The Treaty on the Prohibition of Nuclear Weapons

Treasa Dunworth
October 31, 2017


On October 6, 2017, the International Campaign to Abolish Nuclear Weapons (ICAN) was awarded the Nobel Peace Prize. In its announcement, the Nobel Peace Prize Committee stated that ICAN was receiving the award because of its “ground-breaking efforts to achieve a treaty-based prohibition of such weapons.” The Committee was referring to the Treaty on the Prohibition of Nuclear Weapons (TPNW) which was adopted at the United Nations in July 2017. The treaty has considerable, but not universal, support. Hailed by some as “an important step towards the universally-held goal of a world free of nuclear weapons,”[1] others see it as a treaty that “risks undermining the existing international security architecture.”[2]

This Insight explains the background to the treaty, provides an overview of its key provisions, and explains why it is a significant international legal development, notwithstanding the lack of universal acclaim.

Background to the Treaty

The legal roots of this treaty go back to Article 6 of the Nuclear Non-Proliferation Treaty of 1968 (NPT), in which parties undertook “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 NPT’s objective was to stop the spread of nuclear weapons, and given that there are only nine nuclear-weapon states in the world today, and nearly all states in the world are party to the NPT, it not surprising that it is generally considered the “cornerstone” of the nuclear nonproliferation legal framework.[3]

The parties to the NPT have repeatedly affirmed the legal obligation in Article 6. In 1995, in agreeing to extend the treaty beyond its initial twenty-five-year term, the Conference of the Parties affirmed the need for attaining “the ultimate goals of the complete elimination of nuclear weapons and a treaty on general and complete disarmament under strict and effective control.”[4] In 2000, they agreed to thirteen practical steps for systematic and progressive efforts towards disarmament.[5] In 2010, they affirmed the obligation that all states have “to make special efforts to establish the necessary framework to achieve and maintain a world without nuclear weapons.”[6]

The International Court of Justice has also noted the binding obligation to pursue nuclear disarmament. In a unanimous finding in its Nuclear Weapons Advisory Opinion, all fifteen judges opined that there exists an “obligation to pursue in good faith and bring to a conclusion negotiations leading to nuclear disarmament in all its aspects under strict and effective international control.”[7]

The apparent consensus on the legal obligation to pursue nuclear weapons disarmament has not been reflected in practice. Despite the efforts of many states over many decades in the UN General Assembly and in the Conference on Disarmament, it was not possible to engage in any meaningful way in nuclear disarmament talks. However, a shift in state opinion occurred in 2013 when a series of three conferences were convened to explore the humanitarian consequences of a nuclear detonation.[8] Those discussions highlighted that a nuclear war would be catastrophic with no possibility of any meaningful humanitarian response. This led to renewed momentum in the General Assembly, which in turn led to Assembly-mandated negotiations. Those negotiations concluded on July 7, 2017, when 122 states voted in favor of adopting the Treaty on the Prohibition of Nuclear Weapons.[9] It opened for signature on September 20, 2017, and will enter into force following fifty ratifications.[10] At the time of writing, fifty-three states have signed the treaty, with three of those states also having ratified the treaty.[11]

An Overview of the Key Provisions

The treaty bans the use, threat of use, production, manufacturing, testing, possession, stockpiling, stationing, and transfer of nuclear weapons.[12] Reflecting the humanitarian concerns of its founding states, the treaty has a number of cooperation and assistance provisions, including on victim assistance.[13] Of particular note is an obligation on parties to take environmental remediation measures in respect of areas that have been contaminated by the testing or use of nuclear weapons.[14]

The treaty acknowledges the possibility that states currently possessing nuclear weapons may wish to join the treaty at some point in the future, and as such, Article 4 provides a roadmap for this to happen, including providing for the involvement of the International Atomic Energy Agency, which also has a role in verifying compliance with the NPT.[15]

While it does not create a standing secretariat to oversee implementation, states are required to file declarations with the United Nations, and there are procedures in place for meetings of the states parties and for Review Conferences to oversee the implementation of the treaty. Article 11 deals with dispute settlement, exhorting states to settle any disputes peacefully, as is required by the UN Charter in any event.

The Legal Impact of the Treaty

There are nine states in the world today that possess nuclear weapons—China, the Democratic People’s Republic of Korea, France, India, Israel, Pakistan, the Russian Federation, the United Kingdom, and the United States of America—none of which participated in the negotiations. They are not alone in their opposition. They are joined by all the NATO allies as well as Australia, South Korea, and Japan, which are also in security relationships with the United States.

These possessor states and their allies make two core legal arguments opposing the treaty. First, it risks undermining the NPT, which, as the “cornerstone” of the nuclear weapons legal architecture, they say must be protected. Second, the treaty cannot have any normative impact in any event because it has been negotiated without input from the nuclear possessor states and will not be ratified by any of them.

Basic international legal analysis does not support either argument.

The Treaty Will Not Undermine the NPT

The treaty will not undermine the NPT, rather it will complement it. When two treaties deal with overlapping subject matter, the Vienna Convention on the Law of Treaties 1969 (VCLT) provides that when the parties to a later treaty do not include all the parties to the earlier treaty, the later treaty does not affect or disrupt the existing treaty relationships for states not joining the new treaty.[16] Thus, in this case, the TPNW cannot supplant the rights and obligations of those parties to the NPT that choose to remain outside the new treaty. For NPT parties that do join the TPNW, their obligations (such as the prohibitions on testing, possessing, using, transferring or stationing of nuclear weapons) complement rather than undermine the NPT because all those obligations are either explicitly or implicitly provided for in the NPT itself already.[17]

The need to ensure that the NPT was not in any way undermined was an important issue for negotiating states. Thus, Article 18 TPNW provides that its implementation “shall not prejudice obligations undertaken by States Parties with regard to existing international agreements, to which they are a party, where those obligations are consistent with the Treaty.”

Can the Treaty have Normative Effect with this Level of Opposition?

In awarding this year’s Nobel Peace Prize, the Norwegian Nobel Committee stated that it was “aware that an international legal prohibition will not in itself eliminate a single nuclear weapon.” That may be true, but it is also the case that practice indicates that normative development is possible even without engagement by specially affected states.[18] Treaties can, and do, shift international expectations and result in policy change over time, even within states that have chosen to remain outside a particular regime. For example, in the context of chemical weapons, the 1925 Geneva Protocol is very widely accepted as an important part of the development of the “chemical weapons taboo” and in fact it was cited by many as constituting a “constraining influence” that prevented widespread use of chemical weapons during the Second World War.[19]  This was despite the absence of the United States from the treaty. But it also laid the foundations for the Chemical Weapons Convention 1993, which instituted a comprehensive verifiable ban on chemical weapons.

The Landmines Convention provides another example. Today, there are 162 states parties, but many states, including the main producers and many users of landmines remain formally outside the regime. Nevertheless, some of those states have imposed moratoria on exports, including China, India, Israel, Pakistan, Russia, South Korea, and the United States. Further, while the United States remains a non-party, President George W. Bush announced in 2004 that the United States would eliminate all forms of “persistent” mines.[20] In January 2011, all persistent mines were withdrawn from active inventories.[21] Then, in June 2014, the United States announced that it would not produce or otherwise acquire any antipersonnel landmines in the future, including to replace existing stockpiles.[22] Similarly, China remains outside the treaty, but attends its Meetings of States Parties and has not deployed landmines in the past decade.

Thus, we see that perceptions of security interests and the legitimacy of particular weapons can and do evolve. It is difficult to demonstrate absolutely the influence of widely supported but not universal agreements. But the evidence does suggest that, even in the absence of engagement by the most powerful states at the outset, such agreements can have a very significant impact over time on the evolution of international norms against weapons and lead progressively to their eventual elimination. The same may well hold true for nuclear weapons.


In making the award to ICAN, the Nobel Peace Prize Committee stated that the prize was also a call upon the nuclear possessor states “to initiate serious negotiations with a view to the gradual, balanced and carefully monitored elimination of the almost 15,000 nuclear weapons in the world."[23]

Admittedly, prospects are not encouraging at the moment, in light of the modernization programs in the United Kingdom, the United States, and France, along with China’s planned expansion of its nuclear weapons program. However, it is very early days and the TPNW may yet have normative effect. Meanwhile, it has certainly provided the opportunity for the vast majority of states in the world—the non-possessor states—to affirm their own commitment to a nuclear weapons free world.

About the Author: Treasa Dunworth is an Associate Professor, Faculty of Law, University of Auckland, New Zealand.

[1] The Secretary-General’s Remarks at Signing Ceremony for the Treaty on the Prohibition of Nuclear Weapons [as delivered], UN Secretary General (Sept. 20, 2017),

[2] Joint Press Statement from the Permanent Representatives to the United Nations of the United States, United Kingdom, and France Following the Adoption of a Treaty Banning Nuclear Weapons, U.S. Mission to the UN (July 7, 2017),

[3] The only states not party to the NPT are the Democratic People’s Republic of Korea, India, Israel, Pakistan, and South Sudan.

[4] Review and Extension Conference of the Parties to the Treaty on the Non-Proliferation of Nuclear Weapons, Final Document U.N. Doc. NPT/CONF.1995/32 (Part I), annex, Decision 3 (May 5, 1995).

[5] Review Conference of the Parties to the Treaty on the Non-Proliferation of Nuclear Weapons, Final Document, U.N. Doc. NPT/CONF.2000/28 (Parts I and II), 13–15 (May 19, 2000).

[6] Review Conference of the Parties to the Treaty on the Non-Proliferation of Nuclear Weapons, Final Document, U.N. Doc. NPT/CONF.2010/50 (Vol I), 20 (June 18, 2010).

[7] Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, 1996 I.C.J. Rep. 226, ¶ 105(2)(f) (July 8).

[8] In Oslo (March 2013), in Mexico (February 2014) and in Austria (December 2014).

[9] One state voted against (the Netherlands) and one state abstained (Singapore).

[10] Treaty on the Prohibition of Nuclear Weapons art 15(1), Sept. 20, 2017, U.N. Doc. A/CONF.229/2017/L.3/Rev.1 [hereinafter TPNW].

[11] Guyana, Holy See, and Thailand.

[12] TPNW, supra note 10, art 1.

[13] Id. arts. 6 & 7.

[14] Id. art. 6(2).

[15] Id. art. 4.

[16] Vienna Convention on the Law of Treaties 1969 arts 30, 59, May 23, 1969, 1155 U.N.T.S. 331. A good example of how this works in practice is provided by Article XIII of the Chemical Weapons Convention of 1993, which provides that nothing in that treaty shall be interpreted as in any way limiting or detracting from the obligations earlier assumed by any state under either the 1925 Geneva Protocol or the 1972 Biological Weapons Convention.  

[17] This point is elaborated in detail in Treasa Dunworth, Strengthening the NPT: International Law and Effective Measures for Nuclear Disarmament, (Faculty of Law, University of Auckland, Discussion Paper, Oct. 2015), available at

[18] Adam Bower, Norms without the Great Powers: International Law, Nested Social Structures, and the Ban on Antipersonnel Mines, 17 Int’l Studies Rev., 347, 349 (2015).

[19] Richard Price, A Genealogy of the Chemical Weapons Taboo, 49 Int’l Org. 73–103 (1995).

[20] That is, mines that do not contain a self-deactivating device.

[21] Bower, supra note 18, n.21, 22.

[22] Statement by Ambassador Griffiths, United States Embassy, Maputo, to the Third Review Conference to the Convention on the Prohibition of the Use, Stockpiling, Production and Transfer of Anti-Personnel Mines and on their Destruction (June 27, 2014).

[23] Nobel Peace Prize Committee Statement, Nobel Prize (Oct. 25, 2017),