Senior Associate Justice Antonio Carpio rejected a proposal for the Philippines and China to conduct joint military drills in the West Philippine Sea, saying this could be seen as an implied admission that the Philippines' sovereign rights in the area are not secure.
Carpio said it is "ironic" for the Philippines to have joint patrols with China in the area because Beijing is claiming ownership of the West Philippine Sea, unlike in Benham Rise, where it has no claims.
"Since China claims the West Philippine Sea, it will be strange for us to agree that they patrol that area with us because when we allow it, that might be an implied admission that our sovereign rights are not that secure or firm," he said in an interview with ANC's Headstart.
Instead, Carpio is in favor of joint patrols with the United States, with whom the Philippines has a mutual defense treaty and is the only country that "has offered joint patrol."
After a Chinese warship docked in Davao City, President Rodrigo Duterte said China can have joint military drills with the Armed Forces of the Philippines in Mindanao particularly the Sulu Sea to combat the kidnapping activities of terror group Abu Sayyaf.
His national security adviser, former military chief Hermogenes Esperon Jr., expressed support for this idea, but said the proposal will still have to be studied as joint patrols can only be carried out under the guidance of a formal treaty.
Carpio also advised Duterte to be more careful in his pronouncements as his administration tries to improve the country's ties with Beijing. He said Duterte's words could easily be misconstrued as waiving the people's sovereignty.
"The other side could argue that that is the implication, so we should be very careful, we have to weigh very carefully what declarations we make before the world," he said.
"There is a principle in international law that statements of the President, unilateral statements can bind the country because as far as the international is concerned, your head of state binds your country whenever he speaks," he said.
Carpio, who was instrumental in Manila's case against Beijing before the Permanent Court of Arbitration in The Hague, said if a government official waives the country's sovereign rights as was awarded by the international tribunal, "that would be betrayal of public trust."
"If you are no match for China, we don’t have to waive it. You can insist, even if you cannot physically get it, but you must keep on insisting because if you waive it, it is gone forever," he said, noting that China "will never give it back."
"We are not the final judge of whether we have waived it or not. It could be an international tribunal," he added.