Article III consists of four paragraphs, which set forth the obligations of States Parties with regard to their domestic implementation of the Treaty and their relationships with other States Parties and the Organization.

Paragraph 1 of Article III, in three subparagraphs, requires each State Party, in accordance with its constitutional processes, to take any measures that are necessary in order for it to carry out its obligations under the Treaty and in particular to prohibit natural and legal persons from engaging in activities prohibited to a State Party. The purpose of Paragraph 1 is to extend the prohibitions on activities by States Parties, primarily the Article I obligations not to carry out any nuclear weapon test explosion or any other nuclear explosion, and to refrain from causing, encouraging or in any way participating in the carrying out of any nuclear weapon test explosion or any other nuclear explosion, to private individuals and "legal persons" such as corporations.

Subparagraph 1(a) of Article III requires each State Party to prohibit natural and legal persons anywhere on its territory or in any other place under its jurisdiction as recognized by international law from undertaking any activity prohibited to a State Party under the Treaty. Thus, this subparagraph governs the activities of private individuals and corporations, regardless of their nationality, (a) on a State Party's territory, or (b) anywhere outside its territory that is nevertheless under its jurisdiction, e.g., on ships or aircraft flying its flag.

Subparagraph (a) does not specifically require States Parties to enact penal legislation when implementing this obligation. Negotiators reached an understanding that subparagraph (a) required each State Party to impose penalties, whether criminal, civil or administrative, on natural and legal persons who engage in prohibited activities, using the most appropriate legal mechanisms available to that State Party under its domestic legal system.

Subparagraph 1(b) of Article III requires each State Party to prohibit natural and legal persons from undertaking any activity prohibited to a State Party under this Treaty anywhere under its control. This subparagraph thus governs the activities of private individuals and corporations, regardless of their nationality, in places under the State Party's control whether or not under its jurisdiction.

Subparagraphs 1(a) and (b) must be read in conjunction with paragraph 1 of Article I, which requires, inter alia, each State Party to "prohibit and prevent" any nuclear explosion at any place under its jurisdiction or control. Thus, while a State Party might fulfill its paragraph 1(a) and (b) obligations by prohibiting such activities through domestic legislation, Presidential decree, regulations or otherwise, that state must also take affirmative action where necessary to enforce the prohibition against carrying out any nuclear explosion on its territory or in any other place under its jurisdiction or control, in order to comply with its Article I obligation to prevent such activities from occurring. Note, however, that a violation of Article I, paragraph 1 would not occur until a nuclear weapon test explosion or other nuclear explosion actually took place.

Subparagraph 1(c) of Article III requires each State Party to prohibit, in conformity with international law, any activity prohibited to a State Party under the Treaty undertaken anywhere by natural persons who possess its nationality. This means that each State Party must extend its prohibitions to include activities conducted by its citizens outside its territory or other places under its jurisdiction. Note that this requirement to prohibit does not extend extra-territorially to corporations.

Note also that for individuals, effective implementation of this subparagraph would require each State Party to carry out enforcement actions with regard to its citizens for activities conducted by such citizens outside its territory or other places under its jurisdiction, when such citizens are present in its territory.

Paragraph 2 of Article III requires States Parties to cooperate with each other and to accord the appropriate form of legal assistance to facilitate the implementation of the obligations under paragraph 1. The purpose of this paragraph is to require States Parties to work together on the enforcement of their domestic prohibitions on the activities of private individuals and corporations.

Paragraph 3 of Article III requires each State Party to inform the Organization of the legislation it has enacted, Presidential decrees or orders it has issued or other measures taken to implement this Article.

Paragraph 4 of Article III requires each State Party to designate or set up a National Authority to serve as the national focal point for liaison with the Organization and other States Parties and to notify the Organization of its National Authority when the Treaty enters into force for it. The purpose of this paragraph is to facilitate the interaction between a State Party and the Organization or other States Parties regarding implementation of the Treaty, particularly exchanging IMS data and conducting inspections, by ensuring that each State Party will have a central point of contact for such activities.