A treaty negotiated at the UN is an international agreement concluded between states in written form and governed by international law. UN treaties can make useful and significant progress even when not ratified by all the UN states. A good example is the International Criminal Court from which the US has remained aloof, but which has still been able to function and indeed to indict 32 suspected war criminals since its inception in 2002. The bans on landmines and chemical weapons are currently being breached in Syria but their use carries with it both current pariah status and the threat of ultimate prosecution.
The nuclear weapon treaty aims to ban the development, production, testing, acquisition, stockpiling, transfer, deployment and use and threat of use of nuclear weapons, as steps towards their complete elimination. States bound by the treaty would not allow materials, such as uranium, to be produced within their jurisdiction, and would not allow another state to transport nuclear weapons or nuclear weapon-related material within their borders, through their seas or through their airspace. States party to the treaty would also prohibit another state from deploying nuclear weapons from their territory, as happens presently with a number of countries in relation to US weapons. As regards NATO, a ban treaty will make it easier for member states which are not nuclear-armed to work for a nuclear-free alliance.
As well as imposing these practcial difficulties on nuclear-armed states a ban will change the moral atmosphere around nuclear weapons as place them firmly in the category of illegitimate weapons of mass destructions.
In the days before the critical vote at the UN for Conference for a Ban Treaty, the US was writing to its NATO allies in an unclassified briefing spelling out exactly how the treaty could limit and impact on their nuclear military doctrines and capability.
An abolition treaty could make it impossible to undertake ‘nuclear-related transit through territorial airspace or seas’ of the signatories to the abolition treaty, and could force US allies to ‘repudiate US statements that it would defend the signatory with nuclear means’.
It could force dual-capable US naval vessels and aircraft to avoid ports and airports in signatory countries (because the US refuses to confirm or deny the presence of nuclear weapons on its ships or air planes).
If NATO members became signatories to the abolition treaty, this could badly affect NATO exercises and planning, according to the US briefing (available on the ICAN website).
Overall, the US wrote to its NATO allies: ‘The effects of a nuclear weapons ban treaty could be wide-ranging and degrade enduring security relationships’, and the impact had the ‘potential to grow more severe over time’. Read full letter here.
So despite statements that they will not participate because the process will be ineffective, the nuclear weapons states do know that a ban treaty will have an effect on how they function.