One Nuclear-Free Principle, Two Strategic Realities
The visits of the nuclear-powered USS Abraham Lincoln and USS George Bush to Thailand in September and October 2026 illustrate a longstanding feature of Southeast Asia’s security architecture. Despite ASEAN’s commitment to maintaining a nuclear-weapon-free region, its member states continue to accommodate the military presence of nuclear-armed powers. Across the Indo-Pacific, New Zealand has pursued a more restrictive nuclear-free policy, prohibiting nuclear-powered vessels from entering its internal waters. The contrast raises an important question: why have two proponents of nuclear-free principles adopted such different approaches to foreign military access and is this sustainable?
For Thailand, visits by US aircraft carriers are an established feature of its defence relationship with Washington. Rooted in 1954 Manila Pact and the 1962 Thanat-Rusk communique, this relationship has remained central to Thai security policy. Thailand’s designation as a Major Non-NATO Ally in 2003 further reinforced bilateral defence cooperation. Elsewhere in Southeast Asia, US nuclear-powered aircraft carriers have made port visits to the Philippines, Malaysia, Singapore and Vietnam. These visits highlight the continued importance of US naval engagement in the region amid intensifying Great-power rivalry.
Yet these visits do not necessarily contradict ASEAN’s nuclear-weapon-free commitments. Rather they reveal fundamental differences in legal architecture, geostrategic circumstances, and political foundations underpinning nuclear-free policies in Southeast Asia and New Zealand.
The first distinction lies in their respective legal frameworks. Established under the 1995 Bangkok Treaty, the Southeast Asia Nuclear Weapon-Free Zone (SEANWFZ) prohibits member states from developing, manufacturing, acquiring, possessing, stationing or transporting nuclear weapons. However, Article 7 preserves each member states’ discretion over visits by foreign ships and aircraft to its ports and airfields that may be nuclear capable or powered. Crucially, the treaty does not prohibit nuclear propulsion itself. The presence of nuclear-powered warships therefore does not automatically constitute a breach of ASEAN’s nuclear-weapon-free obligations. Furthermore, the treaty aspires to build on the ASEAN’s earlier adoption in 1971 of the Zone of Peace and Neutrality (ZOPFAN).
New Zealand’s Nuclear Free Zone, Disarmament, and Arms Control Act 1987 goes further. Beyond restrictions concerning ‘explosive nuclear devices’ Article 11 expressly prohibits nuclear-powered ships from entering New Zealand’s internal waters. Unlike ASEAN’s regional treaty, New Zealand’s restrictions are embedded in domestic legislation, enabling successive governments to maintain a relatively uniform policy on foreign naval access. Though the treaty does not block use of the technology as an energy source on land.
This difference reflects more than legal drafting since ASEAN’s treaty emerged from negotiations among sovereign states with distinct security priorities and relationships with external powers – safeguarding their individual strategic sovereignty. Its provisions preserve national discretion over foreign military access, consistent with ASEAN’s longstanding emphasis on sovereignty and non-interference in domestic affairs. New Zealand by contrast, institutionalised its nuclear-free commitments through national legislation following sustained domestic political mobilisation. For New Zealand, anti-nuclear sentiment became the norm and the norm itself led to institutionalisation.
The second distinction concerns varying threat perceptions and geostrategic interests. Southeast Asia occupies a strategically contested region where the security interests of US, China and other major powers intersect. ASEAN members consequently pursue different and varying approaches to managing external relationships. This ranges from formal alliances to non-alignment and diversified defence partnerships. Some ASEAN members (small to middle power states) also engage in hedging as a form of insurance-seeking strategy to not only maintain defence partnerships and economic gains but also navigate great-power rivalry.
Thailand illustrates these complexities. Although it maintains a longstanding security alliance with Washington, Bangkok has simultaneously expanded its diplomatic, economic and defence relations with Beijing. This reflects a broader tendency among some Southeast Asian states to preserve strategic flexibility rather than depend exclusively on one major power. Restricting American naval access could therefore impose costs on Thailand’s defence relationship without necessarily improving its security position.
Therefore, ASEAN members cannot be treated as strategically homogeneous. The Philippines’ alliance commitments, Singapore’s extensive defence cooperation with Washington, and the more independent foreign policies pursued by Malaysia, Vietnam and Indonesia reflect different assessments of regional security and varying threat perceptions. These variations help explain why a collective prohibition on nuclear-powered naval visits would be politically difficult to establish, even where governments share commitments to nuclear non-proliferation.
New Zealand’s nuclear-free policy emerged from a different political and geostrategic environment. Public opposition to nuclear testing in the South Pacific gathered momentum during the Cold War, reinforced by concerns over environmental and humanitarian consequences of nuclear weapons testing. The 1985 bombing of Greenpeace’s Rainbow Warrior by French intelligence agents further intensified anti-nuclear sentiment and reinforced perceptions that nuclear-related threats could also originate from Western partners. Then NZ Prime Minister David Lange in 1985 echoed such sentiment when he said “the only thing worse than being incinerated by your enemies, is being incinerated by your friends”.
The dispute over the proposed visit of USS Buchanan in 1985 marked a turning point. Washington’s policy of neither confirming nor denying (NCND) the presence of nuclear weapons prevented New Zealand from ascertaining whether the vessel complied with its proposed restrictions. Wellington refused the visit, prompting Washington to suspend its ANZUS treaty obligations towards New Zealand. The subsequent 1987 legislation consolidated the country’s nuclear-free position despite the diplomatic and security costs.
Over time, the policy became closely associated with New Zealand’s national identity and political independence. Its endurance reflected not merely geographical distance from major Cold War confrontation zones, but also the institutionalisation of public opposition to nuclear weapons and the political difficulty of reversing an established national and bipartisan commitment.
Nevertheless, New Zealand’s strategic environment is changing. Intensifying US-China rivalry and increasing economic interdependence and Australia’s acquisition of nuclear-powered submarines under AUKUS have renewed questions about the implications of its nuclear-free policy for regional defence cooperation. Future Australian nuclear-powered submarines would remain subject to New Zealand’s existing restrictions on entry into internal waters complicating trans-Tasman defence ties. Additionally, economic interdependence with China, where it accounts for 28% of New Zealand’s overall export and largest trading partner draws limits its strategic manoeuvrability and reduces its geographic isolation.
Foreign Minister Winston Peters’ recent acknowledgement that New Zealand’s nuclear-free policy incurred costs illustrates the enduring tension between strategic commitments and political principles. Yet recognising those costs does not necessarily imply that Wellington intends to abandon its restrictions. New Zealand continues to cooperate militarily with Western partners while maintaining its nuclear-free legislation. So far it has been able to demonstrate that restrictions on nuclear-powered vessels does not preclude it from broader defence engagement in other spheres (e.g. Five Eyes).
The comparison therefore reveals two different approaches (realities) to reconciling nuclear-free commitments with national security interests. New Zealand has institutionalised a restrictive policy through domestic legislation and political consensus, while accepting constraints (costs) on certain forms of defence cooperation. ASEAN, meanwhile, has established a collective prohibition on nuclear weapons while preserving individual members’ discretion over foreign naval access.
Neither approach should be understood simply as evidence of stronger or weaker commitment to nuclear disarmament. Their differences reflect distinct regional norms, legal obligations, political institutions and geostrategic circumstances. As geopolitical competition intensifies across the Indo-Pacific, New Zealand’s geographic isolation may offer diminishing protection from the strategic pressures of great-power rivalry. the challenge for both New Zealand and ASEAN is not merely to reaffirm nuclear-free principles, but to determine how those commitments can be sustained alongside changing security relationships and landscape. Furthermore, the advent of possible conflict in the South China Sea between great powers could continually put New Zealand’s nuclear-free policy under spotlight for assessment and evaluation by its defence partners.
DISCLAIMER: All views expressed are those of the writer and do not necessarily represent that of IIPA and this platform.
Authors
Ratchanon Samosungnoen is a PhD candidate at the University of Canterbury, New Zealand. His current research examines U.S.–China strategic competition in the semiconductor industry, with particular attention to the geopolitical implications of technological rivalry and its effects on middle powers, especially Thailand.
Hazwan Dani Abdul Kadiris a PhD candidate at the University of Canterbury, New Zealand. His current research focuses on foreign policy decision making, conflict escalation and de-escalation, small state security, and state behaviour and response in to asymmetric and conventional conflict environments.