Principle of Neutrality
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This article has been written by Neha Mallik from VIPS, Delhi. This article talks about the legality of the use of nuclear weapons. 


In this nuclear era, many States possess nuclear warheads. With the current dispute between the US and Iran, you have probably heard about nuclear weapons. Nuclear weapons are the most powerful weapons which could destroy the whole city in the blink of an eye. More than 90% of the nuclear warheads belong to the United Nation and Russia. There has been lots of talk about who can have them, use them, manufacture or develop them. It’s very important and interesting for anyone to know about the legality related to the use of such a massive destructive weapon. This article would give you an insight about the legality of the use of weapons and other relevant things which you should know.

Brief Description of the landmark case “Legality of the use of nuclear Weapons”

The World Health Organization was the first to raise the issue regarding the legality of the use of nuclear weapons before the International Court of Justice on 14th May, 1993. WHO asked ICJ to give an advisory opinion on the question “ in the view of the health and environmental effects, would the use of nuclears by a State in war or other armed conflict be a breach of its obligations under international law including the WHO Constitution?” by adopting a resolution. Followed by this, on 15th December, 1994, the United Nation General Assembly, adopted a resolution requesting the ICJ to give advisory opinion questioning “What are the circumstances wherein the use or threat to use the nuclear weapons permitted under international law?” While refusing to address the question from WHO, stating that WHO is not an authorised body to ask this question, ICJ however responded to the request made by the United Nations General Assembly. 

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Determination of applicable laws

In order to address the question relating to the legality of the use of nuclear weapons, it is imperative for the Court to consider the potentially relevant areas of international laws. 

  • Human Rights- According to the fundamental principle of right to life “every human being has the right to life inherently. This right has been protected by every law. According to the provision in International Covenant on Civil and Political Rights (ICCPR)- no one shall be arbitrarily deprived of his right to life. Hence the right to life has to be conferred in war as well as in the peacetime. 
  • Environmental Law- Considering the environmental laws, the Court mentioned two treaties. Firstly, Protocol I, which prohibits the employment of “methods or means of warfare that are intended, or expected to cause widespread and serious damage to the natural environment. Secondly, there is a provision in the Environmental Modification Convention which specifically prohibits the use of weapons creating severe effects to the environment. 

According to the principle of Rio Declaration and Stockholm Declarartion States have a duty to ensure that they would not indulge in any activity causing damage to the environment. Having said that, the duty not to cause transboundary harm is a customary law and secondly to use the nuclear weapons in wartime the States need to evaluate the necessity and proportionality in the military activities. 

The International Court of Justice in its advisory opinion discussed 5 substantive questions

  • Do any treaty or customary law authorize or talk about the use of nuclear weapons?

The Court established that no treaty or customary law explicitly or expressly authorizes the use of nuclear weapons. Considering the principle established in the Lotus Case, “States are free to threaten or use nuclear weapons unless it can be shown that they are bound not to do so”. Furthermore, the Court went to analyse if any treaty or customary law universally prohibits the use of threat in nuclear weapons.

  • Do any treaty or customary law contain absolute prohibition on the use or threat to use nuclear weapons?

The Court turned to the nuclear weapons treaties in order to ascertain whether any treaty makes the threat or use of nuclear weapons per se prohibited or not. Furthermore the Court differentiated the poison weapons with nuclear weapons as the treaties related to poison weapons would not be applicable to nuclear weapons. The Court found out that almost all the nuclear treaties address the acquisition, manufacture, possession or testing of nuclear weapons. Eventually the Court concluded that no treaty contains absolute prohibition on the use or threat to use nuclear weapons. 

In terms of UN Charter, that is considered to be the most relevant law relating to this subject and armed conflict, it also does not expressly prohibit the use of nuclear weapons. According to the provisions under Article 2(4), Article 42, and Article 51 of the UN Charter the legality on the use of force is silent on certain weapons. Moreover other humanitarian law treaties that govern mass destructive weapons also do not contain absolute prohibitions.

Talking about the customary laws mirroring the treaty analysis the Court determined whether any customary international law provides per se prohibition on the use of nuclear weapons? ICJ found out that the State practices and opinio juris relating to the use of nuclear weapons differ from State to State. Since world war II, many States encouraged the non use of nuclear weapons and adopted the cold war policy. As a matter of fact there is no conventional or customary rule per se prohibiting the threat or use of nuclear weapons. 

  • Compatibility with international humanitarian law and other relevant laws 

So far the Court has observed that there is no provision in the International Law that authorizes or per se prohibits the use of nuclear weapons, further the Court examined whether the laws relating to the use of these weapons are consistent with the laws applicable to armed conflicts including International Humanitarian Law and UN Charter.

  • UN Charter- Though the UN charter neither expressly permit nor prohibit the use of nuclear weapons, the same however asserts that for a threat or use of force to be lawful as per Article 51, the use of these weapons shall be proportionate to the armed attack and necessary. 
  • International Humanitarian Law- The Court is in the opinion that even if the use of nuclear weapons is lawfull, still it must comply with the provisions of laws applicable to armed conflicts, humanitarian laws and other relevant laws. 
  • Situations in case of self defense 

Article 51 of the UN Charter states the provision regarding the use of nuclear weapons in pertaining to self defense. There are certain restrictions to the right to self defense:

  • Firstly, for the act considered to be an act of self defence, the use of force must be in self defense only. 
  • Secondly the defending State is required to report the measures taken in order to protect itself to the Security Council of the United Nation. 
  • And last but not the least the measure taken for self defense must be in conformity with the customary international Principles of necessity and proportionality. 

It is argued that proportionality is impossible as the different weapons have unique destructive capabilities. As a matter of fact, the proportionality is analysis considering the factors like destructive capabilities, the heat and energy that would be emitted using the weapons, the radiation that might be released, the potential a weapon has in destroying the ecosystem, the effect it can cause to the environment and other such factors. Concisely, these standards should be kept in mind while exercising the right of self defense. 

  • Promotion of nuclear disarmament

After critical analysis, the Court is in the opinion that the States should continue to have negotiations and agreements towards nuclear disarmament. For environment protection and human welfare, the States are legally to go for such negotiations that bring nuclear disarmament.
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Principle of Neutrality

The principle of neutrality is one of the customary international laws which is very imperative to be considered while talking about the armed conflicts. Neutrality is a formal status given to a State which is not a party to an armed conflict. This principle gives rise to rights & duties to both neutral and belligerent States. The States which are neutral have the right to remain separate from the conflict and to get harmed. The neutral States are protected against the effects of nuclear weapons and are assumed to comply with the duties of impartiality. So again, it is imperative to take the principle of neutrality into consideration while discussing the legality of the use of nuclear weapons.

Environmental Law and Self defence

It is known to everyone that the destructive nuclear weapons create long-lasting damage to the ecosystem. It is indispensable on the part of the State to take environmental considerations into account in order to measure the degree of necessity and proportionality in the pursuit of self defense. So even if the use of nuclear weapons is not illegal one should respect the environment law by complying with it. As in the landmark ICJ opinion, “Legality of the use or threat to use the nuclear weapons, the Court recognized the duty of the State not to cause the transboundary harm and also observed that the environment is one of the important factors that must be considered while evaluating necessity and proportionality limiting the scope of the latter principle. This not only draws balance between the justified use of force in case of self defense but also creates a sense of respect towards the environment. In the opinion of the Court, incorporating environmental concerns into the law of armed conflict is essential. Under this approach, a belligerent State could harm the ecosystem in self defense only to the extent of the harm which is necessary and proportionate to the legitimate military activities especially the use of nuclear weapons. Concluding it, it is must to draw balance between the two important doctrines of self defense and environmental laws.

Ban on the testing of nuclear weapons

The race of nuclear warheads amongst the States has reached a dangerous level. Moreover, there have been a lot of public protests happening against testing of nuclear weapons. The nuclear weapons are tested to carry out experiments to determine the effectiveness and destructive capabilities of the weapons. These are being tested in atmosphere, underground or even underwater. It is evident that nuclear weapons tests have had serious implications on health and the environment, Hiroshima Nagasaki nuclear test being one of the great instances. The discussion concerning the ban on nuclear testing has been going on for a long time. There exists many treaties against the testing on nuclear weapons, Partial Nuclear Test Ban Treaty and Comprehensive Nuclear Test Ban treaty being some of them.The treaty has been signed by more than 180 nations. Although countries like India, North Korea and Pakistan have not ratified it yet. Let’s talk about some treaties briefly.

Nuclear Non-proliferation treaty

The NPT objects to promote nuclear disarmament and to prevent the spread of nuclear technology. It is a landmark International treaty which had been opened for signature in 1968. Currently more the 190 countries have joined the treaty including the 5 nuclear weapon States i.e. US, U.K, France, Russia and China. 

The NPT acts as a cornerstone of the global proliferation regime. The treaty also promotes cooperation in the peaceful uses of nuclear is noted that 2020 is the 50th anniversary of the NPT.

Limited Test Ban Treaty (LTBT)

The Limited Test Ban Treaty, also known as Partial Test Ban Treaty is a treaty which prohibits testing of nuclear weapons in the atmosphere including the outer space and under water. 

Comprehensive Test Ban Treaty (CTBT)

Comprehensive Test Ban Treaty, unlike LTBT, bans nuclear explosions everywhere. With more than 190 signatories the treaty has not entered into force as it needs to be ratified by at least 44 specific nuclear technology holding States as per Article XIV of the treaty. 


Wrapping up, I would like to highlight that despite various steps have been taken to promote complete disarmament, there is no absolute rule which absolutely prohibits the use or threat to use nuclear weapons. Having said that, it is imperative to take strict measures to control the use and test of nuclear weapons so that the environment can be least affected and health hazard due to the radiation of these weapons can be reduced. 


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