Negative Security Assurance Doctrine

A negative security assurance (NSA) is a commitment by a nuclear-armed state that it will not employ or threaten to employ nuclear weapons against states that do not possess them. NSAs are distinct from positive security assurances, which promise assistance to a non-nuclear state if it is attacked or threatened with nuclear weapons.

The doctrine emerged in the context of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), which entered into force in 1970. Non-nuclear-weapon states argued that, having forsworn nuclear arms under the NPT, they were entitled to legally binding guarantees against nuclear attack. In response, the five NPT-recognised nuclear-weapon states issued unilateral declarations. These were noted by the UN Security Council in Resolution 984 (1995), adopted just before the NPT Review and Extension Conference that indefinitely extended the treaty.

NSAs are generally conditional. Most of the P5 reserve the right to use nuclear weapons against a non-nuclear state if that state attacks them in alliance with a nuclear-weapon state, or if it is in material breach of its non-proliferation obligations. China is the notable exception, having maintained an unconditional no-first-use policy and an unconditional NSA since 1964.

Stronger, legally binding NSAs are found in the protocols to nuclear-weapon-free-zone (NWFZ) treaties, such as Tlatelolco (Latin America), Rarotonga (South Pacific), Pelindaba (Africa), Bangkok (Southeast Asia) and Semipalatinsk (Central Asia). Nuclear-weapon states sign these protocols selectively and often with interpretive reservations.

Debate over NSAs intensifies during NPT Review Conferences, where non-aligned states press for a single, legally binding instrument. Critics argue that conditional assurances preserve nuclear coercion; defenders contend that unqualified pledges would erode deterrence against chemical, biological or large-scale conventional attack. The 2010 U.S. Nuclear Posture Review narrowed but did not eliminate the conditions on the American NSA, and subsequent reviews have largely retained that framing.