Fifty years after five Southeast Asian leaders gathered in Bali to sign the Treaty of Amity and Cooperation in Southeast Asia, the agreement has expanded far beyond the region that created it.
On July 24, 2026, Lithuania, Poland, Romania, and Sweden formally joined the treaty during the 59th ASEAN Foreign Ministers’ Meeting and Related Meetings in Manila. Their accession raised the number of High Contracting Parties to 62, turning the TAC’s golden jubilee into both a celebration of ASEAN diplomacy and a reminder that its founding principles continue to resonate in a divided world.
Born in Bali, Built for a Divided Region
The TAC was signed on February 24, 1976, during the first ASEAN Summit in Bali, Indonesia. At the time, Southeast Asia was emerging from decades shaped by colonialism, confrontation, the Vietnam War, and intense Cold War rivalry.
Indonesia, Malaysia, the Philippines, Singapore, and Thailand sought to create a more predictable regional environment. The treaty established a code of conduct based on respect for sovereignty and territorial integrity, freedom from external interference, non-interference in domestic affairs, peaceful dispute settlement, renunciation of force, and effective cooperation.
These principles became closely associated with what is now called the “ASEAN Way”—an approach centered on consultation, consensus, patience, and quiet diplomacy rather than confrontation.
The treaty did not eliminate every dispute or political tension. Yet ASEAN’s original members avoided major interstate war, expanded their economic cooperation, and eventually welcomed Brunei Darussalam, Vietnam, Laos, Myanmar, Cambodia, and Timor-Leste into a regional organization that now comprises 11 countries.
As Philippine Foreign Affairs Secretary Ma. Theresa Lazaro observed during the anniversary conference, “Peace transformed Southeast Asia from a region of turmoil into a global economic powerhouse.”
A Southeast Asian Treaty Goes Global
The TAC was originally designed to govern relations among Southeast Asian states. Its transformation into a global diplomatic instrument began when ASEAN opened accession to countries outside the region.
Major powers and regional partners gradually joined, including China, India, Japan, South Korea, Russia, the United States, and the European Union. By early 2026, the treaty had 58 High Contracting Parties. The four European accessions in Manila brought the total to 62.
The latest signatories are especially significant because all four are European Union members navigating a security environment shaped by war, strategic competition, and pressure on the rules-based international order.
Their decision to join a treaty created in Southeast Asia represents recognition that ASEAN is not merely a collection of smaller states operating between major powers. It is also a producer of diplomatic norms.
By signing the TAC, Lithuania, Poland, Romania, and Sweden formally endorsed ASEAN’s principles of peaceful coexistence, sovereign equality, dialogue, and cooperation. Their accession increased the number of European signatories to 13, in addition to the European Union itself, which became a contracting party in 2012.
The development also reinforces ASEAN’s role as a platform where competing powers can remain engaged even when they disagree elsewhere. Foreign ministers and senior representatives from countries with sharply different strategic interests continue to meet through ASEAN-led mechanisms such as the ASEAN Regional Forum, East Asia Summit, and Post-Ministerial Conferences.
The Appeal of a Diplomatic Middle Ground
The TAC’s continued expansion reflects the value of ASEAN’s neutral diplomatic space.
For middle powers, signing the treaty offers a way to deepen political relations with Southeast Asia without entering a military alliance or choosing sides in major-power competition. It signals respect for ASEAN centrality and establishes a foundation for broader cooperation in trade, education, technology, maritime security, climate action, and people-to-people exchange.
For ASEAN, every accession strengthens its claim to remain at the center of the wider Indo-Pacific diplomatic architecture.
The treaty has therefore become more than a historical document. It functions as an entry point into ASEAN’s political community and an expression of how external partners intend to conduct their relations with the region.
During the Manila anniversary events, Thai Foreign Minister Sihasak Phuangketkeow described the TAC as a cornerstone of peaceful interstate relations and encouraged its parties to use it as a platform for practical cooperation against transnational crime, climate change, and the erosion of multilateralism.
Myanmar Tests the Limits of Non-Interference
The golden jubilee also arrives at a difficult moment for ASEAN.
Myanmar’s continuing political and humanitarian crisis has exposed the limitations of a regional system built around non-interference and consensus. ASEAN adopted its Five-Point Consensus in 2021, calling for an end to violence, constructive dialogue, humanitarian assistance, a special envoy, and engagement with all parties.
Implementation has remained limited.
At the July 2026 ministerial meetings, ASEAN again called for concrete and measurable progress, including a permanent cessation of violence, the release of political prisoners, and safe humanitarian access. The bloc maintained the Five-Point Consensus as its primary framework while acknowledging that Myanmar’s full return to high-level ASEAN meetings remained distant.
The crisis has created a deeper institutional debate. The TAC’s non-interference principle was designed to prevent coercion and protect newly independent states. Yet critics argue that strict adherence can restrict collective action when domestic violence produces regional humanitarian, security, and migration consequences.
ASEAN faces the challenge of responding more effectively without abandoning the sovereign equality that holds its diverse membership together.
The South China Sea Challenges Peaceful Settlement
Maritime tensions provide another test of the treaty’s credibility.
The TAC requires parties to renounce the threat or use of force and settle disputes peacefully. These commitments are directly relevant to the South China Sea, where overlapping territorial and maritime claims continue to produce confrontations involving coast guard vessels, fishing fleets, and other state-linked actors.
ASEAN and China have spent years negotiating a Code of Conduct intended to manage behavior and reduce the risk of escalation. In July 2026, ASEAN officials reported progress and expressed hope that negotiations could be completed within the year, although several complex issues remained unresolved.
The difficulty lies not in agreeing that peace is desirable, but in translating general principles into enforceable behavior at sea.
A credible code would need to complement the TAC, the United Nations Convention on the Law of the Sea, and existing regional commitments. Without practical mechanisms for restraint, communication, and accountability, the gap between diplomatic language and maritime realities will remain wide.
From Non-Interference to Responsible Cooperation
The TAC does not necessarily require rewriting to remain relevant. Its principles are broad enough to guide responses to contemporary challenges, but their implementation may need to evolve.
Non-interference should not become indifference. Consensus should not become paralysis. Quiet diplomacy should not prevent ASEAN from speaking clearly when regional peace and human security are threatened.
The next phase of the treaty could place greater emphasis on preventive diplomacy, humanitarian access, crisis mediation, maritime confidence-building, and cooperation against transnational threats.
The first High-Level Conference of the TAC’s High Contracting Parties, convened during the 50th anniversary events in Manila, represented an important step in that direction. Its discussions covered conflict prevention, maritime cooperation, and emerging security challenges, showing how the treaty could develop from a statement of principles into a more active diplomatic platform.
The Next Fifty Years
The Treaty of Amity and Cooperation has survived because it reflects the political realities of Southeast Asia: diverse states, unequal power, difficult histories, and a shared interest in preventing conflict.
Its global expansion demonstrates that the ASEAN Way still carries diplomatic appeal. Countries far beyond Southeast Asia are willing to associate themselves with a framework centered on sovereignty, restraint, and dialogue.
Yet the treaty’s future will depend less on the number of signatures it collects than on the behavior those signatures inspire.
At 50, the TAC is neither obsolete nor complete. It remains ASEAN’s diplomatic shield, but it must also become a more practical instrument for addressing crises that cross borders, threaten civilians, and test regional unity.
The journey that began in Bali now belongs to 62 parties. The task for the next half-century is to ensure that their commitment to amity and cooperation is visible not only in ceremonial documents, but also in the choices they make when peace is under pressure.
