Only one state not party—the United Kingdom—engaged in conduct in 2022 that was not compatible with the TPNW’s prohibition on receiving the transfer of or control over nuclear weapons. As discussed in the section above, the United Kingdom leases Trident missiles and imports other key nuclear components from the United States.
As discussed in the previous section, the transfers by the United States are not only prohibited by the TPNW, but are also highly questionable under the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). The receipt of the transfers by the United Kingdom as a nuclear-weapon state, however, is not regulated by the NPT. This lacuna is addressed by Article 1(1)(c) of the TPNW, which does not permit any state to receive transfer or control of nuclear weapons.
As also discussed above, the planned replacement for the United Kingdom’s Holbrooke warhead will be partly based on the W93 warhead, which is being developed by the United States. If the United Kingdom receives from the United States comprehensive technical information, such as in the form of a design blueprint, and uses it for the development of its new warhead, this will amount to indirect receipt of transfer under the TPNW.
Another potential future compatibility issue under this prohibition concerns the US B61 nuclear bombs stored in Europe. Arrangements are reportedly in place for control over the bombs to be given by the United States to the host states Belgium, Germany, Italy, and the Netherlands, for loading and use on their dual-capable NATO-designated aircraft. If this were to occur such that the receiving state could use the weapons itself, this would contravene Article 1(1)(c) of the TPNW (and also the NPT). This specific task division arrangement has therefore been much discussed, not least when the German Bundeswehr in 2008 handed out directives, in the form of a pocket card (‘Taschenkarte’), stipulating that German soldiers were prohibited from using nuclear weapons under international law.The directives have since been changed and the sentence in question omitted.
Currently, Belgium, Germany, Italy, and the Netherlands all have an active nuclear role in NATO and retain the dual-capable aircraft and pilots trained in the use of the weapons at bases on their territory. The weapons are controlled by the United States but could be released to the host country for use in a war. In the case of the B61 bombs stationed at Incirlik in Türkiye, however, any use of the weapons would reportedly be carried out by NATO aircraft stationed at other bases. Türkiye’s F-16 fighters are capable of delivering nuclear bombs but are not fully certified to do so. A seventh state, Greece, also contributes to the nuclear sharing mission. Greece does not have a committed fighter unit, but has a contingency mission.
Belgium, Germany, Italy, and the Netherlands are procuring the F-35A fighter aircraft to continue the nuclear-sharing arrangements. In the Netherlands, a majority of the members of parliament supported a motion in 2014 stating that the F-35s should have no nuclear role. The Dutch government decided to ignore the parliamentary vote, opting to procure nuclear-capable F-35s. Germany decided in March 2022 to replace its ageing Tornado fleet, which includes nuclear-capable aircraft, with F-35 fighters. The decision, which was taken following Russia’s invasion of Ukraine, was formally ratified by the German Parliament in December 2022. The ‘Block 4’ software upgrade enabling the F-35A to employ nuclear weapons is expected to be implemented across the relevant host states through 2026.
See the section on the prohibition on allowing stationing, installation, or deployment of nuclear weapons for further information on the US nuclear weapons stored in Europe.