The Spratlys are ours as per the Treaty of Washington

The Treaty of Washington of 1900 (the Treaty) was signed on November 7, 1900, and came into effect on March 23, 1901, when the Treaty ratifications were exchanged.  The Treaty sought to remove any ground of misunderstanding growing out of the interpretation of Article III of the 1898 Treaty of Paris by clarifying the specifics of territories relinquished to the US by Spain.

In consideration for certain explicit statement of relinquishments documented in the Treaty, the US agreed to pay to Spain the sum of one hundred thousand dollars ($100,000) within six (6) months after the exchange of Treaty ratifications. (Wikipedia)

News had just recently came out that the Government of the Republic of the Philippines (GRP) discovered that, under the explicit terms of the Treaty, the Spratlys are, in fact, part of the territories ceded by Spain to the US under the Treaty of Paris.  The GRP will present this newly-discovered information to UNCLOS as additional evidence to support her claim over the Spratlys (as well as other territories within her 200-mile EEZ).

This is a very major development on the Spratlys disputes.

The Philippines now have a legal basis to claim the entire Spratlys.  And the islands of the Spratlys can now be used as baselines to measure the territorial sea and EEZ boundaries of the Philippines.

More importantly, the US is now legally a former owner of the Spratlys, and the Spratlys are now legally part of the territories donated by the US to the GRP in 1946.

Should any third party (e.g. China) attempt to dispossess the GRP of such donation, the US will now have the legal basis to intervene.

With the full might of the US Military Establishment, if necessary.