Nuclear Weapons and its Problematic Implications
Updated: Jun 28
This paper aims to summarise the issues of the Legality of the Threat or Use of Nuclear Weapons advisory opinion (‘AO’) (1), the findings of the International Court of Justice (the ‘Court’) (2) and detail their implications on International law (3).
The Court was tasked to consider whether the threat or use of nuclear weapons could be permitted under international law.[i] In its determination the Court considered whether it had jurisdiction to provide an AO and whether the threat or use of nuclear weapons is consistent with the principles of self-defence and international humanitarian law (‘IHL’); both of which were held as customary international law (‘CIL’).[ii]
The ruling requested by the United Nations General Assembly (‘UNGA’), was critical given the potential for nuclear weapons to destroy both human civilizations and entire ecosystems.[iii]
There is no international law that specifically authorises the threat or use of nuclear weapons, nor does there exist law which universally prohibits said threat or use.[iv] Therefore, the legality of nuclear weapons falls on the specific circumstances involved.[v]
A. Whether the Court had jurisdiction to provide an AO on the basis of a UNGA request?
B. Whether the threat or use of nuclear weapons could be permitted under international law?
The jurisdictional consideration in this case fell upon whether there was a “legal question” and whether the request came from an authorised body under Article 65(1) of the ICJ Statute.[vi]
The Court held the UNGA was authorised to request an AO under Article 96(1) of the United Nations Charter (‘UN Charter’).[vii] Further, the Court in following its Western Sahara AO, found the request indeed pertained to a “legal question” as it was of legal character, requiring consideration of the compatibility of nuclear weapons with international law.[viii] While the question also had political aspects, this did not deprive it of its legal character.[ix]
As such, the Court held it could give an AO as per the request of the UNGA.[x]
B. Legality of Nuclear Weapons in IL
Through its adoption of the S.S. Lotus principle, the Court held that States could threat and use nuclear weapons absent of a prohibition under international law.[xi] However, the Court noted the right to adopt means of injuring the enemy is limited by existing laws.[xii]
Some States argued the right to life under the International Covenant on Civil and Political Rights should be considered, however the Court highlighted the instrument regulated peacetime, whereby unlawful loss of life in hostilities was a question of IHL.[xiii] Further, the prohibition against genocide was a circumstantial question of intent, rather than one of the choice of weapon.[xiv]
Additionally, the Court refused to consider environmental law as they could not deprive a State of its right to self-defence.[xv] Additionally, IHL protects against widespread, long-term, and severe damage to the natural environment under Article 35 and 55 of Additional Protocol I.[xvi]
Moreover, there is no express prohibition against nuclear weapons, as is the case with poisoned, chemical, or bacteriological weapons,[xvii] nor is there collective agreement between States in the form of treaties which would constitute a universal prohibition.[xviii]
Accordingly, the Court ruled that the most directly relevant applicable law under CIL was that which governs the threat or use of force in the UN Charter (a), and that which governs armed conflicts under IHL and the principle of neutrality (b).[xix]
In its considerations, the Court stressed the unique characteristics of nuclear weapons which cause an immense initial release of energy and prolonged radiation, the destructive potential of which is potentially catastrophic.[xx]
a. UN Charter
As to whether the threat or use of nuclear weapons was contrary to the UN Charter, the Court was tasked to determine whether a breach of Article 2(4) using nuclear weapons could be justified by self-defence under Article 51.[xxi] More specifically, whether the threat or use of nuclear weapons could conform with the conditions of necessity and proportionality under CIL.[xxii]
In respect to threats, the Court held that a threat to use nuclear weapons in a way which would violate the UN Charter would be contrary to international law, and that this may apply to possession in such circumstances.[xxiii] While the Court stressed lawful threat or use is extremely unlikely, they were unable to definitively conclude the legality of nuclear weapons in extreme circumstances of self-defence, where the survival of a State is at risk.[xxiv]
b. IHL and Neutrality
In respect to nuclear weapons and their compliance with the laws and customs of war under CIL, the Court considered the “cardinal principles” of distinction and avoidance of unnecessary suffering.[xxv] Further, the Court held that neutrality, ensuring respect to neutral State territories was inviolable and applicable to nuclear weapons.[xxvi]
Unfortunately, the Court was unable to provide a conclusive determination on this issue and held that nuclear weapons do not necessarily violate these principles; as such a conclusion is dependent on the specific circumstances of their threat or use.[xxvii]
3. Critical Implications
Given its broad application of S.S. Lotus principle,[xxviii] the Court could not conclude whether in extreme or very specific circumstances, the threat or use of nuclear weapons would be permitted under international law.[xxix]
While the Court unanimously agreed that there exists an obligation for States to pursue nuclear disarmament,[xxx] absent of regulation at a conventional level, States are left to subjectively apply existing CIL principles to complex weaponry related issues. This finding has critical implications on the use of weapons under international law, as invocations of universal principles are insufficient to regulate State action.[xxxi]
For example, fully autonomous lethal weapon systems (‘FAWS’) lack conventional level regulation.[xxxii] For said weapons to adequately comply with international law, existing principles need be supplemented by a framework concerning the unique characteristics of the weapon.[xxxiii]
A critical distinction between FAWS and nuclear weapons is that FAWS may minimise humanitarian consequences through their superior efficacy,[xxxiv] whereas nuclear weapons have far-reaching consequences due to the radiation they create.[xxxv]
Written by Dan Canta
Chief Publications Officer
[i] Legality of the Threat or Use of Nuclear Weapons (Advisory Opinion)  ICJ Rep 226 (‘NWAO’) . [ii] NWAO (n 1) , . [iii] NWAO (n 1) -. [iv] NWAO (n 1) 266. [v] NWAO (n 1) 266. [vi] NWAO (n 1) . [vii] NWAO (n 1) . [viii] NWAO (n 1) . [ix] NWAO (n 1) . [x] NWAO (n 1) . [xi] NWAO (n 1) . [xii] NWAO (n 1) , . [xiii] NWAO (n 1) -. [xiv] NWAO (n 1) . [xv] NWAO (n 1) . [xvi] NWAO (n 1) . [xvii] NWAO (n 1) -. [xviii] NWAO (n 1) -, -, . [xix] NWAO (n 1) . [xx] NWAO (n 1) -. [xxi] NWAO (n 1) -. [xxii] Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America) (Merits)  ICJ Rep 14 ; NWAO (n 1) . [xxiii] NWAO (n 1) -. [xxiv] NWAO (n 1) . [xxv] NWAO (n 1) . [xxvi] NWAO (n 1) -. [xxvii] NWAO (n 1) -. [xxviii] NWAO (n 1) -. [xxix] NWAO (n 1) 266. [xxx] NWAO (n 1) 267. [xxxi] Brad R Roth, Sovereign Equality and Moral Disagreement (Oxford University Press, 3 November 2011) 271; International Committee of the Red Cross (ICRC), Report on ICRC Expert Meeting on ‘Autonomous weapon systems: technical, military, legal and humanitarian aspects (Summary Report, 9 May 2014) (‘ICRC Report 2014’) 14. [xxxii] Neil Davison, ‘A legal perspective: Autonomous weapon system under international humanitarian law’ (2018) International Committee of Red Cross 9; Alexandra Brzozowski, No progress in UN talks on regulating lethal autonomous weapons (News Article, 22 November 2019) <https://www.euractiv.com/section/global-europe/news/no-progress-in-un-talks-on-regulating-lethal-autonomous-weapons/>. [xxxiii] ICRC Report 2014 (n 31) 15-16; Merel Ekelhof, Autonomous weapons: Operationalizing meaningful human control (Blog Post, 15 August 2018) <https://blogs.icrc.org/law-and-policy/2018/08/15/autonomous-weapons-operationalizing-meaningful-human-control/>. [xxxiv] ICRC, Artificial intelligence and machine learning in armed conflict: A human-centred approach (Report, June 2019) 2; ICRC Report 2014 (n 31) 1. [xxxv] Louise G. Maresca, Nuclear weapons: 20 years since the ICJ advisory opinion and still difficult to reconcile with international humanitarian law (Blog Post, 8 July 2016) < https://blogs.icrc.org/law-and-policy/2016/07/08/nuclear-weapons-20-years-icj-opinion/>.