5.01  Article 5 concerns the general duty to implement the Treaty on the Prohibition of Nuclear Weapons¹ (2017 Treaty) at national level. The ‘necessary’ measures must be ‘adopted’ domestically to implement a state party’s positive obligations, while ‘all appropriate’ measures, including the imposition of penal sanctions, must be taken to ‘prevent and suppress’ any prohibited activity, where it is undertaken by persons or on territory under a state party’s jurisdiction or control.

5.02  The text of this article was amended only slightly during the negotiations. In the first draft of 22 May 2017, Article 7 on national implementation stipulated as follows:

1. 1.  Each State Party shall, in accordance with its constitutional processes, adopt the necessary measures to implement its obligations under this Convention.

2. 2.  Each State Party shall take all appropriate legal, administrative and other measures, including the imposition of penal sanctions, to prevent and suppress any activity prohibited to a State Party under this Convention undertaken by persons or on territory under its jurisdiction or control.

(p. 203) Paragraph 1 reflected verbatim the text of Article VII(1) of the 1992 Chemical Weapons Convention,² while paragraph 2 repeated the wording of Article 9 of the 1997 Anti-Personnel Mine Ban Convention.³

5.03  In discussions in plenary on the proposed text at the Second Session of the UN Diplomatic Conference, Ireland, supported by Argentina, Ecuador, and Singapore, called for the deletion of the words ‘in accordance with its constitutional processes’.⁴ Ireland also proposed adding the word ‘prohibit’ in the second paragraph before ‘prevent and suppress’, but this was not accepted. Iran unsuccessfully called for the replacement of the words ‘necessary measures’ with ‘any appropriate measures’.⁵ The Netherlands advocated deleting the reference to ‘legal’ measures.⁶ New Zealand suggested merging the two paragraphs but this was similarly not accepted.⁷

5.04  The text in the draft of 27 June remained unchanged as it did in the facilitator’s text of 30 June,⁸ even though in the plenary discussion on the text Brazil, referring to Article 27 of the 1969 Vienna Convention on the Law of Treaties, echoed earlier calls for the deletion of the words ‘in accordance with its constitutional processes’.⁹ Austria and South Africa supported Brazil, although Iran was ‘not sure’ it could endorse such a deletion, noting that the phrase was included in similar provisions in the 1992 Chemical Weapons Convention, the 1996 Comprehensive Nuclear-Test-Ban Treaty (CTBT),¹⁰ and the 1966 International Covenant on Civil and Political Rights.¹¹ In the comprehensive treaty draft of 3 July the words had been removed.¹² With only a small typographical correction (the deletion of the floating comma in paragraph 1), this would become the text in the 2017 Treaty:

5.05  Paragraph 1 can be seen as the reflection of two general rules of the law of treaties. The first, known by its brocard, pacta sunt servanda, holds that: ‘Every treaty in force is binding upon the parties to it and must be performed by them in good faith.’¹³ The second rule stipulates that a party to a treaty ‘may not invoke the provisions of its internal law as justification for its failure to perform a treaty’.¹⁴ It could thus be argued that the text in paragraph 1 adds little to a state party’s existing duties under international law to perform its treaty obligations in good faith, but its inclusion is valuable.

5.06  In terms of ‘necessary measures’, among other such measures a state party must, in addition to respecting and ensuring respect for the prohibitions in Article 1, provide the UN Secretary-General with the declaration required by Article 2 in due time; fulfil all disarmament and related reporting requirements under Articles 3 and 4; provide adequate assistance to the victims of nuclear weapons testing or use and carry out environmental remediation of affected areas (obligations detailed in Article 6); cooperate with other states parties to facilitate the implementation of the 2017 Treaty (Article 7); meet its share of the costs of the Treaty (Article 9); and encourage states not party to the Treaty to adhere to it.

5.07  Paragraph 2 does, as New Zealand observed during plenary discussions at the Second Session of the UN Diplomatic Conference, overlap with the previous paragraph. Here, however, the focus is on domestic criminalisation of prohibited acts, especially those set out in Article 1. Of particular importance will be the establishment of a criminal offence for assisting anyone in any way to develop, test, produce, stockpile, or transfer nuclear weapons or other nuclear explosive devices.

5.08  The obligation to take ‘all appropriate legal, administrative and other measures, including the imposition of penal sanctions, to prevent and suppress’ prohibited activity does not explicitly require new legislation. It may well be that a state party already prohibits these activities directly or indirectly in its national law. In a monist state, the treaty might be regarded as self-executing.¹⁵ But if any of the acts prohibited under Article 1 are somehow lawful when committed by all or certain individuals falling under a domestic legal regime, it will surely be ‘appropriate’ to remedy this lacuna.

5.09  Legal measures include not only statutes adopted by the legislative element of the state (typically a parliament) but also implementing ordinances or regulations and cabinet or presidential decrees. In terms of sentences for violations, a wide margin of discretion will be accorded to each state party. That said, grossly excessive or manifestly inadequate penalties for serious violations of the 2017 Treaty, such as for transfer or use of a nuclear (p. 205) explosive device, will not meet a state party’s duty of good faith in the implementation of its international legal obligations at domestic level.

5.10  Administrative measures would include such acts as instructions to members of the armed forces, revision of military manuals and doctrine, and associated training. In case of states parties hosting foreign nuclear explosive devices on their territory, there would need to be discussions with the foreign ally to enable the state party to comply with its obligations to ensure the ‘prompt removal’ of the devices from ‘any place under its jurisdiction or control’.¹⁶

5.11  The scope of the jurisdiction required by the 2017 Treaty, particularly for the criminal law, is set out in the phrase ‘undertaken by persons or on territory under its jurisdiction or control’. As noted, this repeats wording verbatim from the 1997 Anti-Personnel Mine Ban Convention. The clause combines the duty to exercise personal jurisdiction with territorial jurisdiction.

5.12  The wording of paragraph 2 does not make it explicit whether the term ‘person’ is to encompass legal persons as well as natural persons (i.e. individuals).¹⁷ However, given the breadth of the undertaking in Article 1(1)(e) of the 2017 Treaty, which prohibits assisting, encouraging, or inciting ‘anyone’ to engage in prohibited conduct,¹⁸ and the fact that the term ‘person’ in paragraph 2 of Article 5 is not limited to natural persons, it should apply also to legal persons.

5.13  A legal person primarily means a public or private company, though it may also in certain circumstances encompass an international organisation. Here, though, the wording is effectively limited to persons under the state party’s jurisdiction or control, which could exclude international organisations from coverage. A company, which applies to ‘any business entity that conducts a value exchange of goods or services with customers’,¹⁹ includes, but is not limited to, a corporation. Countries generally allow for civil liability for companies; today many, but not all, also provide for criminal liability. This is, though, ‘a relatively recent legal development, becoming more prevalent over the last 100 years or so’.²⁰ This suggests a margin of discretion might exist in this regard for states parties.

5.14  The question also arises as to whether jurisdiction must be exercised extraterritorially. Again, the duty to ensure respect for several provisions in Article 1 by ‘any recipient whatsoever’²¹ ‘in any way’,²² ‘directly or indirectly’,²³ strongly implies that a natural or legal (p. 206) person should be restrained by relevant legislation when a national, or a company registered within the state party’s jurisdiction, acts beyond the state party’s territory.

5.15  Under international law, jurisdiction is primarily territorial.²⁴ A state has primary jurisdiction over all of its sovereign territory, which includes not just land mass but also the airspace above that land and the territorial seas (typically extending 12 nautical miles from the coastal baseline).²⁵ Jurisdiction also applies to vessels that fly the flag of the state on the high seas or in the air, and to a state’s foreign embassies.²⁶ The notion of control refers primarily to foreign territory that is occupied by the state party but which is not part of a state’s sovereign territory. The formulation ‘in its territory or at any place under its jurisdiction or control’, found in, inter alia, Article 1(1)(g), equates directly to the language in paragraph 2: ‘on territory under … [a state party’s] jurisdiction or control’.

5.16  Thus, in accordance with paragraph 2, a state party must apply all appropriate measures, including national laws, to any sovereign territory, whether that is metropolitan or non-metropolitan, as well as to any other territory it controls. Of course, the prohibitions set out in Article 1 would apply more broadly to any area on the earth or in space.