In addition to the nine nuclear-armed states, 31 other states also base their security strategies on the retention and potential use of nuclear weapons, perpetuating nuclear risks and undermining the international community’s longstanding goal of nuclear disarmament. They do not possess nuclear weapons but have outsourced their nuclear postures to one or more nuclear-armed allies. The Ban Monitor refers to them as “nuclear-weapon-complicit states”.
The role of the 31 nuclear-weapon-complicit states in assisting, encouraging, and /or inducing continued retention of nuclear weapons had not been given much attention prior to the humanitarian initiative and the process that led to the negotiation and adoption of the TPNW. They have incorporated extended nuclear deterrence (sometimes called a nuclear “umbrella”) in their military doctrines. They have officially endorsed or acquiesced in the retention and potential use of nuclear weapons on their behalf. Even with the obvious credibility problem inherent in the policy of extended nuclear deterrence (a nuclear-armed state is exceedingly unlikely to risk nuclear war for anything other than serious or even existential threats to its own national security) these 31 states function as enablers of nuclear armament and share responsibility for the perpetuation of nuclear risks.
All of the nuclear-armed members of the North Atlantic Treaty Organization (NATO) – France, the United Kingdom, and the United States – frequently use their allies’ avowed demand for nuclear protection as an argument for their own nuclear possession and modernisation.
Note, however, that not all military alliances that include a nuclear-armed state are automatically an extended- nuclear-deterrence arrangement or nuclear “umbrella”. For example, Kazakhstan, Kyrgyzstan, the Philippines, Tajikistan, and Thailand all maintain military alliances with either Russia or the United States but have through national statements, or signature and ratification of international agreements signalled that they do not support the use of nuclear weapons under any circumstances.
The 29 (soon to be 30 when North Macedonia’s accession enters into force) members of NATO have accepted potential nuclear weapon use through their endorsement of various alliance documents. According to NATO’s 2012 “Deterrence and Defence Posture Review”, the “supreme guarantee” of the allies’ security “is provided by the strategic nuclear forces of the alliance”. While some of the alliance’s members maintain policies not to allow the stationing of nuclear weapons on their territories, none of them has so far rejected the use, or even the first use, of nuclear weapons on its behalf.
US allies Australia, Japan, and South Korea have also made explicit statements or published strategy documents endorsing the potential use of nuclear weapons on their behalf. The governments of the United States and Japan expressed through a joint statement in 2013 that they remained committed to the security of Japan “through the full range of US military capabilities, including nuclear and conventional.” South Korea has endorsed similar statements. With respect to Australia, a 2016 Australian White Paper on defence appears to directly encourage the United States to retain nuclear weapons: “Only the nuclear and conventional military capabilities of the United States can offer effective deterrence against the possibility of nuclear threats against Australia.”
The Russian-led Collective Security Treaty Organization (CSTO) has also been understood by certain observers as a nuclear alliance. In 2010, the CSTO’s Secretary-General suggested Russia had extended a “nuclear umbrella” over all members of the alliance. Yet, the CSTO’s members do not appear to have adopted official documents stipulating a nuclear dimension to the alliance. On the contrary, three of the CSTO’s members have actively distanced them- selves from nuclear deterrence. Through the 2006 Treaty of Semipalatinsk – the treaty establishing Central Asia as a nuclear-weapon-free zone (NWFZ) – Kazakhstan, Kyrgyzstan, and Tajikistan have committed never to “assist or encourage” the development, manufacture, or possession of nuclear weapons. Kazakhstan has also signed and ratified the TPNW.
Belarus, however, which is allied to Russia through the CSTO and the Union State, has previously expressed public support for nuclear deterrence. Armenia, the last CSTO member, has, to our knowledge, not explicitly endorsed the potential use of nuclear weapons on its behalf, but has also not publicly rejected this (or the statement of the CSTO Secretary-General). The Ban Monitor therefore includes Armenia among the nuclear-weapon-complicit states.
An overview of the members of arrangements of extended nuclear deterrence is included below
Arrangements of extended nuclear deterrence
 NATO, “Deterrence and Defence Posture Review” (20 May 2012), para.II(9).
 See e.g. International Law and Policy Institute, “Under my Umbrella”, Report, 2016, p. 8, at: bit.ly/2mWvRHp.