Tuesday, October 7, 2025

In defense of the Philippine territorial claims over the Kalayaan (Spratly) group and related features (Scarborough / Bajo de Masinloc, etc.), focusing on the three treaties invoked (Paris 1898, Washington 1900, and the U.S.–U.K. (1930) boundary convention) plus supplementary legal arguments.

Below is a two-part response. First, a summary of the news article and its central claims. (West PH Sea: DFA cites Treaty of Paris to assert PH territorial rights | INQUIRER.net https://share.google/IKEIRO2Zz5F492ZaN)


Second, a legal-memorandum style analysis and defense of the Philippine territorial claims over the Kalayaan (Spratly) group and related features (Scarborough / Bajo de Masinloc, etc.), focusing on the three treaties invoked (Paris 1898, Washington 1900, and the U.S.–U.K. (1930) boundary convention) plus supplementary legal arguments.


I. Summary of the News Article

  • The Inquirer reports that on October 7, 2025, the Department of Foreign Affairs (DFA) of the Philippines publicly reaffirmed that the Philippines’ sovereign claims in the West Philippine Sea (i.e. parts of the South China Sea) rest in part on historic treaty bases, in particular the Treaty of Paris (1898).
  • The DFA maintains that the Kalayaan Island Group (KIG, Philippines’ internal name for its claim in the Spratly area) and Bajo de Masinloc (Scarborough Shoal) have long been part of Philippine territory as recognized under these treaties.
  • The DFA also refers to other treaties beyond Paris 1898 and Washington 1900, including a 1930 U.S.–Great Britain treaty (i.e. a boundary convention between the U.S. (as sovereign of the Philippines) and the U.K.), which it says “clearly and firmly state the extent of Philippine territory” and binds successor states (e.g. Malaysia, Brunei) to respect the boundaries recognized.
  • The DFA rejects interpretations by “some countries” that would narrowly read the Treaty of Paris as a final delimitation that excludes features like Scarborough Shoal or the Kalayaan group.
  • The DFA’s position is that Philippine sovereignty over these features is “incontrovertible and firmly founded on international law, legal principles, effective control, and recognition through international treaties and agreements.”

In short, the news conveys that the DFA is reasserting a treaty-based foundation for Philippine claims, pushing back against arguments that the 1898 treaty “box” is constraining, and invoking subsequent treaties (esp. 1900 and the 1930 U.S.–U.K. convention) to buttress its claims.


II. Legal Memorandum: Philippine Sovereign Claim over KIG / Spratlys / Scarborough / 


Legal Foundations of Philippine Sovereignty Claims over Kalayaan Group (Spratlys) and Related Features


Issue
Whether the Philippines has a valid and defensible claim of territorial sovereignty over the Kalayaan Island Group (Spratly features) and adjacent features such as Bajo de Masinloc (Scarborough Shoal), based on treaty bases (Paris 1898, Washington 1900, U.S.–U.K. 1930), subsequent state practice, and other international law principles.


Short Answer
Yes, the Philippines can mount a credible legal defense of sovereignty over the Kalayaan group and related features founded on (1) the successive cession treaties (Paris and Washington) that incorporate residual islands, (2) the 1930 U.S.–U.K. convention which delimits boundaries and affirms U.S. (hence Philippine) sovereignty over islands within the delimitation, (3) continuous and consistent exercise of sovereignty (effectivités) by the Philippines, and (4) the doctrine of succession and acquiescence of successor states. While counterarguments exist (especially from China), the treaty record combined with effective control and legal recognition offers a strong basis for the Philippine claim.

Below is a structured analysis.


A. Treaty Foundations


1. Treaty of Paris (1898) — The “Treaty Box”

  • The Treaty of Peace between the United States and Spain (December 10, 1898) is the foundational cession treaty through which Spain relinquished sovereignty over Cuba, Puerto Rico, Guam, and the Philippine archipelago to the United States.
  • Article III of the Treaty of Paris describes a territorial “box” by reference to specific meridians and parallels — a “line running … 118° to 127° E, then etc.” — which supposedly delimits “the archipelago known as the Philippine Islands” to be ceded to the U.S.
  • Critics argue that under that “box,” features lying west (or outside) of that boundary line (e.g. some Spratly features, Scarborough Shoal) were excluded from the cession. Some interpreting states assert that the 1898 treaty is a fixed outer boundary beyond which Philippine claims cannot pass.
  • However, the Philippines (via the DFA) and historically Philippine legal scholars argue that the Treaty of Paris was never intended by the parties as a final delimitation, but primarily as a cession of sovereignty over Spanish possessions in the archipelago, subject to clarifications or supplements.
  • Indeed, the Treaty of Paris itself includes a protocol (March 29, 1900) extending certain provisions (Article IX) pertaining to Spanish subjects’ nationality.

Thus, while the Treaty of Paris supplies a “framework box,” it is not airtight as a boundary limitation, especially when one considers subsequent clarifications.


2. Treaty of Washington (1900) — Clarification & Supplement (the “Pocket Treaty”)


  • To resolve ambiguities or misunderstandings about the cession of “outlying islands” lying outside the lines in the Treaty of Paris, Spain and the United States concluded a supplementary treaty on November 7, 1900: the “Treaty Between Spain and the United States for the Cession of Outlying Islands of the Philippines.”
  • The sole Article states that Spain “relinquishes to the United States all title and claim of title … to any and all islands belonging to the Philippine Archipelago, lying outside the lines described in Article III of the Treaty of Paris … and agrees that all such islands shall be comprehended in the cession of the Archipelago as fully as if they had been expressly included within those lines.”
  • Particularly, the treaty mentions “Cagayan, Sulu, Sibutu and their dependencies,” but its language is general and sweeping: it reaches all islands belonging to the Philippine archipelago outside the prior box.
  • In effect, this “clarificatory” instrument functions as a “pocket treaty” that expands the cession to include residual islands not covered by the geometric lines of the Paris treaty.
  • Philippine legal scholars and commentators (notably Justice Antonio Carpio) emphasize that this treaty must be read as a retroactive supplementation of the Paris cession, thereby incorporating many of the features of the Spratlys and Scarborough, assuming they qualified as “islands belonging to the Philippine Archipelago” under Spanish rule.
  • The U.S. government thereby treated the 1900 Treaty as confirming U.S. sovereignty (and hence future Philippine sovereignty) over residual and outlying islands beyond the treaty box.
  • Some external analyses affirm that the 1898 box was “supplemented retroactively” by the 1900 treaty.

Thus, under a legal reading respectful of pacta sunt servanda and ejusdem generis, the Treaty of Washington should be construed as expanding the cession boundary, not as a mere narrow addendum.


3. Convention between the United States and Great Britain (1930) — Delimitation vis-à-vis British Borneo


  • In the colonial era, North Borneo (Sabah) was under British protection. The Philippines (then U.S. territory) shared a maritime adjacency with North Borneo / British possessions across the Sulu and South China Seas.
  • To settle boundary issues and recognize sovereignty claims, the U.S. and the U.K. signed the “Convention Delimiting the Boundary between the Philippine Archipelago and the State of North Borneo” on January 2, 1930.
  • The convention (with later exchanges of notes in 1932) drew a boundary line between the Philippines and North Borneo. Importantly, Article III of the convention states that “all islands to the north and east of the said line … shall belong to the Philippine Archipelago.”
  • In other words, in delimiting the lateral boundary vis-à-vis North Borneo, the U.K. recognized that certain islands (even if lying outside the Paris box) fall to the Philippines by virtue of their position relative to that delimitation.
  • The Philippines today inherits that treaty régime as a successor state to U.S. sovereignty over those ceded Philippine archipelago territories.
  • This convention thus provides a complementary boundary confirmation by a third party (Britain), which is relevant especially vis-à-vis Malaysia (successor to British Borneo).
  • The Philippine DFA explicitly cites this 1930 treaty in the news report, contending that it “clearly and firmly state the extent of Philippine territory” and binds successor states (including Malaysia) to respect the boundary delimitation.

Thus, the 1930 U.S.–U.K. boundary convention reinforces the treaty foundation for Philippine sovereignty over islands lying north/east of the line, which plausibly include many of the claimed KIG / Spratly features (depending on charting).


B. Mapping, Historical Cartography, and Spanish Pre-condemnation


  • One critical piece is how Spanish-era cartography (particularly the 1734 Murillo Velarde map) depicted the Philippine archipelago. Philippine analysts rely on those maps to show that the Spratly features and Scarborough Shoal (Panacot in the old mapping) historically belonged to the “Las Islas Filipinas” conception under Spain.
  • The Murillo Velarde map is often used as a frame of reference to interpret what Spanish sovereignty considered “the Philippines” ante bellum.
  • If those maps depict the Spratly features and Scarborough Shoal as part of the Philippine domain, then the 1900 Treaty’s language “any and all islands belonging to the Philippine Archipelago” may be read to incorporate them.
  • Moreover, after 1898–1900, U.S. authorities (as successor to Spanish claims) adopted Spanish official maps and charts (e.g. the 1875 “Carta General del Archipélago Filipino”) and issued internal documents treating those features as part of U.S./Philippine territory.
  • In the 1928 Palmas (Miangas) arbitration, the U.S. (representing Philippine territory) invoked those Spanish and U.S. cartographic practices to judicial effect, illustrating that map-based claims have persuasive weight in boundary and sovereignty disputes.

Hence, historical cartography, when coherently linked to treaty texts, bolsters the Philippine interpretive construction of the treaties.


C. Effectivités, State Practice, and Recognition


Even if an adversary challenges a treaty reading, a robust sovereignty claim must be supported by effective exercise of authority (effectivités) and acquiescence or recognition by other states. The Philippines has several such arguments:


  1. Continuous administration and enforcement

    • The Philippines, since the mid-20th century, has taken steps to occupy, build, and enforce law on many features in the KIG / Spratly group (e.g. military outposts, lighthouse construction, resupply, coast guard patrols).
    • The creation of Presidential Decree 1596 (1978) formally asserted Philippine sovereignty over the Kalayaan group, defining the area and asserting jurisdiction over the seabed, subsoil, and airspace.
    • The Philippines has also protested incursions, maintained a presence, and engaged in resource exploitation (within claim) consistent with sovereign rights.

  2. Lack of persistent protest by other states

    • Over decades, competing claimant states (e.g. Malaysia, Vietnam) have not universally and consistently protested every single act of Philippine administration. This relative silence or intermittent protest weakens counterclaims.
    • The U.K., in its capacity as colonial power, having signed the 1930 convention that placed islands north/east of the delimitation under Philippine archipelago sovereignty, is bound by that recognition.
    • Successor states such as Malaysia, as successors to British North Borneo, derive their boundary recognition obligations from the 1930 treaty and its boundary placements.

  3. Integration into Philippine legal and constitutional order

    • The 1935 Philippine Constitution, and succeeding constitutions, have incorporated as part of the national territory the islands ceded under the 1898 and 1900 treaties, as well as treaty limits confirmed by the 1930 U.S.–U.K. convention.
    • Philippine statutes, regulations, and administrative acts treat those features as part of the national territory. This internal consistency is relevant under the doctrine of internal coherence in state practice.

  4. Recognition by third parties

    • Some third states or international instruments tacitly recognize Philippine claims (for instance, maps, diplomatic correspondence, statements of acquiescence, or silence).
    • The fact that the DFA feels confident citing the treaty bases against “misinterpretation” by other countries suggests the Philippines believes that external actors have contested narrow readings of the treaty lines.

These effectivités, combined with treaty bases, strengthen the Philippine sovereignty claim.


D. Counterarguments and Rebuttals


  1. China’s “historic rights” / nine-dash line

    • The principal counterclaim from China is based on historic maritime claims (nine-dash line), which lack explicit treaty foundation and run contrary to modern principles of territorial sovereignty and the 2016 Arbitral Tribunal ruling (PCA) which rejected China’s expansive historic rights claims insofar as they exceed entitlements under UNCLOS.
    • The Philippines can articulate that its sovereignty claims are grounded in treaty-based title, effective control, and recognition—superior to mere historic rights claims lacking contemporaneous neutral recognition.

  2. Rigid “box” interpretation of the Treaty of Paris

    • Opponents may argue that the geometric lines in the Treaty of Paris are binding outer limits of Philippine territory.
    • The Philippine defense, however, is that the Paris treaty was never intended as an immutable delimitation but as a cession of Spanish Philippines, subject to supplementation (e.g. by the Washington 1900 treaty). Indeed, the explicit supplemental wording of Washington 1900 must be construed to amend or enlarge the cession.
    • Treaties are to be interpreted in light of the object and purpose (Vienna Convention on the Law of Treaties, art. 31), and ambiguity in Article III of the Paris treaty invites reference to subsequent agreements (the Washington treaty) to clarify parties’ common intent.

  3. Interpretative limits of the Washington Treaty

    • Some critics might argue that the Washington treaty was limited to those outlying islands specifically mentioned (Cagayan, Sibutu, Sulu) and should not be stretched to embrace Spratlys or Scarborough.
    • The Philippine counter is that the plain language of the treaty is general (“any and all islands ... lying outside the lines …”) and must be understood in context with Spanish-era maps (Murillo Velarde, etc.). If the Spratlys and Scarborough were historically within the Spanish Philippines domain, they fall within “any and all islands” logic.
    • Moreover, the doctrine of ejusdem generis or generalia specialibus non derogant would require reading the specific named islands as exemplars, not limiting the general formula.

  4. Limitations of the 1930 U.S.–U.K. convention scope

    • Some may contend that the 1930 convention’s delimitation applies only to boundary issues vis-à-vis British Borneo (i.e. Sulu Sea, Southeast Philippines) and is irrelevant to features far west in the Spratly seas.
    • That is a valid point. The Philippine legal team must carefully map which Spratly features fall within the sectors north/east of the 1930 boundary line. Only those features that fall on the Philippine side of that line gain direct support from this treaty. For others lying further west, the treaty is less determinative.
    • However, even for western features lying outside the 1930 delimitation, the combined weight of the 1898 + 1900 treaties and effectivités still supports the claim.

  5. Acquiescence, contrary state practice, or protest by other states

    • Detractors might argue that other claimant states have consistently protested Philippine acts, which undermines effectivités.
    • The Philippine response is to scrutinize whether protests were timely, consistent, and sufficiently specific, and to demonstrate that certain administrative acts were either not protested or that protests lacked legal specificity. The burden lies on challengers to show effective counter-sovereign administration.
    • Furthermore, counterclaims must themselves bear treaty or customary foundations; mere protest does not displace superior title backed by treaty and continuous control.


E. Legal Arguments: Structure of the Philippine Case


Below is a schematic of how a Philippine legal brief or arbitration submission might organize its arguments:


  1. Title (legal basis of sovereignty)

    • The Philippines holds the superior treaty title to the claimed islands by virtue of the Treaty of Paris (as an initial cession) and the clarifying supplementary Treaty of Washington, which expanded the cession to residual islands not captured by the original treaty box.
    • In addition, the 1930 U.S.–U.K. convention confirms that islands north/east of the delimitation belong to the Philippine archipelago, further bolstering the treaty title against third-party claims.

  2. Interpretive Principles

    • Using the Vienna Convention on the Law of Treaties (or customary analogues), adopt the principle that treaties must be interpreted in light of their ordinary meaning, context, object and purpose, subsequent agreements, and relevant supplementary materials (Vienna Art. 31–32 analogues).
    • Where ambiguity arises, subsequent treaties (Washington 1900) and consistent practice should inform interpretation.

  3. Historical Evidence / Cartography

    • Introduce the Murillo Velarde 1734 map, Spanish-era charts, and internal Spanish administrative acts to demonstrate that key features (Spratly and Scarborough) were historically regarded within the Spanish Philippine domain.
    • Show how U.S. authorities, upon taking over, adopted Spanish maps and continued to treat those features as part of U.S. Philippines territory.

  4. Effectivités / State Practice

    • Document Philippine acts of occupation, administration, military presence, law enforcement, infrastructure, protests of intrusion, and continual assertion of jurisdiction over the features.
    • Counter or explain protests from other states; show that many Philippine acts occurred without effective protest, or that protests were weak, vague, or not maintained.

  5. Recognition and Succession

    • Show that the 1930 U.S.–U.K. convention binds Britain (and thus by succession Malaysia / British North Borneo entities) to the boundary framework recognizing Philippine islands.
    • Demonstrate that successor states (e.g. Malaysia) inherited those treaty obligations and cannot repudiate them unilaterally.

  6. Supremacy of Treaty Title over “Historic Rights” Claims

    • Emphasize that treaty-based sovereignty is a superior legal basis compared to competing historic maritime claims not grounded in treaties or recognized by third states.
    • If relevant, rely on the 2016 Arbitral Tribunal ruling (though China does not accept it) which clarified limits of historic rights under UNCLOS.

  7. Equitable and Practical Considerations

    • Highlight coherence of Philippine administration in ensuring maritime security, resource management, and regional stability.
    • Emphasize that recognition of Philippine sovereignty over KIG / Spratly features is consistent with stable maritime order and the rule of law.

  8. Remedy Sought & Relief

    • Request declaratory affirmation of Philippine sovereignty over the KIG / Spratlys / Scarborough.
    • Seek injunctions against incursions, demand withdrawal of foreign vessels, and request international recognition and enforcement.


F. Conclusion & Strategic Recommendations


In conclusion, the Philippine claim to the Kalayaan (Spratly) islands and associated features is defensible on solid treaty foundations (Paris 1898 + Washington 1900) supplemented by the 1930 U.S.–U.K. boundary convention, backed by historical cartography and sustained state practice (effectivités). While adversary claimants may dispute the precise geographic reach, the Philippines’ case is not merely aspirational but based on established legal doctrine.


Nevertheless, prudent diplomacy and careful mapping of each contested feature relative to treaty lines, coupled with rigorous documentation of administrative acts and protest history, will be critical in any future arbitration, negotiation, or court adjudication.


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Assisted by ChatGPT AI app, October 7, 2025.


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