Treaties are formal, legally binding agreements between States or international organizations. 

In the Philippines, a treaty becomes domestically effective only after Senate concurrence, pursuant to Article VII, Section 21 of the 1987 Constitution. The constitutional design creates a two-step process: 

(1) the President negotiates and signs; 

(2) the Senate concurs by a two-thirds vote. 

Without Senate concurrence, a treaty—no matter how important internationally—has no binding force in Philippine law.

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High-yield in Public International Law and Political Law. Frequently tested through treaty vs. executive agreement distinctions, Senate concurrence requirements, and traps assuming presidential signature alone is enough.

Pimentel v. Office of the Executive Secretary, G.R. No. 158088, July 6, 2005 (Supreme Court; Lawphil).

Senator Pimentel questioned the constitutionality of the Japan-Philippines Economic Partnership Agreement (JPEPA), arguing that it could not bind the Philippines without Senate concurrence. 

The Supreme Court agreed, holding that treaties require Senate concurrence to become valid and enforceable domestically. Until the Senate acts, a signed treaty remains ineffective in Philippine law.

🥜 A treaty binds the Philippines domestically only after Senate concurrence—presidential signature alone is insufficient.

Bayan Muna v. Romulo, G.R. No. 159618, February 1, 2011 (Supreme Court; Lawphil).

The case challenged the Mutual Logistics Support Agreement (MLSA) with the United States, claiming it required Senate concurrence. 

The Supreme Court ruled that the MLSA is an executive agreement, not a treaty, because it merely implements existing agreements, particularly the Visiting Forces Agreement (VFA), which had already received Senate concurrence. As such, no additional Senate approval was required.

🥜 Executive agreements that implement existing treaties or laws do not require Senate concurrence—only treaties creating new obligations do.