Anchored in Law: The Philippines’ Legitimate Claim to Bajo de Masinloc

The Philippines’ claim to Bajo de Masinloc (Scarborough Shoal) rests on both historical legitimacy and the binding authority of international law. Centuries of cartographic evidence, corroborated by consistent acts of administration, establish continuity of title. Modern maritime law provides the decisive framework: under the United Nations Convention on the Law of the Sea (UNCLOS), entitlements to maritime zones and resources are clearly defined. Situated within the West Philippine Sea, the shoal lies approximately 220 KM (119–124 NM) west of Masinloc, Zambales, and nearly 500 NM from Hainan, China, firmly within the Philippines’ 200‑NM Exclusive Economic Zone (EEZ). This proximity underscores the arbitral tribunal’s 2016 ruling that the shoal is a “rock” under Article 121(3), entitled only to a 12‑NM territorial sea, with surrounding waters falling squarely within the Philippines’ EEZ.¹

This article situates the Philippines’ position within the UNCLOS regime, evaluating historical maps, state practice, comparative jurisprudence, and China’s activities. The analysis demonstrates that the Philippines’ claim is legitimate and firmly grounded in international law.

UNCLOS as Governing Framework

The UNCLOS provides the primary legal framework for maritime entitlements and dispute resolution. It establishes the scope of maritime zones, including territorial seas, EEZs, and continental shelves. UNCLOS clarifies that maritime entitlements derive from land features themselves, not from vague historical claims. This doctrinal principle was reaffirmed in the 2016 South China Sea Arbitration, where the tribunal held that China’s “nine-dash line” claim had no legal basis under UNCLOS.²

See also: The 2016 PCA Award in Philippines v. China: Clarifying Maritime Rights in the South China Sea.

Historical Foundations

• Murillo Velarde Map (1734) – The Carta Hydrographica y Chorographica de las Islas Filipinas, published in Manila in 1734, depicts “Panacot” (Bajo de Masinloc) as part of the Philippine territory off Zambales. As the first scientific and official map of the Philippines during the Spanish colonial period, its evidentiary value lies in its official provenance and pre-dispute character.³

• Spanish-Era and Colonial Maps – Subsequent maps—including the 1792 Malaspina expedition chart and the 1866 “Plano del Bajo Masingloc”—consistently depict Scarborough Shoal as part of the Philippine archipelago. While maps are generally treated as secondary evidence in international law, their corroboration by state practice and administrative acts enhances their probative value.⁴

Treaty Succession

• Treaty of Paris (1898) – The Treaty ceded the Philippine archipelago from Spain to the US, delineating boundaries through latitudinal and longitudinal coordinates. However, certain outlying islands, including Bajo de Masinloc, were not explicitly mentioned within the “Treaty Box.”⁵

• Treaty of Washington (1900) – To resolve ambiguities in the Treaty of Paris, the Treaty of Washington clarified that Spain relinquished all title to “any and all islands belonging to the Philippine Archipelago” outside the Paris lines. This provision encompassed islands historically administered as part of the Philippines, thereby reinforcing the inclusion of Bajo de Masinloc.⁶

• US–UK Convention (1930) – The 1930 Convention between the US and Great Britain further delimited boundaries between the Philippine Archipelago and North Borneo. Article III confirmed that islands north and east of the boundary line belonged to the Philippines. This treaty, binding under state succession, supports the Philippine claim to Scarborough Shoal.⁷

The South China Sea Arbitration

The Philippines initiated arbitration under UNCLOS Annex VII in 2013. In its 2016 award, the Permanent Court of Arbitration held that:

• While sovereignty over islands was outside its authority, questions of maritime rights and entitlements fell squarely within UNCLOS. This distinction allowed the case to proceed despite China’s objections.

• China’s claim of “historic rights” under the nine-dash line was ruled to have no legal basis. UNCLOS provides clear maritime zones and does not recognize vague historic claims beyond those limits.

• The Tribunal classified most reefs, shoals, and rocks as either low-tide elevations (no maritime zones) or “rocks” (only a 12‑nautical‑mile territorial sea). None qualified as “islands” capable of generating EEZs, drastically reducing China’s entitlements.

• China was held in violation of its UNCLOS duty to protect and preserve the marine environment. Large-scale reclamation and destructive fishing caused severe ecological damage, and the Tribunal emphasized that environmental obligations are binding.

• China unlawfully prevented the Philippines from exercising its EEZ rights, blocking fishermen at Scarborough Shoal and disrupting oil exploration at Reed Bank. These actions violated the sovereign rights of coastal states under UNCLOS.⁸

State Practice and Comparative Jurisprudence

International jurisprudence consistently prioritizes acts of administration and effective occupation over cartographic claims. The Philippines continues to reinforce its position through documented patrols, fisheries regulation, lighthouse maintenance, and legislative measures such as the Philippine Maritime Zones Act.⁹ These ongoing acts of state strengthen entitlement claims under UNCLOS, especially in the face of China’s de facto control since 2012 through coast guard and maritime militia deployments.

Tribunal precedents confirm this doctrinal weight:

• Pedra Branca (Malaysia/Singapore, ICJ 2008): Singapore prevailed due to the continuous administration of the Horsburgh Lighthouse, while Malaysia’s reliance on maps proved insufficient.¹⁰

• Minquiers and Ecrehos (France/UK, ICJ 1953): The Court favored the UK’s demonstrated authority—fishing regulation, tax collection, judicial acts—over France’s cartographic evidence.¹¹

• Ligitan and Sipadan (Indonesia/Malaysia, ICJ 2002): Malaysia succeeded based on regulatory measures such as turtle egg collection and lighthouse establishment, while Indonesia’s reliance on treaties and maps was inadequate.¹²

These precedents show that while maps and treaties provide historical legitimacy, sovereignty disputes hinge on effective occupation. For the Philippines, consistent and documented acts of administration are not optional but doctrinally necessary to reinforce its claim, particularly against China’s entrenched presence since 2012.

Chronology of China’s Activities at Bajo de Masinloc (2012–2026)

• 2012 Standoff and Seizure of Control – China seized de facto control of Scarborough Shoal after a confrontation with Philippine vessels, breaking a withdrawal agreement by deploying a PLA Navy ship. This marked the start of exclusionary practices, contravening UNCLOS principles of freedom of navigation and lawful use of the EEZ.¹³
• 2012–2025 Sustained Harassment – Following its takeover, China maintained a constant presence through coast guard and maritime militia patrols. Filipino fishermen were obstructed, and Philippine vessels were shadowed, violating UNCLOS provisions guaranteeing rights of navigation and resource use within the EEZ.¹⁴
• July–August 2025 Escalations – The Philippine Coast Guard reported an obstruction by a China Coast Guard vessel near the shoal. During the harassment, the CCG vessel collided with a PLA Navy warship in the vicinity of the PCG patrol. Chinese state media misrepresented the incident, portraying Philippine patrols as aggression, though Philippine authorities clarified that the collisions involved Chinese vessels themselves.¹⁵
• September 2025–2026 “Marine Reserve” and Propaganda Narrative – Beijing declared Scarborough Shoal a “protected marine reserve,” asserting jurisdiction within the Philippine EEZ in violation of UNCLOS. It then framed exclusionary tactics as environmental stewardship through the “National Nature Reserve” propaganda despite prior ecological damage from giant clam harvesting. Propaganda portrayed the shoal as a “traditional fishing ground” and joint Philippine–US patrols as provocations, aiming to delegitimize UNCLOS‑based entitlements.¹⁶
• December 2025–January 2026: Combat Patrols – PLA Southern Theater Command deployed warships, cutters, and H-6K bombers armed with YJ-12 anti-ship missiles, escorted by Su-35 fighters. These deployments raised concerns under international law, which prohibits the threat or use of force against the territorial integrity or political independence of any State.¹⁷
• January 12–13, 2026 Harassment Incident – A Filipino fishing boat (Prince LJ) was aggressively maneuvered against by PLA Navy and China Coast Guard vessels, forcing intervention by the PCG’s BRP Cape San Agustin. This exemplified China’s coercive tactics to exclude Filipino fishermen from their lawful EEZ.¹⁸

Conclusion

The Philippines’ position on Bajo de Masinloc rests on both law and geography. The 2016 South China Sea Arbitration confirmed that Scarborough Shoal is a “rock” under UNCLOS, generating only a 12-NM territorial sea, with the surrounding waters falling within the Philippines’ EEZ. Its proximity, 220 KM west of Masinloc, Zambales, within the West Philippine Sea, reinforces this entitlement and exposes the weakness of Beijing’s jurisdictional claims.

It is essential to distinguish sovereignty from entitlements. Although sovereignty over the shoal itself remains unresolved, the Philippines’ rights to fisheries and resources in the surrounding waters are already settled under UNCLOS. This doctrinal separation prevents confusion and ensures consistency with international law.

The dispute underscores enduring imperatives: to uphold UNCLOS and the arbitral award, to demonstrate effective occupation through patrols and regulation, and to work with allies to defend the rule of law. In the end, while history strengthens legitimacy, geography and UNCLOS-based doctrine provide the decisive foundation, showing why UNCLOS remains the enduring framework for maritime order in the West Philippine Sea and the broader South China Sea.

Footnotes

1. United Nations Convention on the Law of the Sea, Dec. 10, 1982, 1833 U.N.T.S. 3 [hereinafter UNCLOS]. ↩︎
2. The South China Sea Arbitration (Philippines v. China), PCA Case No. 2013-19, Award (July 12, 2016) [hereinafter Philippines v. China, PCA 2016 Award]. ↩︎
3. Carta Hydrographica y Chorographica de las Islas Filipinas (Pedro Murillo Velarde Map, 1734). ↩︎
4. See Malaspina Expedition Chart (1792) (on file with Museo Naval de Madrid, Hydrographic Collection); Plano del Bajo Masingloc (Commander E. Wilds, 1866) (on file with U.S. Hydrographic Office Records, National Archives). ↩︎
5. Treaty of Peace Between the United States of America and the Kingdom of Spain, U.S.–Spain, Dec. 10, 1898, 30 Stat. 1754, T.S. No. 343 (Treaty of Paris). ↩︎
6. Treaty Between Spain and the United States for Cession of Outlying Islands of the Philippines, U.S.–Spain, Nov. 7, 1900, 32 Stat. 1821, T.S. No. 345 (Treaty of Washington). ↩︎
7. Convention Between the United States and Great Britain Delimiting the Boundary Between the Philippine Archipelago and the State of North Borneo, U.S.–U.K., Jan. 2, 1930, 173 L.N.T.S. 38. ↩︎
8. Philippines v. China, PCA 2016 Award, ¶¶ 119–123, 207–278, 278–320. ↩︎
9. Republic Act No. 12064, Philippine Maritime Zones Act. ↩︎
10. Sovereignty over Pedra Branca, Middle Rocks and South Ledge (Malay./Sing.), Judgment, 2008 I.C.J. Rep. 12. ↩︎
11. Minquiers and Ecrehos (Fr./U.K.), Judgment, 1953 I.C.J. Rep. 47. ↩︎
12. Pulau Ligitan and Pulau Sipadan (Indon./Malay.), Judgment, 2002 I.C.J. Rep. 625. ↩︎
13. Philstar.com, China Broke 2012 Scarborough Shoal Deal by Sending Warship (Aug. 12, 2025). ↩︎
14. Philstar.com, PCG Reports China’s Latest Harassment Near Scarborough Shoal (17 Jul 2025). ↩︎
15. Inquirer.net, China Experts Weigh in on ‘News Blackout’ of Scarborough Collision (Aug. 18, 2025). ↩︎
16. Xinhua, China to Establish Huangyan Dao National Nature Reserve (Sept. 10, 2025). South China Morning Post, China’s Presence at Scarborough Shoal in South China Sea ‘Unprecedented’ in 2025: Report (Jan. 30, 2026). ↩︎
17. Naval News, China Sends Anti-Ship Bomber, Frigates to Scarborough Shoal (Oct. 3, 2025). ↩︎
18. Inquirer.net, First Chinese Harassment Incident of 2026 in Philippine Waters Logged at Scarborough Shoal (Jan. 13, 2026). ↩︎