The first draft of the nuclear weapons ban treaty (I suppose we should start calling it ‘the prohibition convention’ now) does not ban the ‘threat of use’ of nuclear weapons. This omission has led some commentators to suggest that the ban treaty would allow the practice of nuclear deterrence. I propose a radically different reading of the draft: while the existing draft’s combination of prohibitions against ‘possession’ and ‘assistance, encouragement, and inducement’ of prohibited acts does in fact effectively outlaw the practice of nuclear deterrence, a ban against the ‘threat of use’ of nuclear weapons would not.
It is certainly true that the doctrine of nuclear deterrence relies, at a minimum, on an implicit threat of use – a ‘possibility of use’ – but the mere possession of a weapon cannot, it seems to me, reasonably be described as a ‘threat’. Such an understanding of the word ‘threat’ would certainly not square well with international custom. After all, the threat of use of force is already generally prohibited under international law. Yet almost all the world’s states maintain conventional armed forces. And like nuclear weapons, these forces exert – and are intended to exert – a deterrent effect on potential aggressors. Yet few would argue that Finland or Cameroon or Paraguay are in constant violation of the UN Charter’s prohibition against the threat of use of force because they rely on a strategy of (conventional) deterrence. Such an argument could only be sustained by a claim that these states are continuously exercising their right to self-defence as codified by Article 51 of the UN Charter. But given that Article 51 limits the right of self-defence to situations where ‘an armed attack occurs against a Member of the United Nations’, such a view appears difficult to maintain.
I readily admit that certain (many? most?) nuclear deterrence practices can be understood as threats – Russia’s recent ‘warnings’ to countries like Norway and Denmark certainly look like threats from Oslo and Copenhagen – but the overlap between the concepts of ‘threat’ and ‘deterrence’ is not perfect. First and rather obviously, one may threaten but fail to deter (see: the immediate run-up to almost all wars ever). Second and more importantly, it is possible to practice deterrence without issuing a ‘threat’ as that word is commonly understood. Israel, for example, practices nuclear deterrence without even having officially admitted to possessing nuclear weapons.
If I am correct that the practice of nuclear deterrence only requires the faintest ‘possibility’ of use – not an active ‘threat’ – a ban against ‘threat of use’ of nuclear weapons clearly would not ban nuclear deterrence in all its forms. Rather, what one would have to target to eliminate any scope for lawful deterrence would be the ‘possibility’ of use. And a ‘possibility of use’, I would argue, can only be prohibited by banning ‘possession’. Add to that a ban on ‘assistance, encouragement, and inducement’ of prohibited acts, and you have effectively prohibited both ‘individual’ and ‘extended’ nuclear deterrence. After all, you cannot lawfully threaten to use a weapon you are not allowed to possess. And you cannot subscribe to the policy of extended nuclear deterrence if you are not allowed to encourage your friends to possess (or use, or acquire, or transfer, or station etc.) nuclear weapons. This point could be made even clearer through the inclusion in the prohibition convention of an article obligating parties to actively promote the convention’s letter and spirit. The draft convention’s preamble could also be buttressed with a sentence or two making clear that signing on to the agreement constitutes a disavowal of the possession and use of nuclear weapons by any actor, under any circumstances.
For states that do not possess nuclear weapons but are engaged in military alliances that include one or more states that do possess such weapons, signing a convention like or similar to the present draft would constitute a withdrawal from the alliance’s ‘nuclear umbrella’, but not from its broader ‘security umbrella’. A state like Australia, for example, could sign the ban treaty and continue its security cooperation with the United States on the understanding that the latter would never use or retain nuclear weapons in Australia’s name.