Watch more News on iWantTFC

MANILA (UPDATED)— The Chinese coast guard's use of a military-grade laser on a Philippine vessel last week constituted an armed attack and could be used by Manila to invoke its Mutual Defense Treaty with the United States, a former Supreme Court justice said Tuesday.

Former Supreme Court Associate Justice Antonio Carpio said that while the laser caused only temporary blindness among the Philippine ship's crew, it was "still a weapon or an arms" that qualifies under the Mutual Defense Treaty.

"The use of lasers that causes permanent blindness is a prohibited weapon under the 1998 Protocol on Blinding Laser Weapons to which China and the Philippines are parties," he said in a statement.

"Laser weapons can either cause permanent or temporary blindness. If it causes permanent blindness, the laser weapon is outlawed and cannot be used as a weapon by militaries. If it causes only temporary blindness, it can be used as a weapon by militaries."

• Marcos summons Chinese envoy over 'increasing intensity of actions' vs Pinoy fishers, PCG

But Carpio said Manila should coordinate first with the US for "a joint statement that future use by Chinese coast guard vessels of laser weapons on [Philippine] public vessels or aircraft will trigger the operation" of the treaty.

The United States on Monday criticized China's latest aggression against a Philippine coast guard vessel in the disputed South China Sea, saying the Chinese coastguard's "conduct was provocative and unsafe."

"The United States stands with our Philippine allies in the face of the People's Republic of China Coast Guard’s reported use of laser devices against the crew of a Philippine Coast Guard ship," State Department spokesperson Ned Price said.

The former justice also said that Beijing's new law that authorizes its coast guard vessels to use whatever force is necessary to enforce China’s nine-dash line claim, which an international court invalidated, violates the UN Charter.

That charter, he said, "outlaws the use of force to settle disputes between states, and mandates that all such disputes be settled peacefully thru negotiation, mediation, arbitration or other peaceful means."

• PCG says China laser light use already 'second time'
• Philippines files diplomatic protest over China's use of laser lights on PCG ship

—with a report from Agence France-Presse

Watch more News on iWantTFC