Legality of use of nuclear weapons in the International Law

By: Riddhi Shah, SVKM’s Pravin Gandhi College of Law, Mumbai University

An unprecedented use of nuclear weapons in the world history of mankind occurred on August 6, 1945, during World War II. America dropped the B-29 atomic bomb over Japanese city Hiroshima, leading to the immediate death of 80,000 people and tens of thousands of people died later due to radiation exposure and after-effects of bomb explosion. The Entire world was shaken. Even before the world thought it was over, three days later another atomic bomb was dropped on Nagasaki, killing an estimated 40,000 people. Thus, it marked an era of weapons of mass destruction.[1]Even after so many decades the tremors of bombing were still felt in these two cities; cases related to cancer and other birth defects are still found in human beings due to the terrible ill effects of the nuclear radiation.[2] These two incidents are the best examples of how usage of nuclear weapons can lead to catastrophic humanitarian destruction which one cannot even imagine and since then there has been a great debate about the legality of the use of nuclear weapons and its uses a deterrent mechanism.

Which raises the question whether the use of nuclear weapons violates international law jus ad bellum and jus in bello, international criminal law, and environmental law?

Relevance of use of nuclear weapons under International Law

Any future use of nuclear weapons, if occurs, is likely to be in the conduct of hostilities, and would be judged under the applicable international laws, jus ad bellum and jus in bello.Jus ad bellum refers to the conditions under which States may resort to war or to the use of armed force in general[3].Jus in bello regulates the conduct of parties engaged in an armed conflict[4]. International Humanitarian Law (IHL) is synonymous with jus in bello; it seeks to minimize suffering in armed conflicts, notably by protecting and assisting all victims of armed conflict to the greatest extent possible.

The primary rule under IHL, the “rule of distinction” states that any weapon of a nature to strike military objectives and civilians or civilian objects without distinction is considered unlawful.[5]So, if nuclear weapons are used this principle is inevitable. The rule of distinction is also a norm under customary international law applicable to international armed conflict as well as non-international armed conflict. And as per it the bombing of Hiroshima and Nagasaki would be ruled out.

Supporting the primary rule is the rule of “proportionality” which states that launching an attack which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated, is prohibited.[6]Therefore, it is difficult to use nuclear weapons without causing collateral damage to the civilians and civilian objects. However, that doesn’t mean its use is unlawful as pointed out by Judge Stephen Schwebel in his separate opinion in ICJ’s 1996 advisory opinion.[7]In that, Judge Stephen Schwebel speculated different scenarios where nuclear weapons can be used[8].In his opinion it might be used against submarines as that might not ensue any civilian casualties. Another scenario is its usage in desert. Further, in his opinion, he concluded that in “certain circumstances, such a use of nuclear weapons might meet the tests of discrimination and proportionality; in others not.”

But if the use of nuclear weapons by states were to occur against armed forces of another state then the criteria of jus ad bellum also need to be satisfied. As stated earlier this body of law regulates the interstate use of force and allows the use of weapons including nuclear weapons for self-defence in an armed attack. ICJ in  its Advisory Opinion  in the nuclear weapons case pointed out that, ‘in view of the current state of international law, and of the elements of fact at its disposal, the Court cannot conclude definitively whether use of nuclear weapons would be lawful or unlawful in an extreme circumstance of self-defence, in which the very survival of a State would be at stake.’

The Court, therefore, appeared to leave open the vexing question of whether the legitimacy of an ad bellum cause may justify the use of nuclear weapons in violation of jus in bello.[9]In practice as well as in legal terms, IHL would disintegrate as a result of linking its application to the perceived lawfulness of the ad bellum use of force. Combining the two to the proportionality principles transforms it from a principle of limitation to one that justifies the degree of injury which otherwise would be excessive under jus in bello.

Another general rule of IHL, namely the use of means and methods of warfare which are of a nature to cause superfluous injury or unnecessary suffering is pertinent to note in this context[10]. As the use of nuclear weapons would aggravate the suffering of disabled men and may even lead to their death it would be contrary to the laws of humanity. Therefore, the use of nuclear weapons can only be permitted if all the rules of IHL are followed.

Keeping in mind that the use of nuclear weapons could lead to violations of IHL, and then the state which uses nuclear weapons could also be held liable under International Criminal law (ICL). The 1998 Rome Statute of the International Criminal Court (ICC) can be applied under certain conditions. For instance, in accordance to the provisions of article 6, 7 and 8 of the Rome Statute the use of nuclear weapons under certain circumstances would lead to genocide, crimes against humanity and war crimes. Though there is no explicit jurisdiction with regard to the use of nuclear weapons but it hardly deters from categorizing it as an international crime under ICL.

Another concern of the use of nuclear weapon is the protection of the environment. Before the use of nuclear weapons in hostilities the other things that presuppose are their production, testing, stockpiling, transportation, and deployment. Today only 9 states possess nuclear weapons i.e.5P’s of UNSC (China, France, Russia, the United Kingdom and the United States) and India, Pakistan, Israel and Democratic People’s Republic of Korea (DPK). The 5 P’s of UNSC are covered under the Non-Proliferation of Nuclear Weapons Treaty(NPT) whereas remaining 4, are not de jure under the NPT.[11] India, Pakistan and Israel have refused to sign the treaty while DPK had signed NPT in 1985 as a non-nuclear-weapon state but declared its withdrawal from the treaty on January 10, 2003.

As a result, these 9 states are currently not under NPT’s comprehensive prohibition of NNWS producing or otherwise acquiring nuclear weapons. Though these states are not bound by the treaties that prohibit the production, testing, stockpiling, transportation, and deployment it doesn’t mean that they could not be held under environmental laws involving the activities of nuclear weapons.

Especially when all stages of the nuclear weapon life cycle may cause environmental pollution right from the radioactive substance to chemicals involved in their production and maintenance. It is argued that the states from whose territory the nuclear weapon pollution originated can be held responsible for the harm caused in the affected environment sphere (atmosphere, hydrosphere, lithosphere, biosphere) protected by the respective treaties. Accordingly, they will be subjected to the environmental litigation for non-compliance with their international environmental obligations. International Customary International Law (ICL) now includes a ban on atmospheric testing of the nuclear weapons but the same cannot be said with regard to underground testing. The 1959 Antarctic Treaty prohibits any activity involving nuclear weapons, and prohibits the testing, stockpiling, deployment or launching in or from Antarctica is prohibited.[12]

Under Article 2 of the UN Charter, sovereign states have an obligation to refrain from the threat or use of force against the territorial integrity or political independence of any state. Although the legality of the use of nuclear weapons is hotly contested but can nuclear deterrence be used as a self-defence mechanism? As Article 51 of the UN Charter states that the nothing in the Charter shall impair the inherent right of Nation States self-defence if an armed attack occurs.[13]The concept of nuclear deterrence is based on the premise that possession of nuclear weapons is the ultimate bargain tool in self-defence in the international anarchical system marked by the absence of common supreme authority.[14]So, can it be used as a self-defence mechanism to protect the integrity and national interest of each and every nation state irrespective of size in terms of territory or wealth in terms of resources?


[1]History.Com Editors, Bombing of Hiroshima and Nagasaki, (Nov. 18, 2009) Available at:

[2] ICAN, Hiroshima and Nagasaki Bombings Available at:,chronic%20disease%20among%20the%20survivors.

[3] International Committee of the Red Cross (ICRC), What are jus ad bellum and jus in bello? (Jan. 22, 2015) Available at:

[4] Ibid

[5]  International Committee of the Red Cross (ICRC) Study of Customary IHL, Rule 71, Available at:

[6] Ibid

[7]Case concerning theLegality of the threat or use of nuclear weapons, I. C.J. Reports 1996, p. 226

[8]Stephen M. Schwebel, dissenting opinion in “Legality of the Threat or Use of Nuclear Weapons,” July 8, 1996, p. 98, Available at:

[9] Gro Nystuen, Annie Golden Bersagel and Stuart Casey-Maslen, Nuclear Weapons Under International Law: An Overview, (October, 2014) Available at:

[10] International Committee of the Red Cross (ICRC) Study of Customary IHL, Rule 70, Available at:

[11] Treaty on the Non-Proliferation of Nuclear Weapons, Encyclopaedia Britannica Publisher: Encyclopaedia Britannica, Inc., (Jun 24 2020) Available at:

[12] The Antarctic Treaty 1959, Art. 1 & Art. V, Available at:

[13] Article 51 of UN Charter states that Nothing in the present Charter shall impair the inherent right of individual or collective self-defense if an armed attack occurs against a Member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security. Measures taken by Members in the exercise of this right of self-defense shall be immediately reported to the Security Council and shall not in any way affect the authority and responsibility of the Security Council under the present Charter to take at any time such action as it deems necessary in order to maintain or restore international peace and security.

[14], Nuclear deterrence, Available at:,deterrence%20aims%20to%20prevent%20war.&text=The%20concept%20of%20nuclear%20deterrence,threatening%20their%20vital%20security%20interests.

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