Deficiencies and Ambiguities of the Treaty on the Prohibition of Nuclear Weapons

by | Sep 30, 2022

TPNW - Nuclear Weapons

Touted as an effort to “reframe the debate on nuclear weapons,” the Treaty on the Prohibition of Nuclear Weapons (TPNW) has currently accumulated 66 ratifications, a little over a year after having reached the threshold of 50 ratifications when Honduras deposited its ratification on 23 October 2020. It entered into force on 22 June 2021, “90 days after the fiftieth instrument of ratification, acceptance, approval or accession has been deposited” (Art. 15 (1)). While the TPNW was concluded at a blitz negotiating conference which lasted for 21 working days, the ratification process leading to its entry into force was much slower than that of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). As of November 2021, 191 States have ratified the NPT. While the NPT has been in force since 1970, it also demonstrated a higher pace of ratifications leading to its entry into force – 61 in 18 months, as opposed to 50 in 37 months in the case of the TPNW.

What may be a more discouraging statistic for the TPNW is the conspicuous decrease in the pace of ratifications. In 2021, there were eight and in 2022, as of the time of writing, there were seven, whereas in 2020, despite the global focus on the COVID-19 pandemic, 17 States deposited their instruments of ratification, with 15 in 2019 and 16 in 2018. And yet, the TPNW may have been the most apparent, if only single, normative achievement in disarmament in the 21st century, apart from the entry into force of the treaties establishing nuclear-weapon-free zones in Africa and in Central Asia, the conclusion of several regional acts on regulation of small arms and light weapons (see here, here), and the extension, almost literally at the eleventh hour, of the Treaty between the United States of America and the Russian Federation on Measures for the Further Reduction and Limitation of Strategic Offensive Arms, also known as the New START Treaty.

Conversely, the same period witnessed the abrogation or rendering irrelevant of treaties on the limitation of anti-ballistic missile systems, on the elimination of intermediate and shorter-range missiles, on conventional forces in Europe (see here and here), and on “open skies.” The broadly supported Comprehensive Nuclear-Test-Ban Treaty (CTBT) is still in limbo with dim prospects of its entry into force.

Against this grim background, the speedy conclusion of the TPNW could have counted as a modest success story or a glimpse of light at the end of the tunnel had it not been for flawed goal setting, as well as deficiencies of the very text of the Treaty, which the First Meeting of States Parties held on 21-23 June, 2022 failed to ameliorate. This post highlights these shortcomings and advises that States expand restrictions and prohibitions on nuclear weapons, but not at the expense or to the detriment of existing or nascent regulatory regimes, such as the NPT, the CTBT, regional nuclear-weapon-free zones, or non-treaty regimes designed to prevent proliferation. 

Fundamental Textual Deficiency

The TPNW sets an overarching and ambitious goal of a comprehensive ban on any nuclear-weapons-related activity, ranging from development and testing (Art. 1, para. 1(a)), to use or threat of use (Art. 1, para. 1(d)), to “stationing, installation or deployment” (Art. 1, para. 1(g)). Incidentally, there is no para. 2 in Art. 1, which is a rather unusual manner of assigning numbers to treaty provisions. But this is a lesser deficiency of the opening part of the text, which is overshadowed by a total absence of definitions, first and foremost of a “nuclear weapon” itself.

One might argue that the NPT, to which the TPNW refers in its own preamble as “the cornerstone of the nuclear disarmament and non-proliferation regime,” does not offer any such definition either. However, its “preparatory work,” to use the term of Article 32 of the Vienna Convention on the Law of Treaties (VCLT), reveals that the description of a nuclear weapon offered by William C. Foster, the lead negotiator for the United States, was unopposed and may be viewed as reflecting a consensus reached by delegations at the negotiating forum—the Conference of the Eighteen-Nation Committee on Disarmament. Foster, an MIT graduate with a degree in chemical engineering, stated that

all nuclear weapons have one characteristic in common. This is the characteristic that upon activation of a prearranged trigger mechanism they can release large quantities of energy in a very short period of time from sources of relatively small volume and light weight. They are enormously concentrated sources of explosive energy.

As George Bunn and Roland Timerbaev, members of, respectively, the U.S. and Soviet delegations that negotiated the NPT both at the Eighteen-Nation Committee and in bi-lateral talks that paved the way to the eventual conclusion of the Treaty, remark, the definitional stumbling block could be removed by relying on the “negotiating history … of the NPT to establish the intended coverage of the treaty.” While Bunn and Timerbaev were discussing the then-prospective CTBT, their observation could be well applied to the TPNW.

Absence of a definition of a nuclear weapon in the NPT notwithstanding, the concurrently negotiated Treaty for the Prohibition of Nuclear Weapons in Latin America, later adding “and the Caribbean” to its title (Treaty of Tlatelolko), does contain such a definition, as do subsequent nuclear-weapon-free zone treaties (South Pacific Nuclear Free Zone Treaty; African Nuclear Weapon Free Zone Treaty; Treaty on the Southeast Asia Nuclear Weapon-Free Zone; Treaty on Nuclear-Weapon-Free Zone in Central Asia).

During the TPNW negotiations Sweden submitted a draft definition of a nuclear weapon as an “assembly that is capable of producing an explosion and massive damage and destruction by the sudden release of energy instantaneously released from self-sustaining nuclear fission and/or fusion. It does not include the means of transport or delivery of such an assembly if separable from and not an indivisible part of it.” However, it was not included into the adopted text.

Whether the TPNW could benefit, as per the suggestion of Bunn and Timerbaev, from the NPT negotiating history, might depend on the interpretation of Art. 18 which states that its implementation “shall not prejudice obligations undertaken by States Parties with regard to existing international agreements, to which they are party,” but makes it contingent on “those obligations [being] consistent with the Treaty.” As stated by the delegation of Sweden at the TPNW negotiating conference,

We are not in full agreement with the language in article 18. We had a strong preference to delete the words after the last comma. The NPT and CTBT remain fully applicable even after this treaty enters into force. Nothing in this treaty can be interpreted as reducing the obligations of states parties to the NPT and CTBT.

Or, could the precedence clause of the TPNW be stretched as far as appropriating prevalence of its own negotiating history over that of other treaties?

Any claim of ostensible precedence of the TPNW should be at odds with the negotiating conference mandate, which reaffirmed “the importance of the Treaty on the Non-Proliferation of Nuclear Weapons and the commitments made therein, and considers that the pursuit of any such measures, provisions and norms should complement and strengthen the nuclear disarmament and non-proliferation regime, including the three pillars of the Treaty.”

Other Textual Deficiencies

Apart from that fundamental textual flaw of the TPNW, there are quite a few others that deserve mentioning, if only in the most cursory manner and in question mode.[i]

First, what are “other nuclear explosive devices”? Are they devices used in the so-called “peaceful nuclear explosions,” which should be banned by the CTBT with a notable exception, under Article VIII(1), of a possible permission to conduct an underground nuclear explosion for peaceful purposes, when and if it comes into force? Or are they something else, as Art. 1 para. 1(d) may suggest where it qualifies them as means of hostile use or threat of use? Again, a look at the negotiating history of the NPT could be quite helpful were it considered of relevance to the TPNW in light of its Art. 18 “precedence clause.”

Second, what are the differences in legal status of weapons and devices that are “owned, possessed or controlled” by a State party (Arts. 2 and 4)? Did the drafters use those terms consciously, in particular with respect to “possession” versus “ownership”? If they did, why is ownership omitted in Art. 1, para 1(a)? By the same token, did the drafters draw a clear distinction between “stationing,” “installation,” and “deployment” of nuclear weapons (Art. 1, para. 1(g))?

Third, what is a “competent international authority” (Art. 6) with broadly defined powers not only to verify, but also to negotiate the “irreversible elimination of nuclear-weapon programs” (Art. 4 (6)) and why, in a single instance (Art. 4 (6)), is the term used in plural?

Fourth, another example of what appears as an arbitrary use of terms is the obligation of States parties, under Art. 6(1), to provide assistance to individuals “affected by the use or testing of nuclear weapons in accordance with applicable international humanitarian law.” Assuming that international humanitarian law (IHL) operates in the context of an armed conflict, that provision, on its face, applies to a single State against which nuclear weapons had been used in anger. And that State – Japan – is not expected to become a TPNW party any time soon. Furthermore, modern IHL is to a large extent a product of post-Second-World-War normative development, starting with the four Geneva Conventions of 1949. Unless specifically provided, it may not apply retroactively. And yet an observer, if only an over-zealous pedant, might get an impression that the TPNW attempts to attribute to other treaties the force of ex post facto law.

Fifth, shall “a legally binding, time-bound plan” for elimination of a nuclear-weapon program referred to in Art. 4(2) be implemented by means of “additional protocols” to the TPNW envisaged in Art. 8 (para. 1(b))? If so, then should conclusion of several bilateral protocols between States parties and a yet-unknown entity be hypothetically expected?

Sixth, what is “any place under [a State’s] jurisdiction or control” referenced in Art. 1 (para. 1(g)) et sequentia, apart from the term being borrowed from the BTWC and the CWC? Read in conjunction with “deployment,” that provision might imply not only restrictions on the right of innocent passage, but also interference with the freedom of navigation through waters and airspace beyond the territorial sea. Did the drafters bear in mind the UN Convention on the Law of the Sea while pondering that provision? Of course, the Convention provides for certain restrictions on nuclear-powered ships or ships carrying nuclear materials, but it does not totally deny them the right of innocent passage through foreign territorial seas, let alone waters beyond its outer limit. On the other hand, for want of clarity the TPNW text may raise legitimate concerns about lack of explicit prohibition of transit of nuclear weapons or, for that matter, of “other nuclear explosive devices” through the ground territory of a State party or airspace above it.

Finally respecting the ambiguities of the TPNW text, it appears that the Treaty, unlike other treaties regulating weapons, in particular conventions banning two other known classes of WMDs, offers a surprisingly simplified procedure of withdrawal. It is rather easy to bring it into force – 90 days upon deposit of 50 unqualified ratifications, unlike the NPT which required ratifications by the three depositaries and 40 other states, or the CWC which could only enter into force 180 days after the date of the deposit of the 65th instrument of ratification, or, as stated earlier, the CTBT which cannot enter into force although it boasts an impressive 170 ratifications. The TPNW is still easier to disengage from, even though the time span between notification of withdrawal and the date the withdrawal becomes effective is 12 months for the TPNW and 90 days for the BTWC and the CWC. To withdraw from the TPNW, a State Party would need to give notice to the Depositary (the UN Secretary-General) stating “the extraordinary events that it regards as having jeopardized its supreme interests” (Art. 17 (2)). Withdrawal procedure under the NPT and BTWC is more elaborate. A State Party willing to exercise that right would have to transmit a statement of extraordinary circumstances to all other States Parties, as well as to the UN Security Council, which implies the three depositaries – the Russian Federation, the United Kingdom, and the United States. As to the CWC, a withdrawing State Party would be obliged to notify all other States, the Executive Council of the Organization for the Prohibition of Chemical Weapons, the Depositary (the UN Secretary-General), and the UN Security Council.

TPNW and Customary International Law

A considerable body of literature already discusses the prospects of the TPNW, or particular norms thereof, eventually becoming customary international law (see for example here, here, and here). Authors, relying on the jurisprudence of the International Court of Justice (ICJ) and opinions expressed by the International Law Commission, revert, in greater or lesser detail, to the notions of “specially affected state” (North Sea Continental Shelf) and “persistent objector state.” While former NATO Legal Adviser, Steven Hill writes that “these concepts are distinct and must be analysed separately,” he then seems to merge them when admitting that

there is a strong argument that states with nuclear weapons and those in a nuclear alliance would be specially affected by a proposed ban on nuclear weapons. Even if a rule is indeed created, states that have objected to a certain degree to its emergence – so-called persistent objectors – will not be bound by it.

In the case of the TPNW it may be fair to also refer to “preemptive persistent objector states,” since all five formally recognized nuclear-weapon States, jointly and some individually, formally rejected the TPNW prior to its entry into force, while three of them – France, the United Kingdom, and the United States – were also joined by those allied with them by virtue of NATO membership. On 24 October 2018, in a rare show of unanimity, five permanent members of the UN Security Council adopted on often-cited Joint Statement on the Treaty on the Non-Proliferation of Nuclear Weapons asserting that they “will not support, sign or ratify this Treaty. The TPNW will not be binding on our countries, and we do not accept any claim that it contributes to the development of customary international law; nor does it set any new standards or norms.”

That Statement is reflected in the Russian official position regarding the TPNW, as presented by the spokesperson of the Foreign Ministry: “Russia will not support, sign or ratify this Treaty. It will not be binding for the Russian Federation. We do not believe that it sets any new standards or norms or helps develop common international law.” Or consider consistent opposition to the TPNW shown by Japan, as expressed by its senior government officials. As the TPNW neared entry into force, the North Atlantic Council issued its own statement in which NATO member States collectively reiterated their “opposition to this treaty, as it does not reflect the increasingly challenging international security environment and is at odds with the existing non-proliferation and disarmament architecture.”

Worth noting is an interpretation of such “preemptive persistent objections.” As some have observed,

The fact that the nuclear-armed states feel obliged to denounce the existence of a customary norm against the use and possession of nuclear weapons is, if nothing else, a testament to the relevance of the TPNW. It would have been pointless to declare the non-existence of such a customary norm if it were obvious to everyone that the TPNW could not have an impact on how states interpret the legality of nuclear weapons.

Along with vocal “persistent objectors,” there is a group of States that may be defined as “implicit objectors.” They include States, other than NATO members, that are bound by security arrangements with a nuclear-weapon State (Australia, Republic of Korea) and, presumably, the States that declared their aspirations to join NATO (Georgia and Ukraine). Finland and Sweden, their pro-arms control posture notwithstanding, did not demonstrate their intention to accede to TPNW even prior to their application to join NATO.

It is not evident why members of a Russia-led Collective Security Treaty Organization, except Kazakhstan known for its consistent nuclear abolitionism, are not joining the TPNW, but the very fact that one out of its five members was free to become a party may indicate that the group is tolerant to independent pursuit of vital interests. Kazakhstan, and Japan for that matter, are “specially affected states” by virtue of nuclear energy having been uncontrollably released, whether by way of the use of nuclear weapons in anger or by way of nuclear weapons testing. Other such States are Belarus and Ukraine – both severely affected by the Chernobyl nuclear accident, and again Japan (Fukushima Daiichi nuclear power plant explosion), as well as Algeria, Australia, and the Marshall Islands where nuclear weapons had been tested by third parties. None is a party to the TPNW, although Algeria participated in the negotiating conference, voted for the adoption of the TPNW, and was one of the first fifty to sign it, on 20 September 2017.

Of those, the Republic of the Marshall Islands represents an exceptional, if only symbolic, case. In 2014, the tiny island nation filed applications with the ICJ against nine States with proven nuclear-weapon capability, accusing them of not fulfilling their obligations with respect to the cessation and reversal of the nuclear arms race. The action, eventually brought against only three respondents (Marshall Islands v. India, Marshall Islands v. Pakistan, Marshall Islands v. United Kingdom) failed,  but in its aftermath the Marshall Islands has built up a reputation as a proponent of nuclear disarmament, which it has failed to live up to, being bound by security arrangements with a nuclear-weapon State.

Nuclear-weapon States, whether formally recognized as such or not, and States that are covered by security arrangements with nuclear-weapon States, should also qualify as “specially affected.” Presumably, the notion of “specially affected states” may also apply to States Parties to nuclear-weapon-free-zone treaties, meaning dedicated treaties applicable to sovereign territories, as opposed to the Antarctic Treaty. Here, the statistics so far do not seem extremely favorable to champions of the TPNW.

Take the oldest such zone established by the Treaty for the Prohibition of Nuclear Weapons in Latin America and the Caribbean of 1967 – of the 33 parties, 25 have ratified the TPNW; 3, including Brazil, have only signed it; and 5, including Argentina, have not even signed. Incidentally, Argentina and Brazil, both regional heavy-weights, voted for the adoption of the TPNW. Or consider the zone most recently established by the Treaty on a Nuclear-Weapon-Free Zone in Central Asia (in force since 2009) – only one out of five Parties, Kazakhstan, ratified the TPNW.

Of course, these numbers may change with time. Besides, as stated by one of the characters of Arthur Hailey’s novel The Moneychangers, “statistics could be used to prove anything.”[ii] And yet those numbers and the States behind them may serve as evidence of dwindling enthusiasm for the TPNW and the means that its drafters chose to pursue its declared object and purpose.


At a Panel on the TPNW which was part of the 79th (Kyoto) Conference of the International Law Association, held online on 8 December 2020, a panelist lamented lack of “a modicum of honesty in relation to nuclear weapons from the opponents of the Treaty.” The preceding remarks are not intended to put into doubt the sincere desire of champions of the TPNW to rid the world of nuclear weapons, if only embodied in a legal text which is not always a model of exemplary treaty draftsmanship. The TPNW is also a reflection of dissatisfaction with the absence of progress in nuclear arms control negotiations. However, nuclear weapons are here to stay, hopefully as a deterrent, rather than a fighting tool. They will continue to exist amid legal and political permissions, restrictions, and prohibitions. A goal with a modicum of realism would be to make permissions shrink while expanding restrictions and prohibitions, but not at the expense, and to the detriment, of existing or nascent regulatory regimes, such as the NPT, the CTBT, regional nuclear-weapon-free zones, as well as non-treaty regimes designed to prevent proliferation of nuclear weapon technologies, fissile materials, or delivery systems.


Bakhtiyar Tuzmukhamedov is Professor of International Law, Vice-President of the Russian Association of International Law, Vice-Chairperson of the Committee against Torture, member of the Council of the International Institute of Humanitarian Law, and a member of the editorial boards of the Russian Yearbook of International Law and the International Review of the Red Cross.


Photo credit: Pexels, Pixabay

[i] For an insightful and balanced critique of imperfections of the TPNW, see Dieter Fleck, “The Treaty on the Prohibition of Nuclear Weapons: Challenges for International Law and Security,” in IV Nuclear Non-Proliferation in International Law 395-415 (Jonathan L. Black & Dieter Fleck eds., T.M.C. Asser Press, The Hauge, 2019).

[ii] Arthur Hailey, The Moneychangers 281 (Bantam Books, 20th prtg. 1976).