The Relationship of the 2017 Treaty on the Prohibition of Nuclear Weapons with other Agreements: Ambiguity, Complementarity, or Conflict?

As discussed in Dan Joyner’s recent blog entry, the Treaty on the Prohibition of Nuclear Weapons was adopted by 122 States at a United Nations diplomatic conference in New York on 7 July 2017. Article 18 of the Treaty addresses its “relationship with other agreements”. There is, though, an ongoing debate as to the implications of this provision. On 7 July 2017, following the adoption of the Treaty by participating states in the United Nations diplomatic conference, Singapore (the sole abstention) stated in its explanation of vote that phrasing in the article was “ambiguous”. In this blog entry, I argue that this claim is unfounded.

Article 18 is based on a corresponding provision in Article 26(1) of the 2013 Arms Trade Treaty (ATT), the intent of which was to ensure that ATT states parties could adopt, or be party to, treaties and other binding agreements governing the trade in conventional arms and ammunition but that they could not lawfully implement any provisions under these other agreements if the obligations therein were inconsistent with their obligations in the ATT.

In the first draft of the Treaty on the Prohibition of Nuclear Weapons (22 May 2017), it was stipulated in Article 19 that it “does not affect the rights and obligations of the States Parties under the Treaty on the Non-Proliferation of Nuclear Weapons”. Thus, it was apparent from the outset that the relationship between the future Treaty and the 1968 Treaty on the Non-Proliferation of Nuclear Weapons (NPT) could be a bone of contention during the negotiations. This was borne out in practice in the June–July 2017 diplomatic conference.

With respect to relevant “obligations”, Article 1(b) and (c) of the Treaty on the Prohibition of Nuclear Weapons, as adopted, is taken verbatim from Articles I and II of the NPT, respectively. In addition, although the precise formulations differ, there are clear prohibitions on assisting any of the prohibited activities in both the NPT and the Treaty on the Prohibition of Nuclear Weapons.

More problematic in the first draft treaty text were the “rights” to which draft Article 19 referred. This could, according to one interpretation, have allowed the five nuclear-weapon states parties to the NPT — China, France, Russia, United Kingdom, and the United States — to adhere to the future Treaty on the Prohibition of Nuclear Weapons while retaining nuclear weapons, a scenario that would have defeated the purpose of the ban treaty, and was therefore unacceptable to the overwhelming majority of participating states in the June–July 2017 diplomatic conference.

Following plenary interventions by numerous states, the draft article was significantly amended to read in the final text of the Treaty as follows:

The implementation of this Treaty shall not prejudice obligations undertaken by States Parties with regard to existing international agreements, to which they are party, where those obligations are consistent with the Treaty.

The key words are “consistent with”. What these words mean in this provision is that obligations upon states parties to the Treaty from other agreements to which they are party and that are less restrictive cannot supersede those set out in the Treaty. In other words, a state party to another (less far-reaching) agreement on nuclear weapons cannot use its adherence to that agreement as an argument, much less a legal basis, to undercut the obligations it accepts by ratifying or acceding to the Treaty on the Prohibition of Nuclear Weapons. Of course, “consistent with” does not imply “identical to”. This is not what the wording is, and it’s not what it means.

In some ways, the provision in Article 18 is little more than a statement of common sense. A state party to 1996 Amended Protocol II to the CCW that was also party to the 1997 Anti-Personnel Mine Ban Convention could not sustain in law the argument that because the Protocol allows the use of certain anti-personnel mines in certain instances, this somehow modified the comprehensive prohibition on use under the 1997 Convention. As we all know, Article 26 of the VCLT stipulates that every treaty in force is binding upon the parties to it and must be performed by them in good faith. And this principle – also known by the Latin maxim pacta sunt servanda – firmly underpins the existence and intent of Article 18 of the Treaty on the Prohibition of Nuclear Weapons.

This provision does not preclude a state party from adhering to any other treaty or binding agreement, such as a bilateral accord, that existed prior to it becoming party to the Treaty on the Prohibition of Nuclear Weapons. But it may only respect and implement the obligations under another treaty or agreement to the extent that these obligations do not act as a form of reservation to its obligations under the Treaty on the Prohibition of Nuclear Weapons (reservations being prohibited by Article 17). A state party to the Treaty could therefore ratify and respect the NPT, the 1963 Partial Test-Ban Treaty, or the 1996 Comprehensive Nuclear Test-Ban Treaty (CTBT). None of these requires action that would contravene the 2017 Treaty. However, Article 18 of the Treaty on the Prohibition of Nuclear Weapons confirms that any of the five nuclear-weapon states under the NPT could not lawfully retain their nuclear weapons if ever they adhere to the Treaty. This is consistent with Article 30 of the VCLT, which concerns the application of successive treaties relating to the same subject matter.

In sum, rather than lending itself to any ambiguity, the wording of Article 18 brings valuable clarity to the interpretation and application of the Treaty on the Prohibition of Nuclear Weapons and the conduct that is required of its states parties. It is a reflection of good practice, common sense, and applicable international law, including the good faith expected of States in the implementation of their treaty obligations. For many future states parties to this Treaty will, rightly and lawfully, be party also to other disarmament or non-proliferation agreements pertaining to nuclear weapons or other nuclear explosive devices. The Treaty augments the existing nuclear disarmament and non-proliferation treaty regime, it does not pull it apart or undermine it. But by adhering to the Treaty on the Prohibition of Nuclear Weapons states are going beyond the obligations they accepted in earlier global treaties and agreements. Those that adhere to this Treaty are renouncing nuclear weapons for good.