China's Legal Campaign Deepens the South China Sea Dispute With the Philippines

New laws, sharper confrontations

The Philippines enacted two maritime laws in November 2024 to define its rights at sea and establish a framework for routes through its archipelagic waters. China answered with straight baselines around Scarborough Shoal, stronger claims that Philippine operations were unlawful, and increasingly forceful patrols. In September 2025, Beijing added another administrative measure: a proposed nature reserve covering thousands of hectares of the shoal's coral reef.

By November 15, 2025, these steps had become part of a wider contest over who writes the rules, who enforces them and who can use disputed waters. Coast guard blockades, groups of maritime militia boats and aerial harassment operate alongside laws, diplomatic statements and conservation plans. Beijing presents itself as maintaining order. Manila says China is using legal language to justify interference with Philippine rights.

This approach is often called lawfare: using laws and legal arguments to advance strategic goals. In the South China Sea, its purpose extends beyond defending a position in court. A government can create rules, repeatedly describe its actions as lawful and then enforce those rules at sea, pressing other countries to accept its authority or risk a confrontation.

The central legal reference is the United Nations Convention on the Law of the Sea, known as UNCLOS. Both China and the Philippines are parties to it. The convention sets rules for maritime zones, resources and navigation, but the two governments disagree sharply about its application and China's claims based on historic rights.

The dispute connects technical legal questions with immediate risks for fishers, researchers, coast guard crews and aircraft. A line drawn on a map can become the stated reason for blocking a boat, restricting fishing or ordering a patrol to leave.

Why Beijing is challenging Manila's legal position

China portrays the Philippines as a provocateur whose maritime laws and patrols destabilize the region. Describing Philippine conduct as unlawful serves several purposes: discrediting Manila before domestic and international audiences, consuming its resources through legal disputes and supplying a justification for tougher Chinese enforcement.

Beijing's approach does not depend on winning a courtroom judgment. Repeated statements, domestic statutes and administrative decisions create a record of Chinese claims. Patrols then seek to make those claims part of everyday life at sea, establishing a new normal while other governments weigh the risks of resisting.

Maritime lawfare can involve national laws asserting jurisdiction beyond what other countries accept, public arguments designed to shape perceptions and international filings challenging rival claims. Jurisdiction means the authority to apply laws and take enforcement action in a particular place.

Chinese coast guard ships cite Chinese law when blocking Philippine resupply missions. Maritime militia boats appear as civilian fishing vessels while operating alongside enforcement efforts. Diplomatic notes and public statements describe rival governments as rule breakers, while pressure on the water changes the conditions under which those governments can operate.

Manila's response centers on UNCLOS and the 2016 arbitration award in its case against China. The tribunal rejected historic rights claims that conflict with the convention within another state's exclusive economic zone. China rejected that award and continues to assert its claims.

What the Philippine maritime laws do

The Maritime Zones Act, or MZA, defines the Philippines' territorial sea, contiguous zone, exclusive economic zone and continental shelf using UNCLOS definitions. These zones involve different rights: authority over territorial waters, specified enforcement powers farther out, and rights over resources in the exclusive economic zone and seabed.

The MZA states that the Philippine exclusive economic zone, commonly called the EEZ, extends up to 200 nautical miles from its baselines. Baselines are the reference lines from which maritime distances are measured. Where Philippine zones overlap with those of neighboring countries, their boundaries remain subject to delimitation, the process of agreeing where one country's zone ends and another begins.

The act also incorporates findings from the 2016 arbitration. Those findings include the classification of certain South China Sea features as rocks or low tide elevations that cannot generate an EEZ of their own. They also establish that historic rights claims cannot override another state's EEZ rights under UNCLOS.

The Archipelagic Sea Lanes Act, or ASLA, creates a framework for designating passage routes through Philippine archipelagic waters. These are waters within the island groups that form the country. The law concerns foreign ships and aircraft passing through them, with safe and continuous passage remaining central to the arrangement.

Manila's decisions about routes and conditions will affect where foreign military and coast guard vessels travel, how close they pass to sensitive areas, and how Philippine authorities apply safety and environmental rules. China's movements near Luzon and through Philippine archipelagic waters suggest an effort to influence those decisions by making particular routes appear routine.

How the dispute developed

The present confrontation brings together an arbitration award, coast guard legislation, Philippine maritime statutes and Chinese administrative measures adopted over several years. Each step adds another layer to arguments already being tested by patrols and encounters at sea.

• 2016: The tribunal in the Philippines' arbitration against China rejected historic rights claims conflicting with UNCLOS and ruled on the legal status of disputed maritime features.
• Since 2019: Governments have submitted a stream of diplomatic notes setting out their positions on maritime zones, historic rights and the status of features.
• 2021: China's Coast Guard Law introduced powers involving enforcement and the use of force in waters Beijing considers under its jurisdiction.
• June 2024: China issued administrative enforcement procedures, known as Order number 3, allowing detention for 30 days, or 60 days in complex cases.
• November 2024: The Philippines enacted the Maritime Zones Act and Archipelagic Sea Lanes Act. Within weeks, China declared straight baselines around Scarborough Shoal.
• Early 2025: Chinese ships cut across a Philippine vessel's bow, then used water cannon against and sideswiped a Philippine research boat.
• September 2025: Chinese authorities announced plans for a nature reserve at Scarborough Shoal.

The sequence shows how legal measures and operational pressure have advanced together. Philippine legislation clarified Manila's position; Chinese measures asserted competing authority; ships and aircraft continued to confront one another in the same contested areas.

Why the Scarborough baselines matter

Scarborough Shoal lies within the Philippines' EEZ, near major shipping routes and close to Luzon. The 2016 tribunal classified it as a rock, meaning it cannot generate an EEZ of its own, and recognized traditional fishing access for fishers from both China and the Philippines.

China's declaration of straight baselines around the shoal supplies a legal argument for tighter control. Straight baselines connect selected points rather than following every bend of a coastline. UNCLOS permits them in limited settings, such as deeply indented coasts or coasts fringed by islands.

Applying that method to an isolated maritime feature, then treating the enclosed waters as internal waters, is widely viewed as inconsistent with UNCLOS. Internal waters carry a stronger claim of national control than the surrounding maritime zones.

Beijing's declaration did not change the shoal's legal status recognized by most states. It nevertheless gave Chinese authorities another basis for saying that Philippine movements violated Chinese law and that enforcement measures were necessary.

Manila, supported by many governments, rejects those claims as lacking a basis in UNCLOS. Scarborough has consequently become a place where competing legal positions meet practical restrictions on patrols and fishing.

A nature reserve becomes another point of conflict

Chinese authorities announced the Scarborough nature reserve plan in September 2025. It would cover thousands of hectares of coral reef and be situated near the lagoon entrance. Beijing presented the measure as environmental protection; Philippine officials described it as an attempt to secure administrative control and squeeze out Filipino fishers.

Eduardo Año, the Philippines' national security adviser, condemned the proposal, calling it a mask for occupation. He described the plan as:

patently illegal

Año said the conservation measure was a pretext paving the way for eventual occupation and warned that Manila would not accept it.

Marshall Louis Alferez, a Department of Foreign Affairs assistant secretary responsible for maritime and ocean affairs, said Scarborough was an integral part of Philippine territory. He maintained that only the Philippines could establish protection areas there and that Manila had the authority to manage environmental protection within its waters.

The reserve plan combines conservation language with an assertion of administrative authority. Domestic rules and signage can make a claim tangible, leaving other users facing a choice between accepting restrictions and challenging the authorities enforcing them. Coupled with baselines, patrols and air sorties, the proposal forms part of Beijing's effort to strengthen control around the shoal.

Confrontations put maritime safety under strain

Second Thomas Shoal, Sabina Shoal and Scarborough Shoal have been prominent locations for increasingly dangerous encounters. Philippine vessels have reported collisions, aggressive close approaches and repeated water cannon blasts during Chinese enforcement operations.

Near Sabina Shoal in 2024, a Philippine coast guard ship and a Chinese vessel collided during what Manila described as a routine mission. In early 2025, Chinese ships crossed the bow of a Philippine vessel before using water cannon against and sideswiping a Philippine research boat.

In another incident, two Chinese vessels rammed each other while trying to block a Philippine ship. The collision illustrated the intensity and confusion that can develop when several vessels maneuver close together. A senior Philippine coast guard official also said a recent water cannon strike badly damaged a fishing boat and injured a crew member with flying glass.

The relevant safety framework is the 1972 Convention on the International Regulations for Preventing Collisions at Sea, usually called COLREGS. Both governments accept these rules, which guide vessels on avoiding collisions.

The tribunal in the Philippines' arbitration stressed that COLREGS must take priority over law enforcement requirements when vessels face a collision risk. Encounters around the Spratlys and Scarborough show a pattern at odds with those rules, including dangerous crossings ahead of other ships, close approaches and water cannon use that increases collision risks.

Geng Yu, a China Coast Guard spokesman, defended Chinese action after confrontations near Sabina Shoal. He said a Philippine vessel:

illegally entered

Geng described Chinese units as having:

took control measures… in accordance with the law.

Philippine officials counter that Chinese ships and aircraft are operating in areas where Manila holds sovereign rights under UNCLOS. They describe the conduct as intimidation.

Aircraft face pressure above disputed waters

Philippine officials described a Chinese military helicopter hovering within about 10 feet of a Philippine fisheries plane near Scarborough Shoal and ignoring radio calls. They also described Chinese aircraft shadowing or harassing Philippine patrols over the Spratlys.

Such encounters raise immediate safety concerns because aircraft operating extremely close together have little room to respond to an unexpected movement. The actions run against basic aviation safety norms and guidance associated with the International Civil Aviation Organization.

China presents many of its maritime and aerial actions as lawful control in areas it considers under Chinese jurisdiction. Manila's position is that the same operations interfere with Philippine rights and expose personnel to avoidable danger.

Sea lanes and the concern over persistent patrols

Archipelagic sea lanes involve a specialized UNCLOS passage regime. Foreign ships and aircraft using them are entitled to continuous and speedy passage, similar to transit passage through straits used for international navigation.

An archipelagic state can establish routes, traffic separation arrangements and safety rules. It cannot restrict transit for political reasons or require prior permission. Manila therefore has to account for both navigational rights and its own safety and security concerns when developing its sea lane arrangements.

Chinese vessels' regular movements may become part of that argument. A sustained presence off Zambales, deeper movements into Philippine waters and parallel tracks aligned with possible future lanes can create a record of use. Beijing could then cite those tracks as normal and widely used routes when pressing for their inclusion or for conditions favorable to Chinese operations.

Philippine defense officials have described Chinese ships along routes that could become official sea lanes as:

loitering with intent

The concern is that repeated movements help normalize Chinese transit patterns before Manila completes its arrangements. Persistent patrols near Luzon, combined with administrative measures around Scarborough, give Beijing several ways to assert a presence while describing its actions as lawful administration or safety measures.

What the 2016 award settled

The 2016 arbitral award is final under UNCLOS procedures. It held that China's claimed historic rights within the nine dash line have no legal effect inside another state's EEZ. The nine dash line is the map marking associated with China's expansive South China Sea claims.

The tribunal also determined that none of the Spratly features can generate an EEZ and that Scarborough is a rock without an EEZ of its own. It found that China interfered with traditional fishing at Scarborough and unlawfully prevented Philippine hydrocarbon exploration, meaning exploration for oil and gas.

Sovereignty over rocks and reefs remained outside the tribunal's decision. The award addressed maritime rights and the legal status of features, while ownership disputes continued.

Since 2019, diplomatic notes submitted by governments have clarified positions on historic rights, maritime zones and disputed features. Sometimes described as a battle of notes, this process has narrowed the lines of disagreement without resolving ownership.

United States Freedom of Navigation Operations and transits by partner countries support navigational rights and keep the legal issues in view. Their effect on behavior remains debated. European scholars have urged Southeast Asian claimants to keep their claims aligned with UNCLOS and pursue law and diplomacy. They have also urged the United States to ratify UNCLOS to strengthen its position.

China's coast guard powers raise the stakes

China's 2021 Coast Guard Law permits the use of force against foreign government ships in waters Beijing considers under its jurisdiction. It also authorizes enforcement in ambiguously defined areas, including waters beyond those other states accept as Chinese under UNCLOS.

The June 2024 administrative enforcement procedures, often called Order number 3, allow commanders to detain foreign vessels and personnel for 30 days, or 60 days in complex cases. The jurisdiction to which those powers apply is not clearly defined.

For Manila, the concern is that Philippine service members, scientists or fishers could be detained inside the Philippine EEZ under a unilateral Chinese interpretation of the law. The longer detention period is twice the shorter one, increasing the potential disruption to crews and missions.

Following the regulation, the China Coast Guard assumed a more direct role around Second Thomas and Sabina, displacing maritime militia in some operations. That shift makes state responsibility easier to identify while increasing the danger of a confrontation between government vessels.

The coast guard laws, public messaging and Scarborough reserve proposal work together as a set of measures asserting governance. Beijing seeks acceptance of rules written in China, while Manila challenges both their legal basis and their application at sea.

How Manila and its partners can respond

The Philippines can continue aligning domestic laws with UNCLOS, publish detailed sea lane regulations and document Chinese actions that conflict with the convention. Radar data, radio logs and video can help establish patterns involving collision rules and aviation safety.

Philippine agencies have become more active in releasing imagery of encounters and filing diplomatic protests. Public incident records and legal explanations challenge attempts to present disputed enforcement as routine administration.

Partner governments can support lawful Philippine operations in the EEZ, conduct presence operations affirming navigational rights and coordinate protests citing specific UNCLOS provisions. Where possible, bringing disputes before international bodies keeps legal claims under scrutiny, even when enforcing decisions is difficult.

Governments in Asia and Europe can continue submitting United Nations notes rejecting expansive historic rights claims and clarifying maritime positions. Technical assistance to Southeast Asian coast guards and fisheries agencies can improve incident documentation and lawful procedures.

Economic and trade measures tied to particular breaches of international law are another option for governments to examine carefully. Regional training in evidence collection, prosecution of maritime crimes and environmental monitoring can also improve accountability.

The United States has reiterated that attacks on Philippine armed forces, public vessels or aircraft in the Pacific, including the South China Sea, would trigger mutual defense commitments. Japan, Australia and European partners have increased maritime engagement and capacity building. Such cooperation aims to deter miscalculation and support management of disputes without coercion.

What to Know

• The Philippines enacted the Maritime Zones Act and Archipelagic Sea Lanes Act in November 2024 to define maritime rights and establish a passage framework.
• China responded with Scarborough baselines and, in September 2025, a nature reserve plan covering thousands of hectares.
• The 2016 award rejected historic rights conflicting with UNCLOS and found that Scarborough and the Spratly features cannot generate their own EEZs.
• Collisions, water cannon attacks and close aerial encounters have increased risks to Philippine crews.
• Chinese detention procedures allow 30 days of detention, extended to 60 days in complex cases, in waters Beijing claims as its jurisdiction.
• Persistent Chinese vessel movements may influence arguments over future Philippine archipelagic sea lanes.
• Manila's response options include legal alignment, transparent incident records, coordinated diplomacy and cooperation with partners.