The Stepping Stones Approach, the TPNW, and the Value of Complementarity for Sustainable, Verifiable Disarmament

This article has been co-authored by Emily Enright and Eva-Nour Repussard.


Disarmament proponents often cite South Africa as a disarmament success story, it having renounced nuclear weapons and dismantling its nuclear programme almost overnight. The example set by South Africa reinforces the notion that disarmament can happen suddenly, given sufficient political will and with a strong impetus for change boosted by favourable strategic conditions. Nonetheless, the South African case of “nuclear roll-back” is unique, and may be irreplicable. Different methods to achieve disarmament, such as the Stepping Stones Approach which emphasises a sustainable, incremental and stepwise approach rather than mandating sudden renunciation, ought to be embraced as, in all likelihood, successful disarmament by the remaining nuclear-armed states will require collaboration, innovation, and multimodality. 

The ‘Stepping Stones Approach’ to nuclear disarmament (the SSA) and the Treaty on the Prohibition of Nuclear Weapons (the TPNW) speak to two very different, and quite complementary, disarmament methodologies. The TPNW is a classical legal instrument, borrowing its logic from historic abolitionist efforts pertaining to landmines and cluster munitions. As the first legally-binding treaty on nuclear disarmament and prohibition, it fills, its proponents claim, a ‘legal gap’ in the NPT that purportedly allows the five NPT ‘Nuclear-Weapons States’ (NWS) to maintain their arsenals indefinitely. The SSA, on the other hand, is the product of deliberations within the Stockholm Initiative, a grouping of sixteen states committed to pursuing progress on the NPT’s disarmament pillar. The 2019 SSA joint working paper outlines a set of pragmatic, incremental steps towards disarmament that emphasise tangible outputs, meaningful dialogue and collaboration on common security challenges. It is centred on existing commitments made by NPT states parties on issues such as negative security assurances, nuclear-weapons-free zones, and reducing the role of nuclear weapons in NWS’ security policies and doctrines. 

The SSA consists of twenty-two implementable, concrete actions (stepping stones) that are reflective of states’ national security concerns and lived strategic reality. One important characteristic of the SSA is that many of the stepping stones can be implemented without requiring changes to NWS’ nuclear postures, and do not necessitate perceived strategic sacrifices. In this way, while the SSA furthers the Stockholm Initiative’s aims of reducing the salience of nuclear weapons, rebuilding habits of cooperation, reducing nuclear risks and enhancing transparency, it sets modest initial goals that build capacity and set the scene for further steps.

The TPNW and the SSA share a common goal, as stated explicitly in the preamble of both the SSA Joint Working Paper and TPNW text: achieving and maintaining a world free of nuclear weapons. Beyond this essential objective, the SSA and TPNW unite on their central points. Both affirm the need to ensure that nuclear weapons are never used again, recognise the centrality of the Nuclear Non-Proliferation Treaty (NPT) as the cornerstone of the nuclear disarmament regime, and call on nuclear-armed states to reduce the role of these weapons in their security policies and doctrines as a facilitating step towards disarmament. 

Vitally, the SSA and TPNW are neither competing nor internecine, but mutually reinforcing in advancing disarmament. They offer states distinct workstreams and complementary logics, enabling them to make progress on disarmament commitments from a variety of angles and using a range of logics, instead of requiring states to prioritise one over the other. For example, encouraging the creation and expansion of zones free of nuclear weapons, supporting the moratorium on nuclear weapons testing and recognising the Comprehensive Nuclear Test Ban Treaty (CTBT), and expanding engagement with and support for communities affected by nuclear weapons activities are common imperatives within the TPNW and SSA. Progress in these areas would represent both normative progress within the SSA, and a contribution to the fulfilment of legal obligations under the TPNW. 

The SSA and TPNW target and instrumentalise policymaking in discrete yet intersecting ways, together contributing to and enhancing the normative and legal architecture underpinning practical disarmament work. Applying the SSA does not preclude Nuclear Weapons States (NWS) from later signing the TPNW, and nor does it require them to; as an approach, rather than an instrument, states are able to engage with the SSA fluidly and organically. The SSA, thus, should be seen as a separate tool in states’ ‘disarmament toolbox’ rather than a competitor to more formal disarmament institutions, and is available for states to harness in a way that suits their disarmament priorities and security needs. Alongside other methods and instruments for disarmament, the SSA and TPW form a ‘two-pronged’ strategy; the relationship between these tools highlights, if nothing else, the power and utility of multimodality in our work to build a safe, sustainable world free of nuclear weapons. Success will hinge on the application of a ‘patchwork’ of complementing tools and methods, rather than the pursuit of only one. The SSA offers a useful framework for progress that operationalises past commitments, and which will tessellate neatly with the TPNW amongst other institutions and instruments.

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