Science for democratic action
April 2001

Nuclear Sharing in NATO: Is it Legal?

by Otfried Nassauer 1


Historical evidence indicates that, at the time of negotiating the NPT in the 1960s, many countries did not fully understand what implications nuclear sharing had and/or did not know that NATO interpreted nuclear sharing to be legal under the NPT. According to the current understanding of most non-NATO parties to the NPT, NATO nuclear sharing probably violates Articles I and II of the Treaty.

Article I of the NPT prohibits nuclear weapon states that are parties to the NPT from sharing their weapons with non-nuclear states:

"Each nuclear-weapon State Party to the Treaty undertakes not to transfer to any recipient whatsoever nuclear weapons or other nuclear explosive devices or control over such weapons or explosive devices directly, or indirectly; and not in any way to assist, encourage, or induce any non-nuclear-weapon State to manufacture or otherwise acquire nuclear weapons or other nuclear explosive devices, or control over such weapons or explosive devices."

Article II contains a parallel commitment on the part of non-nuclear states parties not to receive them:

"Each non-nuclear weapon State Party to the Treaty undertakes not to receive the transfer from any transferor whatsoever of nuclear weapons or other nuclear explosive devices or of control over such weapons or explosive devices directly, or indirectly; not to manufacture or otherwise acquire nuclear weapons or other nuclear explosive devices; and not to seek or receive any assistance in the manufacture of nuclear weapons or other nuclear explosive devices."

This is complicated treaty language. I will separate my analysis into four sections. First, I would like to clarify what NATO nuclear sharing means. Second, I will talk about the history of the NPT and nuclear sharing. Third, I will address the European Union and nuclear sharing, which is one question that might come up in the future. Finally, I will conclude with some suggestions on how the problem might be addressed.


The meaning of nuclear sharing

Six non-nuclear NATO countries currently host U.S. nuclear weapons on their territories. Up to 180 freefall bombs of the type B-61, Modification 10 may be deployed in Europe. These are bombs designed to be dropped from aircraft. Some of these bombs are designated for possible use in wartime by non-nuclear NATO members. The air forces of these countries operate so-called dual-capable aircraft, which allow them to drop conventional as well as nuclear bombs. The dual capability of these fighter-bombers allows the militaries of these non-nuclear states to participate in NATO nuclear operations, should the Alliance decide to use nuclear weapons and the U.S. President order their use.

The pilots for these aircraft are provided with training specific to use nuclear weapons. The air force units to which these pilots and aircraft belong have the capability to play a part in NATO nuclear planning, including assigning a target, selecting the yield of the warhead for the target, and planning a specific mission for the use of the bombs.

Under NATO nuclear sharing in times of war, the U.S. would hand control of these nuclear weapons over to the non-nuclear weapon states’ pilots for use with aircraft from non-nuclear weapon states. Once the bomb is loaded aboard, once the correct Permissive Action Link code has been entered by the U.S. soldiers guarding the weapons, and once the aircraft begins its mission, control over the respective weapon(s) has been transferred. That is the operational, technical part of what is called nuclear sharing.

Nuclear sharing has also a political side. All non-nuclear weapon states that are members to the NATO treaty are eligible to participate in NATO’s nuclear-planning and consultation processes. This means they are eligible to participate in drawing up target plans, in discussing the use of nuclear weapons in war time, in consultations on whether NATO should ask the U.S. for the use of nuclear weapons, and in consultations when the NATO nuclear weapon states should decide to use nuclear weapons, whether NATO as a whole would agree to do so. All of these tasks are accomplished in NATO’s Nuclear Planning Group (NPG) and its subsidiary bodies.

NATO nuclear sharing, as far as the technical part is concerned, was described in 1964 by one member of the U.S. National Security Council in what was at that time a highly classified memorandum as meaning that "the non-nuclear NATO-partners in effect become nuclear powers in time of war." 2 The concern is that, at the moment the aircraft loaded with the bomb is on the runway ready to start, the control of the weapon is turned over from the U.S., a nuclear weapon state, to non-nuclear weapon states . The control over this weapon in the physical sense, as well as in the legal sense, is at that moment with the pilot from the non-nuclear weapon state. Control remains with the United States until that point. To my understanding, this is in violation of the spirit if not the text of Articles I and II of the NPT.

During the negotiations for the NPT, NATO’s member states used a rather tricky approach to get around a prohibition of their established system of jointly deciding and implementing specific aspects of NATO’s nuclear strategy. Once the text of Articles I and II was known, the U.S. (in coordination with its allies) worked on a unilateral interpretation of Articles I and II, which they agreed upon internally and then consulted with some of the other countries negotiating the NPT. Who was consulted was not widely known until recently. We now know that the Soviets had been shown the text of these interpretations and that some key members of the Eighteen-Nation Committee negotiating the NPT had been consulted. However, it is still not known which nations were among the "key" members. Most of the States that signed the NPT on July 1, 1968, had not had a chance to see the text of these interpretations at that time.

The normal way to make reservations known to all future and current parties of an international treaty would be to deposit them jointly with the signature of the treaty. Thus they would be in the public domain. However, the U.S. government at the time decided to not deposit any reservation, but make its unilateral interpretations to the NPT public in a different way. They were presented during the Senate ratification hearings in 1968 and later printed in the hearing’s transcript. Thus most initial signatories of the NPT got the chance to learn of the reservations when looking at the U.S. Senate hearing transcripts, which were held after they had already signed the treaty

Because most, if not all, non-NATO countries did not fully understand what NATO nuclear sharing meant in detail, this procedure in effect assured that no early questions about NATO nuclear sharing would be raised by countries not privy to the limited NPT consultations among a few of the parties.

The unilateral U.S interpretations of the NPT were described in an undated letter from then-U.S. Foreign Secretary Rusk, in answers to ‘hypothetical’ questions asked by the European NATO allies. 3 The first three questions dealt with nuclear sharing, the fourth one with the future of the European Union. In this letter, the United States tried to legalize under the NPT what NATO had been doing anyway.

The Rusk letter argues that the NPT does not specify what is allowed, but only what is forbidden. In this view, everything that is not forbidden by the NPT is allowed. Since the treaty doesn’t explicitly forbid the U.S. or other nuclear-weapon states to sell nuclear-weapons-capable carrier systems, such as aircraft, missiles, etc., to non-nuclear weapon states, it is allowed to sell them. Since the treaty doesn’t explicitly talk about the deployment of nuclear warheads in countries that are non-nuclear weapon states, such deployments are considered legal under the NPT. And since the treaty doesn’t talk explicitly about whether it applies or is binding in times of war, a very specific argument has been developed so NATO can argue that this treaty is not binding in times of war.


Limits of NPT applicability?

The question of whether the treaty applies in times of war is a very crucial one to the interpretation of the legality of nuclear sharing.

Adrian Fisher, the U.S. diplomat who developed this U.S. negotiating concept, suggested, referring to the NPT's preamble, that the treaty should have the purpose of prohibiting not only proliferation but also war. Fisher went on to argue that, if such a formula was contained in the preamble, the U.S. could claim that, once a war had begun, the treaty had failed to fulfill its function of prohibiting war and thus was no longer binding on the United States and its allies.4 The suggestion was adopted and is now contained in the treaty text, which declares that the treaty is intended to "to make every effort to avert the danger of such a war," meaning nuclear war. 5

The Rusk letter also reflects this view. It states that the United States and its NATO allies will feel bound to the NPT, "unless and until a decision were made to go to war, at which time the treaty would no longer be controlling."6 The provision allows NATO to argue that both a policy that includes possible first use of nuclear weapons and nuclear sharing is legal in times of war.

The question of what type of war it might take to suspend the NPT arose during the Senate hearings. The Johnson Administration replied that they were talking about "general war."7 However, while general war is defined in U.S. military strategy, the term is not used or defined by NATO. Wars between two minor powers were excluded from the definition of "general war" during the hearing. Rather the term applied to an East-West conflict during which NATO wouldn’t be bound to the treaty.8 Such a view allowed NATO some flexibility to decide itself when the NPT should apply and when not, and when NATO might undertake a first use of nuclear weapons.

Recent developments in NATO make things even more complicated. NATO is currently working on a new classified military strategy document called MC-400/2, in which some want the Alliance to retain the option to assign to nuclear weapons a role in deterring biological and chemical weapons owners as well as those having the means of delivery for such weapons. The document was approved by NATO’s North Atlantic Council in May 2000. To my knowledge, it does not contain a clear approval of deterring all types of weapons of mass destruction by nuclear weapons. However, it also does not contain language clearly restricting the use of nuclear weapons to situations, where nuclear weapon state are involved in the conflict. Since the exact language is unknown to the public it remains an open question, whether like in the case of NATO’s "first use policy," the option for a wider role of nuclear weapons is kept open via the argument "Allowed is what is not explicitly forbidden."

Retaining the option to use nuclear weapons against opponents armed with biological and/or chemical weapons would increase the number of occasions under which NATO might consider nuclear sharing and under which non-nuclear weapon states may participate in nuclear missions. This is a logical consequence of the Alliance’s policy of shared risks, roles and responsibilities.


Nuclear Sharing and the European Union

Nuclear sharing might become a problem for the European Union (EU), too. The EU is likely to face similar questions as has NATO when it no longer discusses joint military crisis-management, but begins to give detailed shape to its collective defense. At some point in the future the EU’s members will have to decide whether to integrate their military forces into a collective defense structure or even whether they are going to become a unified state with unified armed forces. In both cases, the question remains of how current or possible future EU members will address the use of nuclear weapons that belong to the two European Union members that are nuclear powers, Britain and France.

European integration often seems to happen on a slippery slope towards integration. This might prove true again, when it comes to discussing Europe’s nuclear future. A one-time decision to hand over control from the national, i.e. British and French, level to the European level is very unlikely. Interim steps, e.g. some version of nuclear sharing modeled after NATO, could be used to avoid a clear-cut decision on a highly complicated issue such as the future control over British and French nuclear weapons.

At present the fate and the legality of EU nuclear sharing would appear to depend in part on the resolution of the NATO nuclear sharing question. One should try to ensure that the European Union doesn’t run the risk of causing suspicions about the EU violating the NPT in a manner similar to NATO.



1. The issue of the legality of NATO nuclear sharing has never been fully and thoroughly addressed by the parties to the NPT. They need to do so. Unless NATO does not deliberately end nuclear sharing, the parties to the NPT should develop a joint understanding on whether it is legal or not.

2. NATO’s non-nuclear countries should consider whether they would take the unilateral initiative to give up the technical capability to use nuclear weapons. This could be a very, very positive step for strengthening the NPT because it eliminates all ambiguity on whether these countries are in compliance with Article II.9 After all, these countries are parties to the NPT and they have an obligation not to receive nuclear weapons or plan for taking control of them in the future, directly or indirectly. The U.S. should consider whether it not in its vital interest to end nuclear sharing in order to avoid any ambiguity on compliance with Article I of the treaty.

3. Both the non-nuclear as well as the nuclear State Parties to the NPT should consider strengthening and reiterating a formula from the 1985 Third Review Conference final document: that the treaty is controlling under "any circumstances"10 This approach would make it clear that the NPT is binding in times of war. This would end the ambiguity created by the U.S. and its NATO allies in regard to nuclear sharing.

4. Non-nuclear and nuclear members of the EU should assure the other members of the NPT that the EU is not going to develop at any time a nuclear sharing model that might violate or create ambiguity over their compliance with Articles I and II of the NPT. This would make clear its very strong commitment to strengthening the non-proliferation regime.


ist freier Journalist und leitet das Berliner Informationszentrum für Transatlantische Sicherheit (BITS).


1 Otfried Nassauer is the Director of the Berlin Information-center for Transatlantic Security (BITS). This article is based on the transcript of a talk he gave at IEER's Conference on Nuclear Disarmament, the NPT, and the Rule of Law at the United Nations in New York on April 25, 2000. (The original transcript is on-line at His talk was based on research done for a report published in March 2000 by BITS and BASIC entitled "Questions of Command and Control," on-line at
2 Charles E. Johnson, "U.S. Policies on Nuclear Weapons," Washington, December 12, 1964, partially declassified in 1991 (Lyndon B. Johnson Library).
3 "Questions on the Draft Non-Proliferation Treaty Asked by U.S. Allies Together with Answers Given by the United States," in: "Non-Proliferation Treaty" Hearings before the Committee on Foreign Relations," U.S. Senate, Executive H 90th Congress 2nd Session, Washington, 1968, pp. 262-263. This letter was part of the ratification documents, sent by the President to the Senate on July 2, 1968 – one day after the signing ceremony for the treaty. The initial public hearings on these documents were held on July 10, 11,12 and 17, 1968.
4 Adrian Fisher, "Memorandum for Mr Bill Moyers, Subject: Working Group Language for the Non-Proliferation Treaty: Relationship to Existing and Possible Allied Nuclear Arrangements," September 30, 1966, Original Classification Secret-Exdis, pp. 4-5.
5 "Non-Proliferation Treaty"-Hearings before the Committee on Foreign Relations," U.S. Senate, Executive H 90th Congress 2nd Session, Washington, 1968, p. 258.
6 op. cit.
7 "Non-Proliferation Treaty"-Hearings before the Committee on Foreign Relations", U.S. Senate, Executive H 90th Congress 2nd Session, Washington, 1968, p. 60.
8 "Non-Proliferation Treaty"-Hearings before the Committee on Foreign Relations", U.S. Senate, Executive H 90th Congress 2nd Session, Washington, 1969, p. 424.
9 For a longer description of the pro’s and con’s of this proposal see Otfried Nassauer and Markus Nitschke, "Die NATO, Europa und das Ende der technischen nuklearen Teilhabe, BITS-Policy Note 00.7, Berlin, December 2000, available at
10 Final Declaration of the Third Review Conference of the NPT, reprinted in: Jozef Goldblat, "Twenty Years of Non-Proliferation Treaty – Implementation and Prospects," Oslo, 1990, p. 138.