US Reaffirms Defense Commitment to Philippines. What Does That Mean?

According to the Philippines Department of Foreign Affairs, the U.S. government has recently re-affirmed its obligations to defend the Philippines under the 1951 Mutual Defense Treaty.  This is a particularly sensitive time to re-affirm this commitment, given the ongoing tensions between the Philippines and China in the South China Sea.

But what exactly is the U.S. committing to here? Would the U.S. actually feel obligated to defend Filipino claims to disputed islands and territories in the South China Sea? Let’s go to the text of the treaty:

Article IV

Each Party recognizes that an armed attack in the Pacific Area on either of the Parties would be dangerous to its own peace and safety and declares that it would act to meet the common dangers in accordance with its constitutional processes. Any such armed attack and all measures taken as a result thereof shall be immediately reported to the Security Council of the United Nations. Such measures shall be terminated when the Security Council has taken the measures necessary to restore and maintain international peace and security.

Article V

For the purpose of Article IV, an armed attack on either of the Parties is deemed to include an armed attack on the metropolitan territory of either of the Parties, or on the island territories under its jurisdiction in the Pacific or on its armed forces, public vessels or aircraft in the Pacific.

This seems to include any attack on Filipino vessels in the South China Sea.  I don’t think there is a clear obligation to intervene, but it could certainly help legalize US intervention (under international law) in favor of the Philippines.  Notice how the U.S. is committed only to “act to meet the common dangers in accordance with its constitutional processes.”  I think that could mean a unilateral presidential action, depending on your reading of the US Constitution’s processes for warmaking.  In any event, it is a non-trivial guarantee, if a bit fuzzy, and China should beware.