Manila's recent move in the South China Sea—designating a military exercise zone that includes China's Huangyan Dao and its territorial waters and airspace—blatantly infringes upon China's territorial sovereignty and maritime rights and interests, and is, by international law, completely illegal. Spanning from Jan 21 to Mar 31, 2026, this expansive military exercise zone represents a serious escalation in regional tensions. This move is not an isolated incident, but rather part of a broader pattern of Philippine assertiveness that prioritizes unilateral gains over collective regional stability.

Under international law, a country cannot extend its military exercise zone into another state's airspace without consent, as airspace is recognized as an extension of national territory. The 1944 Chicago Convention on International Civil Aviation affirms a state's complete and exclusive sovereignty over its airspace. Foreign military aircraft or activities cannot enter another country's airspace for exercises unless permission is obtained. Article 3 of the Chicago Convention specifies that state aircraft, including military ones, may not fly over another state's territory without special authorization. The convention distinguishes between civil and state aircraft, with the latter exempt from certain scheduling rules but still subject to sovereignty principles. Therefore, extending an exercise zone into another state's airspace is unlawful.

Furthermore, military exercises must comply with the "due regard" principle to avoid interfering with civil aviation safety. Aerial exercises often involve issuing Notices to Airmen (NOTAMs) to designate temporary restricted areas, but foreign airspace requires express consent, and violations may trigger self-defense rights under UN Charter Article 51, which permits the sovereign state affected to intercept aircraft (subject to proportionality).

In recent years, the Philippines has employed various tactics to solidify its illegal territorial claims in the South China Sea, seeking to unilaterally expand its maritime entitlements. The delineation of this expansive military exercise zone fundamentally serves these objectives. By encroaching on disputed areas, Manila seeks to entrench its position through de facto control, disregarding the principles of peaceful resolution and mutual respect that underpin international law. This approach also ignores the historical and legal basis of China's sovereignty over features like Huangyan Dao, setting a dangerous precedent for regional disputes.

Particularly egregious is the inclusion of China's Huangyan Dao within the exercise zone, which constitutes a threat of force or the use of force. Under the UN Charter and customary international law, such actions are patently illegal and confer no legitimate rights. China, in response, retains its inherent right to self-defense. For national airspace, the Chicago Convention on International Civil Aviation (1944) affirms absolute sovereignty under Article 1, and military aircraft require explicit authorization to enter under Article 3. Incorporating foreign territory could be seen as an act of aggression under UN General Assembly Resolution 3314 (1974), justifying countermeasures, including self-defense under Article 51 of the UN Charter.

This incident follows the United States and the Philippines conducting their so-called 11th "maritime cooperative activity". On Jan 31, the South Sea Fleet of the Chinese People's Liberation Army conducted combat readiness patrols in the territorial waters, airspace, and surrounding areas of China's Huangyan Dao, sending a clear signal of its resolve to defend its sovereignty.

Since the so-called South China Sea arbitration ruling, the Philippines has persistently pushed for the "securitization" and "militarization" of the region. By crafting narratives of external threats and deepening security ties with external powers like the United States, Manila has transformed territorial and maritime delimitation disputes into security confrontations. This strategy aims to draw in foreign forces to counter China, all while advancing its unlawful territorial ambitions. The result is a deliberate erosion of the fragile peace that has characterized the South China Sea for years. Moreover, by flouting the limitations on military exercise zones—such as ensuring that they remain temporary, proportionate, and non-discriminatory—the Philippines risks further regional backlash, particularly from ASEAN partners who rely on stable sea lanes for trade.

The Philippines is orchestrating a multi-dimensional campaign—encompassing maritime operations, media propaganda, legal maneuvers, diplomacy and military actions—to inflame tensions in the South China Sea. Leveraging its role as ASEAN chair, Manila seeks to advance its private interests at the expense of regional harmony. Domestically, the Philippine armed forces, heavily influenced by the United States, maintain a hawkish stance on China, while civilian oversight remains weak. This internal discord reflects broader chaos and instability within Philippine politics and foreign policy, where anti-China rhetoric has become particularly vocal following recent diplomatic rebukes from the Chinese embassy in Manila.

Furthermore, the establishment of the military exercise zone, along with plans for joint drills with extra-regional states, reflects Manila's anxiety over the uncertainty of US policy. By engaging in military adventurism, the Philippines aims to underscore its purported "security role" and secure continued American backing. However, with China's growing capabilities to safeguard its rights and maintain stability in the region, such provocations are unlikely to succeed. Instead, they may amplify the risk of maritime mishaps and provide pretexts for interventions by the US, Japan, and other powers, further exacerbating regional militarization.

The sheer scale and duration of the Philippine exercise zone also disrupt the normal navigational and overflight freedoms of surrounding nations. It could also leverage intelligence-sharing cooperation between the US, Japan, and the Philippines against China. This not only jeopardizes the safety of South China Sea shipping lanes but also raises the specter of miscalculations and undermines the shared interests of regional states by fostering an atmosphere of tension. The responsibility for destabilizing peace lies squarely with the Philippines and its external backers.

Ultimately, the Philippines' unilateral actions and deep military entanglements with outside powers, directly challenges ASEAN's collective interests. These escalating provocations and militarization efforts are shattering the long-standing peace and stability in the South China Sea, fueling concerns among ASEAN nations about deteriorating regional security. Frequent large-scale exercises and rising military confrontations significantly elevate the likelihood of misjudgments and conflict, potentially dragging the entire region into turmoil and disrupting the peaceful environment essential for economic development.

In the coming months, as the Philippines assumes its ASEAN chairmanship, we may anticipate more manufactured incidents across maritime, media, and diplomatic fronts, alongside joint exercises with extra-regional partners. Yet, in the face of China's steadfast commitment to defending its legitimate rights and upholding regional peace, these efforts amount to little more than futile resistance. The future of the South China Sea hinges on dialogue and cooperation, not confrontation—a principle Manila would do well to heed before its actions irreparably harm the region.

Ding Duo is the director of the Center for International and Regional Studies, National Institute for South China Sea Studies.

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