Article I consists of two paragraphs that set forth the basic obligations of the States Parties to the Treaty. The Article requires each State Party: not to carry out any nuclear weapon test explosion or any other nuclear explosion; to prohibit and prevent any such nuclear explosion at any place under its jurisdiction or control; 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.

The text of Article I is based on, and similar to, Article I of the LTBT, which entered into force on October 10, 1963.

In paragraph 1 of Article I, each State Party undertakes, inter alia, not to "carry out any nuclear weapon test explosion or any other nuclear explosion." This means that each State Party to the Treaty is prohibited from carrying out a nuclear weapon test explosion or any other nuclear explosion anywhere in any environment, including underground. Thus, the Treaty completes the task that was begun in the LTBT, which prohibits nuclear weapon test explosions and any other nuclear explosions in three environments but does not prohibit underground nuclear explosions.

During the negotiation of the Treaty, the question arose whether it was necessary to state in the text that the obligation not to carry out any nuclear weapon test explosion or any other nuclear explosion extended to all environments or to enumerate the all-inclusive four environments to which the obligation applies, i.e., in the atmosphere, in outer space, underwater, and underground. By not specifying the environments in Article I, the Treaty avoids any confusion about possible loopholes. The prohibition on carrying out a nuclear weapon test explosion or any other nuclear explosion applies universally.

Nuclear Explosions for Peaceful Purposes

During the negotiation of the LTBT, the phrase "or any other nuclear explosion" was included for the specific purpose of prohibiting explosions of nuclear devices for peaceful applications, so-called "peaceful nuclear explosions" or "PNEs." LTBT negotiators recognized that any nuclear explosion could provide military benefits, and therefore that without the inclusion of this phrase, a State Party could conduct nuclear explosions providing valuable military benefits on the pretense that they were solely peaceful purposes explosions and not "nuclear weapon test explosions."

During much of the negotiation of the Treaty, one delegation in particular, China, sought to retain the possibility of carrying out underground nuclear explosions for peaceful purposes, citing Article V of the NPT, which recognizes that, for reasons of non-discrimination, non-military benefits that might be derived from peaceful applications of nuclear explosions would need to be available to non-nuclear weapon States Parties.

All delegations, after careful consideration, ultimately accepted the inclusion of the phrase "or any other nuclear explosion" in Article I of the Treaty, recognizing that PNEs would be prohibited. However, it is relevant to note that language was inserted into paragraph 1 of Article VIII providing that the first Review Conference, if any State Party so requests, may consider the possibility of permitting the conduct of underground nuclear explosions for peaceful purposes. If the Review Conference decides by consensus that such nuclear explosions may be permitted, it may recommend to States Parties an appropriate amendment that would preclude any military benefits of such nuclear explosions. Any such proposed amendment would require consensus approval for adoption, and would not enter into force until ratified by those States Parties that voted for the amendment, in accordance with the provisions of Article VII. Thus, the Treaty could not be amended to permit the conduct of underground nuclear explosions for peaceful purposes without the approval of the United States.

Activities Not Affected By The Treaty

The U.S. decided at the outset of negotiations that it was unnecessary, and probably would be problematic, to seek to include a definition in the Treaty text of a "nuclear weapon test explosion or any other nuclear explosion" for the purpose of specifying in technical terms what is prohibited by the Treaty. It is important to emphasize that Article I prohibits only nuclear explosions, not all activities involving a release of nuclear energy. It is clearly understood by all negotiating parties, as a result of President Clinton's announcement on August 11, 1995, that the U.S. will continue to conduct a range of nuclear weapon-related activities to ensure the safety and reliability of its nuclear weapons stockpile, some of which, while not involving a nuclear explosion, may result in the release of nuclear energy. Such activities, a number of which are planned as part of the Stockpile Stewardship and Management Program (SSMP), could include: computer modeling; experiments using fast burst or pulse reactors; experiments using pulse power facilities; inertial confinement fusion (ICF) and similar experiments; property research of materials, including high explosives and fissile materials, and hydrodynamic experiments, including subcritical experiments involving fissile material. None of these activities will constitute a nuclear explosion. Similarly, activities related to the operation of nuclear power and research reactors and the operation of accelerators are not prohibited pursuant to Article I, despite the fact that such activities may result in the release of nuclear energy. The examples of activities not prohibited by the Treaty cited above are not all-inclusive, but are illustrative.

Concerning ICF, the U.S. statement made at the 1975 NPT Review Conference established that energy sources "involving nuclear reactions initiated in millimeter-sized pellets of fissionable and/or fusionable material by lasers or by energetic beams of particles, in which the energy releases, while extremely rapid, are designed to be and will be non-destructively contained within a suitable vessel" do not constitute "a nuclear explosive device within the meaning of the NPT or undertakings in IAEA safeguards agreements against diversion to any nuclear explosive device." Thus, such energy releases at the planned National Ignition Facility, as well as at existing facilities such as the NOVA laser facility, are not considered nuclear explosions and are not prohibited by the Treaty.

With respect to the obligation "not to carry out" any nuclear explosion, the negotiating record reveals that Article I does not limit in any way a State Party's ability to conduct activities in preparation for a nuclear weapon test explosion or any other nuclear explosion. During the negotiations, a proposal to prohibit such preparations was rejected as being unnecessary, too difficult to define, and too complicated and costly to verify. In addition, the U.S. opposed this proposal because it might interfere with its ability to maintain the basic capability to resume nuclear test activities prohibited by the Treaty should the United States exercise its "supreme interests" rights pursuant to Article IX and withdraw from the Treaty - one of the Treaty Safeguards announced by the White House on August 11, 1995.

Although preparations would not constitute non-compliance, a State Party could use the consultation and clarification procedures set forth in Article IV to address concerns about such preparations. In addition, irrespective of the CTBT, any state with information regarding another state's preparations to conduct a nuclear explosion could bring the matter directly to the attention of the UN Security Council.

The United States understands that Article I, paragraph 1 does not prohibit any activities not involving nuclear explosions that are required to maintain the safety, security, and reliability of the U.S. nuclear stockpile, to include: design, development, production, and remanufacture of nuclear weapons, replacement of weapon parts, flight testing of weapon components, engineering tests of the mechanical and electrical integrity of weapon components under a variety of environmental conditions, and changes to weapons. The United States also understands that the CTBT does not prohibit disposal or rendering safe of damaged weapons and terrorist devices, and experiments not involving nuclear explosions to develop render-safe methods.

Finally, the obligation "not to carry out any nuclear weapon test explosion or any other nuclear explosion" does not place limitations on the ability of the United States to use nuclear weapons. As noted above, the phrase "or any other nuclear explosion" is identical in meaning to that of the same text in the LTBT, where it was clearly understood that the phrase would not apply to a prohibition of the use of nuclear weapons in the event of war. Similarly, the CTBT negotiating record demonstrates that the prohibitions in Article I do not apply to the use of nuclear weapons. The U.S. position, which was repeated on numerous occasions, was that any proposed undertakings relating to the use of nuclear weapons were totally beyond the scope of this Treaty and the mandate for its negotiation. Moreover, the Preamble reflects this view in that it does not in any way address the issue of the use of nuclear weapons. Thus, Article I of the Treaty cannot be deemed to prohibit the use of nuclear weapons or restrict the exercise of the right of self-defense recognized in Article 51 of the Charter of the United Nations.

Obligation to "Prohibit and Prevent"

Paragraph 1 of Article I also obligates each State Party to prohibit and prevent any nuclear weapon test explosion or any other nuclear explosion at any place under its jurisdiction or control. This provision represents an evolution of the LTBT formulation in that it separates the obligation not to carry out" from the obligation to "prohibit and prevent." CTBT negotiators adopted this formulation in order to make clear that the obligation "not to carry out" is an unqualified ban on activities of the State Party, while the requirement to "prohibit and prevent" is directed at activities of other states and of non-state entities that are conducted on the territory of the State Party or at places under its jurisdiction or control.

Delegations recognized that it would be difficult, if not impossible, for a State Party to accept an obligation not only to prohibit, but to prevent any nuclear weapon test explosion or any other nuclear explosion in a place beyond its jurisdiction and control. Examples of places beyond the jurisdiction or control of a State Party include the high seas and, with certain exceptions, the territory of another state. Because a State Party might not be able to prevent a nuclear explosion conducted by another state or entity from occurring in such places, each State Party's obligation to "prohibit and prevent" any nuclear weapon test explosion and any other nuclear explosion is limited to places over which it has jurisdiction or control.

Obligation not to "Cause, Encourage, or Participate In"

In paragraph 2 of Article I, each State Party undertakes 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. This provision, drawn from the LTBT, prevents a State Party from doing indirectly what it has agreed to refrain from doing directly. For example, a State Party may not provide a corporation with the money and technology necessary to carry out a nuclear explosion on its behalf. Note that, although the Article I obligation to "prohibit and prevent" extends only to places under a State Party's jurisdiction or control, as discussed above, a State Party would be in violation of Article I if it were established that it had caused, encouraged, or participated in a nuclear explosion, even though the explosion may have occurred in a place not under the jurisdiction or control of the State Party and was carried out by another state or non-state entity.