Nukes: Still legal, for some.

Part 1

NPT, TPNW, ICJ, Nuclear Weapons, Advisory Opinion, Marshall Islands, Conflict and Security Law, Jus in Bello, Jus ad Bellum, Arms Control, Use of Force, Self-Defence, IHL, IHRL, Customary International Law, Specially Affected States and UK nuclear weapon policy.

The Treaty on the Prohibition of Nuclear Weapons (TPNW) enters into force on 22 January 2021. The first of two articles explains the legal history leading to the TPNW and the impact of the TPNW. The second article explains why nuclear weapons will remain legal for some States, and what policy responses the UK should consider.

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1. WHAT IS THE EXISTING NUCLEAR WEAPON LEGAL ARCHITECTURE?

It is appropriate to situate the TPNW within the international legal architecture. This article identifies two key starting points. First, the Non-Proliferation Treaty[1] (NPT) and the International Court of Justice’s (ICJ) position in the 1996 Advisory Opinion on Nuclear Weapons[2] and the subsequent Marshall Islands cases.

The NPT, now 50 years old is an example of Cold War co-operation. It is considered by the UN and its watchdog[3] as the centrepiece of global efforts to prevent further spread of nuclear weapons.[4] It is conceptualised within three coalescing pillars; non-proliferation, disarmament and peaceful use of nuclear technology.[5] By virtue of 191 State parties it can be considered a success, but; it is not universal;[6]  States have acted unfaithfully;[7] and [unlikely] reform is needed in light of modernisation of technology.[8] By preventing the spread of nuclear weapon technology the NPT represented the widest piece of fabric in the nuclear weapon disarmament legal patchwork. Though its preamble includes the strategic desire to rid the world of nuclear weapons,[9] subsequent practice pragmatically and tactically focused on the non-proliferation pillar, likely in an effort to galvanize universality [think both historical context and of the Clausewitzian[10] doctrine]. This however compromised the strategic end-state of a nuclear weapon free world; Article VI[11] of the Treaty went largely unimplemented.

Article VI NPT:

Each of the Parties to the Treaty undertakes to pursue negotiations in good faith on effective measures relating to cessation of the nuclear arms race at an early date and to nuclear disarmament, and on a treaty on general and complete disarmament under strict and effective international control.

The 1996 Advisory Opinion was the ICJ’s attempt at considering the legality of nuclear weapons under existing international law (lex lata), and not as what many wished the law to be (lex desiderata). For the purposes of this article, the judgment ultimately stated two key points. First, nuclear weapon use in an international armed conflict would be regulated by existing ‘principles of international law applicable in armed conflict… particularly international humanitarian law[12] (IHL), confirming that their use would generally be contrary to the jus in bello rules. There are oft-cited exceptions to this,[13] including Judge Schwebel’s own speculations.[14] Second, the court recognised a State’s inherent UN Charter Article 51 right[15] to self-defence, but issued a critically received[16] non-liquet on whether nuclear weapon use would be lawful in an extreme case of self-defence – necessity ad bellum. The vote was split seven votes to seven, by the President’s casting vote.[17] In short, in an act of juridical deference to international legislatures, the ICJ confirmed nuclear weapons cannot be said to be illegal in all circumstances. President Bedjaoui declared the court does no more than place on record the existence of a legal uncertainty.[18]

Tying the Advisory Opinion together to the NPT, the court went on to unanimously answer a question it had not been asked to consider. It produced an analysis of the nature of the obligation to negotiate disarmament under Article VI of NPT. The legal import of that obligation, in the court’s opinion, goes beyond that of a mere obligation of conduct, but an obligation of result: nuclear disarmament in all its aspects.[19] President Bedjaoui stated that this obligation, in his view, assumed customary force.[20]

The question of interpreting this obligation is what opened the Marshall Islands litigation before the ICJ in 2014. In the case, the Marshall Islands, a tiny Pacific Ocean island country affected by the impact of nuclear weapon testing, filed applications against the nine nuclear weapon States, accusing them of not fulfilling their obligations with respect to the ‘cessation of the nuclear arms race at an early date and to nuclear disarmament’.[21] Only three (India, Pakistan and the UK) of the nine of the States recognised compulsory jurisdiction of the Court pursuant to Article 36(2) of its Statute,[22] with the other six refusing voluntary jurisdiction. The Marshall Islands alleged that the UK had violated Article VI of the NPT,[23] with India and Pakistan (not party to the NPT) violating the obligation in customary international law[24] – as identified by President Bedjaoui ten years earlier in the Advisory Opinion.

On 5 October 2016, in another split vote, by the President’s casting vote, the Court upheld[25] the respondent States’ preliminary objections based on the absence of a dispute between the Marshall Islands on one hand, and the three nuclear States on the other; a procedural technicality under Article 79 of the Rules of the Court.[26] This is remarkable for two reasons. First, it is remarkable that a jurisdictional issue would give rise to a split vote. Second, the minority judges were not only disappointed, but angry, that on procedural formalities the court is deciding not go into a matter which is of great important for the world.

In dissenting, Judge Bennouna said

[…] International judges had a duty to be even more vigilant in the present case, which concerns a question of crucial importance for security in the world. That is another reason for the principal judicial organ of the United Nations to undertake its role fully. Indeed, how can it shelter behind purely formalistic considerations which both legal professionals and ordinary citizens would find difficult to understand, rather than contributing, as it should do, to peace through international law, which is the raison d’être of the Court.[27] […]

As academic Andrea Bianchi later wrote

It makes a bad impression to avoid decisions on “big cases,” to stay clear of issues that are sensitive to big powers. One is left with a sense of uneasiness to find out that in this particular case the five judges who are nationals of the five permanent members of the Security Council—incidentally all nuclear powers—have unashamedly all sided with the majority to dismiss the case. Of course, this may be thought to be a coincidence. But whom do you expect to believe that this might actually be the case?[28]

It is disappointing that the Court did not attempt to clarify its Advisory Opinion and to show the world what the solution to nuclear weapons should be.

It is against this backdrop that many people, particularly young people, have galvanised around the International Campaign to Abolish Nuclear Weapons (ICAN).[29] The campaign successfully lobbied for the UN General Assembly to adopt a landmark resolution in December 2016 to launch negotiations on “a legally binding instrument to prohibit nuclear weapons.”[30]

2. WHAT IS THE TREATY ON THE PROHIBITION OF NUCLEAR WEAPONS?

The treaty was negotiated at the United Nations headquarters in New York in March, June and July 2017, with the participation of more than 135 nations, as well as members of civil society.[31] No nuclear-armed State participated, and the Netherlands was the only NATO country that took part,[32] but voted against it – the only State to do so. It opened for signature on 20 September 2017.[33] The Treaty on the Prohibition of Nuclear Weapons is the instrument that represents the next incremental leap from the NPT in implementing the overall strategy of disarmament, and can be seen as putting the NPT Article VI into practice;[34] filling the last legal gap.[35]

Following the 50th ratification[36] by Honduras on October 24 2020, marking the TPNW’s entry into force 90 days later on the 22 January, some commentators explicitly[37] or by implication[38] stated there will be a ban on nuclear weapons that applies to all States. What does this mean, and is it true? Does this represent an emergence of an updated lex lata specifically prohibiting nuclear weapons? How are tensions of nascent opinio juris on one hand and strong adherence to the practice of the deterrence on the other reconciled? What other disarmament strategies could be considered? There are a lot of questions that can be generated, but this section will proceed with focus on the textual detail of the TPNW, whilst section 3 will return to some of these questions in answering why nuclear weapons will remain legal for some.

In summary, the Treaty;[39]

Prohibits the developing, testing, producing, manufacturing, otherwise acquiring, possessing, stockpiling, transferring and receiving nuclear weapons. It further bars states from assisting, encouraging or inducing anyone to engage in any activity prohibited by the treaty, and seeking or receiving any assistance, in any way, from anyone to engage in activity prohibited under the treaty. The treaty also prohibits state parties from allowing another state to station, install or deploy nuclear weapons in its territory. Most notably, the treaty completely bans using or threatening to use nuclear weapons. Simply put the treaty seeks the total elimination of nuclear weapons to ensure they are never used again.[40]

The nature of the undertaking “never under any circumstances” in the chapeau of Article 1(1) is all-encompassing, permitting no exception, even in response to aggression (ad bellum) or as a belligerent reprisal within an armed conflict (in bello)[41] – this is a direct response to the two key conclusionary points previously identified in the ICJ’s Advisory Opinion. 

In attempting to ban the outright use of an entire category of weapon, the TPNW joins the Biological Weapons Convention (BWC) [1972],[42] the Chemical Weapons Convention (CWC) [1993],[43] the Ottawa (Mine-Ban) Convention [1999],[44] and the Convention on Cluster Munitions (CCM) [2010].[45] Unlike these Treaties however, the TPNW only has 51 ratifications. Both the BWC and CWC have near universal support, with 183 and 193 parties respectively, including the P5. 164 States are party to the Ottawa Convention, with 110 to the CCM. Russia, China and United States are not a party to either. The TPNW adopts much of the same language as the previous arms control Conventions, for example all Conventions contain exactly the same wording in regards to ‘assisting, encouraging or inducing, in any way, anyone to engage in any activity prohibited to a State Party under the respective Convention’.[46] Similar language is found in reporting obligations,[47] but critically, not with inspection obligations.

It is almost certain that the TPNW will achieve at least another 30 State parties within the next 1-3 years, and more in the longer term. Equaled in certainty is the realpolitik that nuclear weapons States will not sign up to it, nor is it likely that those under nuclear umbrella protection will. Even the 122 States that voted for it at the General Assembly were far from unanimous.[48] This being said, there are legal, political and economic tipping points that will be considered in the next article. The second article will consider recommendations on how the UK should proactively respond.


[1] Non-Proliferation Treaty 1970 NPT Treaty (un.org)

[2] ICJ Advisory Opinion, Legality of the Threat or Use of Nuclear Weapons [1996] 095-19960708-ADV-01-00-EN.pdf (icj-cij.org)

[3] IAEA International Atomic Energy Agency | Atoms for Peace and Development (iaea.org)

[4] IAEA, NPT Treaty on the Non-Proliferation of Nuclear Weapons (NPT) | IAEA

[5] Nukespt, The Pillars THE PILLARS – The NPT (weebly.com)

[6] India, Pakistan, North Korea, Israel and South Sudan.

[7] Reuters, Fearing Nuclear Proliferation, Europe Scrambles to Calm Iran Tensions [2021] Fearing nuclear proliferation, Europe scrambles to calm Iran tensions | Reuters

[8] Stuart Casey-Maslen, ‘The Status of Nuclear Deterrence Under International Law in the Light of the Treaty on the Prohibition of Nuclear Weapons’ in Yearbook of International Humanitarian Law [2018].

[9] Preamble, Non-Proliferation Treaty 1970 NPT Treaty (un.org)

[10] Anatol Rapoport, ‘International Relations and Game Theory’ in Arms Control and Disarmament [2018]

[11] Art 6, Non-Proliferation Treaty 1970 NPT Treaty (un.org)

[12] ICJ Advisory Opinion, Legality of the Threat or Use of Nuclear Weapons [1996] at Para 101, D, A 095-19960708-ADV-01-00-EN.pdf (icj-cij.org)

[13] Krasny, Do Tactical Nukes Break International Law [2020] Do tactical nukes break international law? – Bulletin of the Atomic Scientists (thebulletin.org)

[14] Dissenting Opinion of Judge Schwebel [1996] 095-19960708-ADV-01-09-EN.pdf (icj-cij.org)

[15] ICJ Advisory Opinion, Legality of the Threat or Use of Nuclear Weapons [1996] at Para 38 095-19960708-ADV-01-00-EN.pdf (icj-cij.org)

[16] McCormack, A Non-Liquet on Nuclear Weapons [1997] A non liquet on nuclear weapons – The ICJ avoids the application of general principles of international humanitarian law- ICRC

[17] ICJ Advisory Opinion, Legality of the Threat or Use of Nuclear Weapons [1996] at Para 101, D, A 095-19960708-ADV-01-00-EN.pdf (icj-cij.org)

[18] President Bedjaoui Declaration [1996] 095-19960708-ADV-01-01-EN.pdf (icj-cij.org)

[19] ICJ Advisory Opinion, Legality of the Threat or Use of Nuclear Weapons [1996] at Paras 98-103 095-19960708-ADV-01-00-EN.pdf (icj-cij.org)

[20] Ibid 18

[21] ICJ, Obligations Concerning Negotiations Relating to Cessation of the Nuclear Arms Race and to Nuclear Disarmament at Para 1 [2016] CIJ-Ordonnance1107.pdf (icj-cij.org)

[22] Art 36(2) ICJ Statute Statute of the Court | International Court of Justice (icj-cij.org)

[23] ICJ, Obligations Concerning Negotiations Relating to Cessation of the Nuclear Arms Race and to Nuclear Disarmament at Para 11 [2016] CIJ-Ordonnance1107.pdf (icj-cij.org)

[24] ICJ, Obligations Concerning Negotiations Relating to Cessation of the Nuclear Arms Race and to Nuclear Disarmament at Para 12 [2016] CIJ-Ordonnance1107.pdf (icj-cij.org)

[25] ICJ, Obligations Concerning Negotiations Relating to Cessation of the Nuclear Arms Race and to Nuclear Disarmament at Para 59 [2016] CIJ-Ordonnance1107.pdf (icj-cij.org)

[26] Art 79 Rules of the Court Rules of Court | International Court of Justice (icj-cij.org)

[27] Dissenting Opinion of Judge Bennouna, [2016] CIJ-Ordonnance1107.pdf (icj-cij.org)

[28] Bianchi, Choices and (the awareness of) its Consequences: The ICJ’s “Structural Bias” Strikes Again in the Marshall Islands Case [2017] Choice and (the Awareness of) its Consequences: The ICJ’s “Structural Bias” Strikes Again in the Marshall Islands Case | American Journal of International Law | Cambridge Core

[29] ICAN ICAN (icanw.org)

[30] ICAN, The Campaign The campaign – ICAN (icanw.org)

[31] ICAN, The Treaty The Treaty – ICAN (icanw.org)

[32] UN, Review Conference of the Parties to the Treaty on the Non-Proliferation Treaty United Nations Conference to Negotiate a Legally Binding Instrument to Prohibit Nuclear Weapons, Leading Towards their Total Elimination – Participants

[33] ICAN, The Treaty The Treaty – ICAN (icanw.org)

[34] Erasto, The NPT and the TPNW: Compatible or conflicting nuclear weapons treaties? [2019] The NPT and the TPNW: Compatible or conflicting nuclear weapons treaties? | SIPRI

[35] Kimball, A Turning Point in the Struggle Against the Bomb: The Nuclear Ban Treaty Ready to Go Into Effect [2020] A Turning Point in the Struggle Against the Bomb: The Nuclear Ban Treaty Ready to Go Into Effect – Just Security

[36] Article 15, Treaty on the Prohibition on Nuclear Weapons [2021] A/CONF.229/2017/8 – E – A/CONF.229/2017/8 -Desktop (undocs.org)

[37] Beatrice Fihn, Executive Director of the International Campaign to Abolish Nuclear Weapons (ICAN)

[38] ICRC, Tweet 24 October 2020 ICRC on Twitter: “We banned the bomb! A rare piece of good news in 2020: nuclear weapons are about to become illegal, after the 50th State ratified the #NuclearBan. https://t.co/zFS7WYQ0Ua” / Twitter

[39] Treaty on the Prohibition on Nuclear Weapons [2021] A/CONF.229/2017/8 – E – A/CONF.229/2017/8 -Desktop (undocs.org)

[40] Johnson and Tregle ‘The Treaty on the Prohibition of Nuclear Weapons on its Limited Impact on the Legality of their Use’ [2020] The Treaty on the Prohibition of Nuclear Weapons and its Limited Impact on the Legality of their Use (justsecurity.org)

[41] Stuart Casey-Maslen, ‘The Status of Nuclear Deterrence Under International Law in the Light of the Treaty on the Prohibition of Nuclear Weapons’ in Yearbook of International Humanitarian Law [2018].

[42] Biological Weapons Convention 1972 BWC-text-English.pdf (un-arm.org)

[43] Chemical Weapons Convention 1993 Chemical Weapons Convention (opcw.org)

[44] Convention on the Prohibition of the Use of Anti-Personnel Mines 1999 treatyenglish.pdf (icbl.org)

[45] Convention on Cluster Munitions 2008 DIPLOMATIC CONFERENCE FOR THE ADOPTION OF A CONVENTION ON CLUSTER MUNITIONS (clusterconvention.org)

[46] Art 1(E) Treaty on the Prohibition of Nuclear Weapons [2021] Show Treaty (un.org)

[47] Art 4(1) and (5) Treaty on the Prohibition of Nuclear Weapons [2021] Show Treaty (un.org)

[48] Fleck, The Treaty on the Prohibition of Nuclear Weapons: Challenges for International Law and Security in Nuclear Non-Proliferation in International Law Pg 402

Published by Luke James

Visiting Professional Political and Security analyst at the ICC, research associate Center for the Study of Democracy, Defence Human Security Advisor Legal research interests in conflict and security law, emerging technologies and the intersection with human security.

2 thoughts on “Nukes: Still legal, for some.

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