As ASEAN and China work toward concluding a Code of Conduct (COC) for the South China Sea in 2026, the central question is not simply whether an agreement can be reached, but whether it will meaningfully reduce tensions. A deal is not enough if it does not address the underlying drivers of tension and shape actors’ behaviors. 

The South China Sea is a contested maritime zone, involving China and ASEAN members Brunei, Malaysia, the Philippines, and Vietnam. To address the overlapping maritime claims and disputes, ASEAN and China have been negotiating a COC to establish a rules-based framework to manage maritime disputes, reduce miscalculations, and prevent armed conflict. 

After nearly two decades of negotiations, Manila, as the current ASEAN chair, has recently signaled that agreement on the COC is at hand. A COC would represent an important diplomatic achievement. 

Yet an agreement that lacks credible enforcement mechanisms, preserves ambiguity over compliance, or constrains Southeast Asian countries’ strategic autonomy could do little to address the region’s underlying security challenges.

The substance of the agreement matters more than announcing its completion. A COC that primarily reiterates commitments to dialogue, restraint, and peaceful dispute resolution – like those contained in the existing Declaration of Conduct – would have limited practical value. The COC needs clear procedures for managing incidents, resolving disagreements, and addressing violations. 

The South China Sea has seen increased military activities. China has built a network of military facilities in the Spratly and Paracel Islands, some of which are now equipped to host bombers. In 2025, Vietnam commenced its own reclamation work on occupied features, building infrastructure to support a larger military presence. 

Naval confrontations between China and the Philippines continue, highlighting the fragility of stability in the contested waters. Diplomatic commitments alone cannot guarantee responsible behavior

If the COC is to improve regional stability, it must include practical measures to prevent escalation and hold parties accountable for their conduct.

This raises a second challenge: ASEAN’s ability to ensure compliance. Even if the agreement includes specific obligations, its effectiveness will depend on whether parties are willing to implement them when doing so conflicts with their strategic interests. ASEAN’s consensus-based approach, while essential to maintaining regional unity, can complicate collective responses to violations, particularly when member states have different economic and security relationships with China.

A credible COC should therefore establish transparent procedures for reporting incidents, conducting consultations, and addressing alleged breaches. Regular reviews and clearly defined dispute-management channels could help prevent disagreements from escalating. Without a meaningful accountability mechanism, the COC risks just becoming a declaration of intent.

The agreement must also protect Southeast Asian states’ strategic autonomy. China may seek arrangements that limit activities it considers destabilizing, such as joint military exercises with the United States. Provisions governing military exercises, defense partnerships, or cooperation with external powers could create constraints that extend beyond managing disputes in the South China Sea. If drafted too broadly, the COC could inadvertently restrict ASEAN members’ ability to pursue their own security interests.

The challenge is to distinguish between measures designed to prevent maritime incidents and provisions that limit legitimate defense cooperation. Southeast Asian states should retain the freedom to conduct exercises, modernize their armed forces, and establish partnerships with countries outside the region, consistent with international law. A COC that undermines these freedoms would risk weakening the very strategic independence ASEAN seeks to preserve.

The Philippines’ expanding defense cooperation with non-Southeast Asian powers such as Australia and Japan illustrates this tension. Manila’s partnerships strengthen its deterrence capabilities and provide additional options for responding to maritime pressure. However, Beijing may view these arrangements as contributing to strategic competition, complicating efforts to reach a mutually acceptable agreement.

Nevertheless, external partnerships should not automatically be regarded as obstacles to a COC. They can strengthen Southeast Asian states’ negotiating position by showing that China and ASEAN alone cannot determine regional security, given the South China Sea’s significance as an international maritime trade route. Extra-regional powers’ participation in maritime security, however, should not obscure ASEAN’s central role in shaping regional norms.

Ultimately, the COC’s credibility will depend on whether it can reconcile three objectives: reducing tensions, ensuring compliance, and preserving the strategic autonomy of Southeast Asian countries. These objectives are not mutually exclusive, but achieving them will require precise language, practical implementation mechanisms, and a willingness to address violations consistently.

The measure of success, then, is not whether ASEAN and China can sign an agreement, but whether that agreement changes behavior at sea. Without credible commitments and meaningful accountability, the COC may secure a diplomatic milestone while failing to deliver the regional stability it promises.