilian objects and the prohibition of the use of weapons incapable of distinguishing between combatants and non-combatants, and (2) the prohibition on causing unnecessary suffering to combatants by using certain weapons. According to the Court, the fundamental rules of humanitarian law applicable in armed conflict must be observed by all states whether or not they have ratified the conventions that contain them, because they constitute intransgressible principles of international customary law. The ICJ agreed with the vast majority of states as well as writers that there can be no doubt as to the applicability of the principles and rules of humanitarian law in armed conflict to a possible threat or use of nuclear weapons, despite the fact that these principles and rules had evolved prior to the invention of nuclear weapons. It also found that the customary principle of neutrality is applicable, subject to the relevant provisions of the UN Charter, to all international armed conflict, whatever type of weapons might be used (although the principle of neutrality is not well defined, and the ICJ left its content undefined here, it is generally regarded as requiring at least that no attack be made on a state that has declared itself a neutral and is conducting itself accordingly).
 

Despite the undisputed applicability of the principles and rules of humanitarian law and of the law of neutrality to nuclear weapons, the ICJ found that the conclusions to be drawn from this applicability were controversial. The Court admitted that, in view of the unique characteristics of nuclear weapons, their use "in fact seems scarcely reconcilable" with the strict requirements dictated by the law applicable in armed conflict. The judges being evenly divided, ICJ President Mohammed Bedjaoui used his casting vote to hold that the threat or use of nuclear weapons would generally be contrary to the rules of international law applicable in armed conflict. At the same time, the ICJ held that it did not have a sufficient basis for a definitive conclusion as to whether the use of nuclear weapons would or would not be at variance with the principles and rules of law applicable in armed conflict in an extreme circumstance of self-defense, in which a state's very survival is at stake.
 

Finally, the Court examined the obligation to negotiate in good faith a complete nuclear disarmament, recognized in Article VI of the Treaty on the Non-Proliferation of Nuclear Weapons of 1968. The ICJ judges held unanimously that the obligation enshrined in Article VI involves "an obligation to achieve a precise result-nuclear disarmament in all its aspects-by adopting a particular course of conduct, namely, the pursuit of negotiations on the matter in good faith." The Court noted that this twofold obligation to pursue and conclude negotiations in accordance with the basic principle of good faith formally concerns the 182 states parties to the Treaty on the Non-Proliferation of Nuclear Weapons, constituting the vast majority of the international community.
 

Legality of the Use by a State of Nuclear Weapons in Armed Conflict
 

On July 8, 1996, the ICJ ruled also that it was unable to comply with a request received on September 1993 from the World Health Organization (WHO) to give an advisory opinion on the following question: "In view of the health and environmental effects, would the use of nuclear weapons by a State in war or other armed conflict be a breach of its obligations under international law including the WHO Constitution?" The Court ruled, 11-3, that although the WHO is duly authorized under the UN Charter to request advisory opinions from the ICJ and the opinion requested concerned a legal question, the request submitted by the WHO did not relate to a question arising within the scope of the activities of that organization as required by Article 96(2) of the UN Charter.
 

The Court pointed out that its jurisdiction to provide an advisory opinion in response to a request by a specialized agency requires that: (1) the specialized agency requesting the opinion must be duly authorized, under the UN Charter, to request advisory opinions from the ICJ, (2) the opinion requested must relate to a "legal question" within the meaning of the ICJ Statute and the UN Charter, and (3) the opinion requested must relate to a question that arises within the scope of the activities of the specialized agency requesting the opinion.
 

Regarding the third condition, the Court emphasized the importance of the relevant rules, and in particular the constituent instrument, of the WHO in determining the scope of its activities against the background of the question it posed. In interpreting the constituent instrument of an international organization, the character of which is conventional and at the same time institutional (being a treaty establishing an international organization), the Court observed that the following elements deserve special attention: (i) the nature of the international organization, (ii) the objectives assigned to the organization by its founders, (iii) the imperatives associated with the effective performance of the functions of the organization, and (iv) the organization's own practice.
 

The ICJ observed that none of the 22 functions listed in the WHO Constitution expressly refers to the legality of any activity hazardous to health, or depends upon the legality of the situations in which that organization must act. Article 2 states that the WHO discharges its functions "to achieve its objective," which Article 1 defines as "the attainment by all peoples of the highest possible level of health." According to the Court, the functions listed in Article 2 authorize the WHO to deal with the effects on health of the use of nuclear weapons, or any other hazardous activity, and to take preventive measures that are aimed at protecting the health of populations in the event of such weapons being used or such activities engaged in.
 

Having found the request to relate not to the effects of the use of nuclear weapons on health, but rather the legality of the use of such weapons in view of their health and environmental effects, the Court concluded that there was insufficient connection between the request and the functions of the WHO to support the Court's jurisdiction. According to the ICJ: "the legality or illegality of the use of nuclear weapons in no way determines the specific measures, regarding health or otherwise (studies, plans, procedures, etc.), which could be necessary in order to prevent or cure some of their effects."
 

The Court acknowledged that international organizations can exercise subsidiary or "implied" powers not expressly provided for in the basic instruments that govern their activities. However, it held that the competence to address the legality of the use of nuclear weapons could not be deemed a necessary implication of the WHO Constitution in the light of the purposes member states had assigned to it. To hold otherwise would be tantamount to disregarding the principle of speciality according to which international organizations operate in limited fields.
 

The ICJ explained that the logic of the UN Charter system demonstrates that the United Nations was invested with powers of general scope and that specialized agencies such as the WHO were invested with sectorial powers. The responsibilities of the WHO are necessarily restricted to the sphere of public health, and cannot encroach on the responsibilities of other parts of the UN system. More specifically, questions concerning the use of force, the regulation of armaments, and disarmament are within the competence of the United Nations and outside that of the specialized agencies.
 

Finally, the Court pointed out that none of the WHO's reports and resolutions was in the nature of a practice of the WHO concerning the legality of the threat or use of nuclear weapons. It held that in general the WHO is not empowered to seek an opinion on the interpretation of its Constitution in relation to matters outside the scope of its functions.

These advisory opinions of the World Court are of considerable significance to the development of the law of nuclear weapons and international organizations. Although the Court concluded that it was unable to hold definitively whether the threat or use of nuclear weapons would be lawful or unlawful in an extreme circumstance of self-defense in which the very survival of a state would be at stake (thereby leaving the door to legality open) and it could not give the opinion requested by the WHO, the legal reasoning leading to these conclusions reflects the Court's authoritative views on important issues of international law. Although the opinions are non-binding, in preparing them the Court follows the same rules and procedures that govern its binding judgments delivered in contentious cases submitted to it by sovereign states.
 

Further Reading 

Ian Brownlie, Some Legal Aspects of the Use of Nuclear Weapons, 14 ICLQ 437 (1965). 
David M. Corwin, The Legality of Nuclear Arms under International Law, 5 Dickinson JIL 271 (1986). 
Richard Falk, Lee Meyrowitz & Jack Sanderson, Nuclear Weapons and International Law, 20 Ind JIL 541 (1980). 
William R. Hearn, The International Legal Regime Regulating Nuclear Deterrence and Warfare, 61 B.Y.B.I.L. 199 (1981). 
Frits Kalshoven, Arms, Armaments and International Law, 191 RdC 183 (1985 II). 
Elliott L. Meyrowitz, Prohibition of Nuclear Weapons: The Relevance of International Law (1990). 
Elliott L. Meyrowitz, The Opinions of Legal Scholars on the Legal Status of Nuclear Weapons, 24 Stanford JIL 111 (1987). 
Istvan Pogany, ed., Nuclear Weapons and International Law (1987). 
Alfred P. Rubin, Nuclear Weapons and International Law, 8 Fletcher Forum 45 (1984). 
Nagendra Singh & Edward McWhinney, Nuclear Weapons and Contemporary International Law (2nd Rev.Ed. 1989). 
Burns H. Weston, Nuclear Weapons Versus International Law: A Contextual Reassessment, 28 McGill LJ 543 (1982). 

The purpose of ASIL Insights is to provide concise and informed background for developments of interest to the international community. The American Society of  International Law does not take positions on substantive issues, including the ones discussed  in this Insight.