The Geography of Nuclear Restraint in a Fragmenting Order

Five treaty-based nuclear-weapon-free zones (NWFZs), established through the Treaties of Tlatelolco, Rarotonga, Bangkok, Pelindaba and Semipalatinsk, together with Mongolia’s internationally recognised single-state nuclear-weapon-free status, now cover more than one hundred states and most of the Southern Hemisphere. They have evolved beyond their original function as legal instruments prohibiting nuclear weapons in defined territories and now operate as practical mechanisms of regional security governance, nuclear risk reduction, and political restraint.

This report argues that NWFZs play an essential role in maintaining nuclear order and, with the erosion of arms control, are emerging as one of the last enduring treaty-based frameworks for collective nuclear restraint. NWFZs help keep nuclear competition out of regional security practice, reinforce confidence among neighbouring states, support safeguards and peaceful nuclear governance, and in some regions provide frameworks for addressing environmental harm and other nuclear legacies. While negative security assurances remain important, they represent only one part of the zones’ broader security logic.

Drawing on consultations conducted by Open Nuclear Network (ONN) with representatives of all existing zones and members of the UN General Assembly’s Qualified Group of Experts, the report finds that the present regime is both more valuable and more uneven than is often recognised. The zones have shown considerable durability and adaptability, but they also face unresolved protocol questions, institutional and capacity constraints, weak coordination across zones, and structural gaps affecting states that do not fit the classic regional (zonal) model. These findings have implications for future zone development, for the wider NWFZ community, and for the  engagement of nuclear-weapon states (NWS) with zones as practical instruments of regional and global nuclear risk reduction.