SUBJECT: The Rule on ‘The Incorporation Clause’ vs ‘The Transformation Method’

I. Introduction

This memorandum provides an exhaustive analysis of the two principal doctrinal approaches governing the relationship between international law and municipal law within the Philippine legal system: the incorporation clause and the transformation method. The inquiry centers on the constitutional and jurisprudential framework that determines how customary international law and treaties become part of the law of the land and are enforceable in domestic courts. The resolution of this issue is critical for legal practitioners in matters involving human rights, diplomatic immunity, extradition, and the enforcement of international arbitral awards.

II. Statement of Issues

What is the doctrinal basis and legal effect of the incorporation clause under the Philippine Constitution?

What is the doctrinal basis and legal effect of the transformation method under the Philippine Constitution and statutory law?

How do Philippine courts apply these doctrines to customary international law and treaties, respectively?

What are the practical legal consequences of the distinction between these two doctrines in domestic litigation?

How does the Philippine approach compare with other jurisdictions?

III. The Incorporation Clause: Doctrine and Application

The incorporation clause is enshrined in Section 2, Article II of the 1987 Constitution, which states: “The Philippines renounces war as an instrument of national policy, adopts the generally accepted principles of international law as part of the law of the land and adheres to the policy of peace, equality, justice, freedom, cooperation, and amity with all nations.”
This clause operates as an automatic incorporation of generally accepted principles of international law (GAPIL) into Philippine law without the need for legislative enactment. The Supreme Court has consistently held that this refers primarily to customary international law. Once a norm achieves the status of customary international law—evidenced by state practice and opinio juris—it is automatically part of Philippine law, provided it is not contrary to the Constitution or statutory enactments. Courts can directly apply and enforce these principles. Landmark cases such as Secretary of Justice v. Lantion and Republic v. Sandiganbayan have invoked this clause to apply principles of international law on due process and the state immunity from suit.

IV. The Transformation Method: Doctrine and Application

In contrast, the transformation method requires that international law, particularly treaties and conventions, undergo a domestic legislative process to become enforceable as municipal law. This is derived from Section 21, Article VII of the Constitution: “No treaty or international agreement shall be valid and effective unless concurred in by at least two-thirds of all the Members of the Senate.”
Under this doctrine, a treaty, even if signed by the Executive, does not become part of Philippine law until the Senate gives its concurrence. Furthermore, for the treaty to be enforceable in domestic courts, its provisions often require implementing legislation, especially if they create crimes, impose taxes, or appropriate public funds. The treaty is thus “transformed” into local statute. The case of Tanada v. Angara affirmed this process, stating that the Senate’s concurrence “ensures that the other branches of government are bound to comply with Philippine treaty obligations.”

V. Key Jurisprudential Delineation

The Supreme Court has drawn a clear distinction between the application of the two doctrines. In Bayan v. Zamora, the Court held that the Vienna Convention on the Law of Treaties, while a treaty itself, codifies customary international law and its provisions on treaty interpretation may be applied under the incorporation clause. The seminal case of Kuroda v. Jalandoni early established that principles of international law (in that case, the laws of war) are received as part of the law of the nation. Conversely, in Pharmaceutical and Health Care Association of the Philippines v. Duque III, the Court ruled that the provisions of the WHO International Code of Marketing of Breast-milk Substitutes, being part of an unratified convention, had no binding effect without local legislation. The doctrine of pacta sunt servanda is applied to treaties, but its domestic enforceability hinges on the transformation method.

VI. Hierarchy and Conflict of Norms

A critical sub-issue is the hierarchy of norms when international law and domestic law conflict. The Constitution is the supreme law of the land. A customary international law principle incorporated under Article II, Section 2 must yield to a constitutional provision. Similarly, a treaty that has received Senate concurrence has the same status as a national statute; it is not superior to an act of Congress. The rule of lex posterior derogat priori (a later law repeals an earlier one) applies in conflicts between a treaty and a statute. However, the Supreme Court, in cases like Republic v. Sandiganbayan, has emphasized the policy of harmonization, construing domestic law in a way that does not violate international law obligations.

VII. Comparative Analysis Table

The following table summarizes the core distinctions between the two doctrines as applied in Philippine law.

Aspect	The Incorporation Clause	The Transformation Method
Source of Law	Customary International Law (GAPIL)	Treaties, Conventions, International Agreements
Constitutional Basis	Article II, Section 2 (Declaration of Principles)	Article VII, Section 21 (Executive Department)
Domestic Legal Process	Automatic incorporation; no legislative act required.	Requires Senate concurrence; often requires implementing legislation.
Role of the Judiciary	Courts can directly identify and apply GAPIL.	Courts can only apply a treaty after it has undergone the political process; they interpret but cannot create enforceability.
Primary Legal Effect	Makes customary international law directly applicable in domestic courts.	Makes treaty law part of domestic law, giving it the force and effect of a statute.
Hierarchy	Subordinate to the Constitution and possibly to statutes.	Equal to a statute; subject to the lex posterior rule.
Example in Philippine Jurisprudence	Application of the principle of state immunity from suit (Republic v. Sandiganbayan).	Application of the Visiting Forces Agreement (Bayan v. Zamora) or the Rome Statute (requires domestic legislation for crimes).

VIII. Practical Legal Consequences

The distinction has profound practical implications. In litigation, a party invoking a rule of customary international law (e.g., a human rights norm) can ask the court to take judicial notice of it under the incorporation clause. In contrast, a party invoking a treaty must first prove its validity by presenting the official gazette publication showing Senate concurrence. For lawyers drafting pleadings, citations to international law must be carefully sourced to the correct doctrine. Furthermore, the government’s international liability before bodies like the International Court of Justice or UN treaty bodies may arise from a failure to incorporate or transform its obligations, as seen in the aftermath of the Permanent Court of Arbitration ruling in Republic of Philippines v. People’s Republic of China.

IX. International Comparative Perspective

The Philippine system is dualistic in its treatment of treaties, requiring transformation, but monistic in its treatment of customary international law, accepting automatic incorporation. This hybrid model contrasts with purely monistic states (e.g., the Netherlands) where approved treaties are directly applicable, and strictly dualistic states (e.g., the United Kingdom) where even customary international law is subject to judicial adoption rather than constitutional mandate. The United States is similar to the Philippines, with customary international law being part of federal common law (the Charming Betsy canon) and treaties requiring Senate advice and consent, though self-executing treaties are directly applicable.

X. Conclusion and Recommendations

The Philippine legal system employs a bifurcated approach: the incorporation clause for generally accepted principles of international law (customary law) and the transformation method for treaty law. This framework ensures respect for international law while safeguarding democratic legislative processes. For legal practice:

Always ascertain the source of the international law norm being invoked—whether it is customary or conventional.

For customary international law, prepare evidence of its status as a GAPIL (state practice and opinio juris) for submission to the court under the incorporation clause.

For treaties, verify and cite the Senate resolution of concurrence and any relevant implementing legislation; do not assume direct applicability.

In case of an apparent conflict between an international law norm and domestic law, advance arguments based on the constitutional hierarchy and the principle of harmonious construction.

A clear understanding of this dichotomy is essential for effective advocacy in cases with transnational dimensions.