To Use or Not To Use Nuclear Weapons: A Question of Legality

by Jeff Collins

…the use of nuclear weapons is prohibited not because they are or they are [not] called nuclear weapons. They fall under the prohibition of the fundamental and mandatory rules of humanitarian law (which long predates them) by their effects, not because they are nuclear weapons but because they are indiscriminate weapons of mass destruction.”    – Judge Ali-Saab[i]

When it comes to war and armed conflict, international law has always sought to balance military necessity with humanitarian considerations.[ii] It has done so by constraining state behaviour through “regulating the conduct of belligerents and…limiting the weapons that may be used…”[iii] Since 1945, a major challenge to this balancing process has been the threat of nuclear weapons. As the destruction evidenced in Hiroshima and Nagasaki demonstrate, in a world of proliferation (horizontal and vertical) and international terrorism, the international security implications stemming from the existence and use of such weapons is potentially catastrophic.[iv] Unfortunately – from an international legal point of view – the politics of Cold War deterrence prevented the emergence of a specific treaty prohibiting the use of nuclear weapons following World War Two.[v] This, despite the emergence of treaties prohibiting the use of ‘less’ destructive armaments (e.g. landmines) and other ‘weapons of mass destruction’ (e.g. the Chemical Weapons Convention) during the same time period (1945-present).

Therefore, in the absence of a specific treaty prohibiting nuclear weapons, lawyers must resort to basing their arguments “on [the] principles of customary international law”.[vi] These principles are often referred to as the laws of armed conflict, or international humanitarian law (IHL), and when applied to nuclear weapons it becomes quite clear that the use of such a weapon would be illegal. As such, in making the argument that the use of a nuclear weapon is illegal in IHL this paper will: 1) provide a brief overview of IHL and the relevant principles that have emerged over the past two centuries; 2) establish the link between these principles and nuclear weapons; 3) and lastly, describe how the use of nuclear weapons would be a violation of international humanitarian law.[vii]

Firstly, international law as it relates to warfare exists in two broad categories: jus ad bellum and jus in bello.[viii] Jus ad bellum, which is not being examined in this paper, focuses on the justifications states rely on in order to wage war. Jus in bello, another term for IHL, however, is the law of war that “governs the conduct of hostilities in armed conflicts…”[ix] Furthermore, jus in bello is itself subdivided into two categories: ‘Hague law’ and ‘Geneva law’. The term Hague law is in reference to the Hague Conventions of 1899, 1907 and the Additional Protocols I of 1977.[x] Essentially, Hague law is the branch of IHL that sets limits on the means and methods of warfare which may legitimately be used in armed conflict (e.g. prohibiting certain types of weapons).[xi] Geneva law is in reference to the four Geneva Conventions of 1949 and is focused on protecting the “victims of armed conflict and to ameliorate their conditions”.[xii] At one level, this subdivision of IHL is rather artificial as “both sets of norms rest ultimately upon a fundamental principle of proscription concerning the infliction of militarily ‘unnecessary suffering’”.[xiii] However, given the importance of customary international law in contributing to the development of the principles and rules underpinning IHL a brief overview is required before proceeding onto further analysis.

The whole of international law can be divided into two types: customary law and treaty law. The principles derived from customary international law come from state practice (what the majority of states do) and opinion juris (what states say). Customary law, in the case of IHL, includes all “the rules and principles that regulate the conduct of warfare”.[xiv] Customary law is seen as running in parallel to treaty law unless an international treaty includes an article that strictly overrides a principal of customary law. In the case of IHL, none of the treaties discussed above override any of the customary principles. Instead, each treaty expands and codifies the principles as they are. IHL is now regarded by many scholars as having achieved the status of jus cogens and, as such, can now be considered to be permanently binding on every state.

When examining the evolution of IHL there is one thing worth remembering: IHL has “consistently evolved in response to changes in man’s military capabilities with a view toward limiting human suffering and restraining wanton destruction”.[xv] As such, the customary legal roots of humanitarian law go as far back as 1646 when Hugo Grotius made an attempt to codify the “laws of war and peace for an international community that was evolving with ever increasing complexity”.[xvi] By the 1860s the application of the latest advanced weaponry on the battlefield had produced such horrendous results that a number of states came together to issue what is now regarded as “the first international agreement codifying a prohibition on the use of a specific weapon in armed conflict”, the St. Petersburg Declaration.[xvii] Issued in 1868, as a response to the invention of the exploding bullet, the Declaration proclaimed that certain humanitarian principles apply to warfare, specifically that “the right of a nation-state to injure a belligerent is not unlimited.”[xviii]  This statement led to the “adoption of more general principles which have had a lasting effect upon the development of the laws of war”[xix], chief of which is the principle that a state cannot use a weapon that “that would uselessly aggravate the suffering of disabled men or render their deaths inevitable”.[xx] These principles of limiting state conduct in war and prohibiting unnecessary suffering were eventually incorporated into Articles 22 and 23(e) of the 1907 Hague Convention and remain binding on all states to this day.[xxi]

The next major step in the evolution of IHL was the Hague Convention of 1907. This treaty, written in light of the carnage of the Boer and Russo-Japanese wars, was the first major multilateral approach to “codifying the laws of war”.[xxii] The relevant contributions of this treaty to IHL are found in Article 25 which prohibits “the bombing of undefended cities”; Article 27 – which ensures the protection of “buildings devoted to cultural and medical purposes”, and Articles 22 and 23(e) (discussed above).[xxiii] Unfortunately, during World War Two both Axis and Allied states invoked arguments of ‘military necessity’ in order to forego restraint in their pursuance (with the exception of chemical weapons) of ‘strategic bombing’ policies against civilian populations (e.g. Dresden, Tokyo, Coventry, Nagasaki).[xxiv] In the aftermath of that war another push was made to codify and expand IHL, this time with the view of protecting certain classes of people from unnecessary suffering.

The 1949 Geneva Conventions were the product of this move. Constituting four separate documents, they expanded IHL to include a prohibition on the use of force against hospitals, prisoner of war camps, churches, and the sick and wounded (both on land and shipwrecked).[xxv]  However, it was in recognising civilians as a separate group to be protected that the Geneva Conventions truly made a mark.[xxvi] A follow-up to the 1949 Conventions, the 1977 Additional Protocol I codified the protection of civilians from all the effects of war and was seen by many international lawyers as a “repudiation of World War Two strategic bombing”.[xxvii] Still, nuclear weapons were intentionally bypassed in both the 1949 and 1977 conventions with the nuclear weapons states (of whom the US, France, India, Pakistan, Israel have not ratified the treaty) declaring that IHL “had no effect on use of nuclear weapons and neither regulated nor prohibited their use”.[xxviii] However, as the next section of this paper will show, this view is legally incorrect. This is due to the fact that in customary IHL there is a rule, known as the ‘Martens Clause’, that permits the application of IHL in instances where this is no specific prohibiting treaty.

Originally found in the preambles of both the 1899 and 1907 Hague Conventions, the Martens Clause (named after a Russian Foreign Minister) in effect states that “if a particular rule is not to be found in treaty law, belligerents remain under the protection and authority of customary international law, the principles of humanity, and the dictates of the public conscious”.[xxix] Since 1907 the Clause has been codified into Art 1(2) of the Additional Protocol 1 of 1977 and reads as follows: “In cases not covered by the Protocol or by other international agreements, civilians and combatants remain under the protection and authority of the principle of international law derived from established custom, from the principles of humanity and from the dictates of public conscience.”[xxx]

The ICJ affirmed the relevance and continued existence of this Clause in their 1996 Advisory Opinion on nuclear weapons declaring that it “has proved to be an effective means of addressing the rapid evolution of military technology”.[xxxi] For the case at hand, this means that humanitarian law, despite what nuclear weapons states may say, applies to any would-be use of a nuclear weapon. As such, it does not matter whether or not there is no express treaty provision on prohibiting (or for that matter permitting) the use of nuclear weapons. In other words, “…the novelty of a new weapon does not exempt it from the laws of war”.[xxxii] With that being said, this paper will now make the case that to use a nuclear weapon would be a contravention of IHL.

In rendering their decision in the 1996 ‘Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons’ the International Court of Justice (ICJ), after having reviewed the customary law and treaties that make-up IHL, concluded that in IHL there exists ‘four cardinal rules’.[xxxiii] The first is the requirement that in war states distinguish combatants from non-combatants. Codified in Article 48 of Protocol 1 the aim of this principle is the prohibiting of states directly targeting civilians. Nuclear weapons do not meet this requirement. As Meyrowitz writes, “it is hard to think of a nuclear weapon that would not [when used] produce extensive destruction of areas populated by civilians…”[xxxiv] Hospitals, the sick and wounded, prisoner of war camps, places of worship and civilian populations in general would be affected – if not by direct impact than by radioactive fallout.

The second rule is the prohibition on the use of indiscriminate weapons. With its roots dating back to the St. Petersburg Declaration and the 1907 Hague Convention, the ICJ, in its 1996 Advisory Opinion, wrote that “States must never make civilians the object of attack and must consequently never use weapons that are capable of distinguishing between civilians and military targets”.[xxxv] Writing in the Advisory Opinion, Judge Guillaume argued that “…customary international law contains only one absolute prohibition: that concerning the use of so-called ‘blind’ weapons which cannot distinguish between civilians and military targets”.[xxxvi] In other words, if a state uses an indiscriminate weapon such as a nuclear weapon, than this equates to a deliberate attack on civilians (this is a similar position taken by the Landmine Convention). A similar conclusion was reached in 1962 by a Japanese domestic court in the Shimoda case, which saw survivors of Hiroshima sue the government of Japan for compensation for their injuries.[xxxvii] Writing as obiter dicta the court ruled that the nuclear attacks on Japan were illegal under IHL as such actions constituted a form of indiscriminate bombing.[xxxviii]

The third rule of IHL is in regard to proportionality in the use of force. Essentially, this rule means that if military action leads to “expected collateral casualties exceeding [the] value of [the] military objective than it is unlawful.”[xxxix] The only way civilian casualties can be incurred is “if [a] weapon used is lawful to begin with and if the target chosen for attack is a military objective within the meaning of IHL”.[xl] However, as this paper has pointed out, the nature of a nuclear weapon (i.e. its indiscriminate effects) would render its users unable to rely on this exception. Lastly, the final rule is the prohibition on the use of weapons that cause unnecessary suffering, something which the ICJ calls the ‘cardinal principle’ of IHL.[xli] Dating back to the St. Petersburg Declaration, the reasoning behind this rule is straightforward: “weapons that render death inevitable are excessive to the needs of war” and are thereby illegal.[xlii] In writing his dissenting report to the Advisory Opinion, Judge Weeramantry concluded that “the facts…are more than sufficient to establish that nuclear weapons cause unnecessary suffering going far beyond the purposes of war.”[xliii] British international legal writers McCoubrey and White make a similar statement saying that, “the strong argument of unnecessary suffering, coupled with the inevitable escalatory effect of any use of nuclear weapons, tends to support at least a broad conclusion of use proscription.”[xliv]

In closing, this paper has made the argument that nuclear weapons are illegal under international humanitarian law. Article 1 of the Geneva Conventions, of which all nuclear states are a party too, states that the “High Contracting Parties undertake to respect and ensure respect for the present Convention in all circumstances” (author’s emphasis).[xlv] As such, IHL is binding on all states and, due to the Martens Clause, can, by default, prohibit specific weapons systems. This reasoning was also reached by the ICJ in their Advisory Opinion, when the Court concluded that prima facie the use of nuclear weapons would be a violation of IHL.[xlvi] Despite reaching that conclusion, the Court also went on to say that a state could still use nuclear weapons in the event of extreme situations of self-defence.[xlvii]However, as this paper has outlined, the existence of such a caveat discounts the entire body of IHL which tries to ensure international security by limiting the amounts of suffering states can inflict on one another. Nevertheless, it can still be said that when nuclear weapons are subjected to the corpus of IHL there clearly exists a legal imperative to rid the world of nuclear weapons.

[i] Warner, D., ‘The Nuclear Weapons Decision by the International Court of Justice: Locating the raison behind the raison d’etat’, Millennium, Volume 27, Number 2, 2000,p. 311

[ii] Burroughs, J., ‘The Advisory Opinion of the International Court of Justice and the Statute of the International Criminal Court’, June 15, 1999, Accessed March 20, 2011, Available at, p. 3

[iii] Sheldon, J., ‘Nuclear Weapons and the Laws of War: Does Customary International Law Prohibit the Use of Nuclear Weapons in all Circumstances?, Fordham International Law Journal, Volume 24, 1996-1997, p. 182

[iv] For an overview of the effects of a nuclear weapon detonation please read the Campaign for Nuclear Disarmament’s ‘The Effects of Nuclear Weapons’ webpage. Available at

[v] McCoubrey, H., and White, N., International Law And Armed Conflict, Dartmouth Publishing Company, 1992, p. 249; Meyrowitz, E.L., ‘The Opinions of Legal Scholars on the Legal Status of Nuclear Weapons’, Stanford Journal of International Law, Volume 24, 1987-1988, p. 114

[vi] Sheldon, p. 185

[vii] Due to space limitations this paper will not address the role of international law as it relates to self-defence or nuclear deterrence. For further information on these matters please read a special nuclear weapons issue of the International Review of the Red Cross, Volume 316, 1997, Available at

[viii] Morris, J., ‘Law, Politics, and the Use of Force’, in Baylis, J., Wirtz, J., and Gray, C (eds.), Strategy In The Contemporary World, Oxford University Press,2010, p. 111

[ix] McCoubrey and White, p. 189

[x] Morris, p. 118

[xi] McCoubrey and White, p. 189

[xii] Ibid., p. 189

[xiii] Morris, p. 118

[xiv] Burroughs, p. 1

[xv] Bleimaier, J., ‘Nuclear Weapons and Crimes Against Humanity Under International Law’, Catholic Lawyer, Volume 33, Number 2,1990, p. 162

[xvi] Ibid., p. 162

[xvii] Sheldon, p. 213

[xviii] Meyrowitz, E.L., ‘The Laws of War and Nuclear Weapons’, Brooklyn Journal of International Law, Volume 9, Number 2, 1983, p. 234; see also Sheldon, p. 213

[xix] Ibid., p. 233

[xx] Sheldon, p. 213

[xxi] Art.22: “the right of belligerents to adopt means of injuring the enemy is not unlimited.”

Art. 23(e): prohibits the use of “arms, projectiles or material calculated to cause unnecessary suffering.”

[xxii] Sheldon, p. 214

[xxiii] Burroughs, p. 1

[xxiv] Sheldon, p. 224

[xxv] Meyrowitz, 1983, p. 250

[xxvi] McCoubrey and White, p. 274

[xxvii] Burroughs, p. 1

[xxviii] Fujita, H., ‘The Advisory Opinion of the International Court of Justice on the legality of nuclear weapons’, International Review of the Red Cross, Volume 26, 1997, Available at, p. 2

[xxix] Doswald- Beck, L., ‘International humanitarian law and the Advisory Opinion of the International Court of Justice on the legality of the threat or use of nuclear weapons’, International Review of the Red Cross, Volume 316, 1997, Available at, pp. 7-8

[xxx] Warner, p. 309

[xxxi] Doswald-Beck, p. 8

[xxxii] Meyrowitz, 1987-1988, p. 116

[xxxiii] Doswald-Beck, p. 2

[xxxiv] Meyrowitz, 1983, p. 250

[xxxv] International Court of Justice, Advisory Opinion (Legality of the Threat or Use of Nuclear Weapons), 1996, Accessed March 11, 2011, Available at, para. 78

[xxxvi] Doswald-Beck, p. 2

[xxxvii] The 1952 American-Japanese peace agreement prevents Japanese citizens from suing the US government for injuries and damages inflicted during the course of the war.

[xxxviii] Tanaka, Y., and Falk, R., ‘The Atomic Bombing, The Tokyo War Crimes Tribunal and the Shimoda Case: Lessons for Anti-Nuclear Legal Movements’, JapanFocus, 2011, Accessed February 10, 2011, Available at, p. 2; Interestingly enough, in the Nuremberg and Tokyo War Crimes Tribunals charges relating to indiscriminate bombing during World War Two were intentionally avoided – the implication being that Allied nations would be also liable for such a charge.

[xxxix] Doswald-Beck, p. 5

[xl] Ibid., p. 5

[xli] International Court of Justice, para. 78

[xlii] Doswald-Beck, pp. 6-7

[xliii] Weeramantry, J., ‘Dissenting Opinion: Advisory Opinion (Legality of the Threat or Use of Nuclear Weapons), International Court of Justice,1996, Accessed March 11, 2011, Available at, p. 48

[xliv] McCoubrey and White, p. 250

[xlv] Morris, p. 119

[xlvi] International Court of Justice, para. 105

[xlvii] Ibid., para. 2E


One thought on “To Use or Not To Use Nuclear Weapons: A Question of Legality

  1. How do these prohibition laws act in battle field ? Who will follow and why ? The recent Iraq war , Libya war proved that these laws actually work ! ? A state has two kinds of threat 1. Internal 2. External . Nuclear weapon can not solve internal threat but it can resist external threat( USA invasion ) . When external threat will be vanished , every nation’s security and natural resource can be ensured then nuclear threat will be gone . We can expect these laws being followed .

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