As Manila prepares to take legal action against Beijing over its alleged environmental destruction in the South China Sea, Filipino fishermen have vowed to retaliate against an order by China to detain any foreign nationals for trespassing in the waters by kidnapping Chinese nationals in the Philippines.

While analysts said the Philippine government’s legal action could be successful, they warned Beijing would likely respond with countermeasures against Manila and its people.

“Expect China to retaliate with restrictive trade measures, harassment of Filipino workers in China and more serious bullying in the disputed areas,” Edmund Tayao, a political analyst and professor at the San Beda Graduate School of Law in Manila, told This Week in Asia.

On Monday, the Philippines accused Beijing of destroying the marine environment around the Scarborough Shoal, a contested maritime feature located in the West Philippine Sea – Manila’s name for part of the disputed South China Sea within its exclusive economic zone.

Jonathan Malaya, assistant director general of the National Security Council, told reporters that Philippine authorities were collecting evidence to file a case against China for destroying coral reefs around the shoal and its other illegal actions, including Chinese fishermen harvesting endangered giant clams.

Tayao said the outcome of such a case would likely favour Manila as indicated by legal precedents involving both countries over the South China Sea row.

“We won the arbitration case before so we should have a good chance. Consider as well that we have international public opinion on our side, so that political factor is likely to be an advantage as well,” he said.

The Philippines, China, Malaysia, Brunei and Vietnam have competing claims in the South China Sea. In 2016, the Permanent Court of Arbitration at The Hague dismissed China’s claims to the South China Sea as delineated in Chinese maps. China rejected the ruling, insisting it had jurisdiction over the waterways as indicated by its so-called nine-dash line.

Tayao noted that the filing of another case against China has been discussed for some time after Manila’s repeated diplomatic protests against Beijing were consistently ignored.

While Malaya did not provide a timeline for filing, he mentioned that the Justice Department was assessing the case.

“We are alarmed and worried about the situation that’s happening there … They are the ones that are there right now. They are preventing us from going inside the lagoon,” Malaya said as he challenged China to open Scarborough Shoal to international scrutiny so that its environmental state could be assessed.

“We can ask third-party environmental groups or even the United Nations to do a fact-finding mission to determine the environmental situation in Bajo de Masinloc,” he added, referring to the shoal by its name in the Philippines.

Jose Antonio Custodio, a defence analyst and fellow at the Consortium of Indo-Pacific Researchers, said Manila’s strategy in handling West Philippine Sea issues could help internationalise the dispute and pressure China to change its ways.

“There will be tensions, though it’s doubtful that it will lead to open conflict. But expect continued Chinese build up and harassment of Philippine vessels and garrisons in the West Philippine Sea and terse diplomatic exchanges between the two [countries],” Custodio told This Week in Asia.

“They will engage in a massive disinformation campaign in the Philippines to weaken the resolve of Filipinos and scare them with China’s might. More importantly, they will bankroll pro-Chinese quislings in the Philippines to ensure that, in 2025 and 2028, pro-Beijing politicians will be elected by the Filipino people,” he added.

Last week, the Chinese coastguard issued an order, set to take effect on June 15, authorising its personnel to detain foreign nationals for up to 60 days if they were caught trespassing in what it considered Beijing’s territorial waters.

Philippine lawmakers and officials denounced the order, with some threatening to take legal action against Beijing should the Chinese coastguard carry out any detainment with Manila’s exclusive economic zone.

The leader of a Filipino fishermen’s group has even threatened to kidnap 10 Chinese nationals in the country for every Filipino that Beijing detains.

Leonardo Cuaresma, the leader of the fisherman’s association of New Masinloc, a town facing the West Philippine Sea, issued the warning after the Chinese coastguard’s announcement.

“We are not afraid of that new policy because, in the first place, they can’t do it in our traditional fishing grounds within our territory. It’s within our exclusive economic zone,” Cuaresma said.

“If they are going to arrest and detain our Filipino fishermen … for every Filipino fisherman, I want to relay to them that we will abduct, detain or hold 10 Chinese nationals,” he stressed.

“We are not doing illegal things. We are fishing peacefully and in clean ways. We will fight for our rights until death. If they do it against us, we know that there are a lot of Chinese in our country. We will take up revenge if that’s what they want.”

Analysts agree that China has no legal standing to carry out its threats of detainment.

Jennifer Parker, an expert associate at the National Security College at the Australian National University, told This Week in Asia it would be illegal for Beijing to apply such a policy outside its territorial waters.

“Whilst China frequently undertakes actions against the UN Convention on the Law of the Sea, the capture of citizens from the countries with overlapping exclusive economic zones with China’s nine-dash line would be a significant escalation,” Parker said.

“Although I don’t see China using this law in the short term against Philippine fishermen because of the scale of escalation it would involve, it does mean that the Philippines will need to make an even more concerted effort to have a presence in the vicinity of the features contested by China.”

Ray Powell, a maritime security analyst at the Gordian Knot Center for National Security Innovation at Stanford University, said the announcement of the Chinese coastguard’s detainment order was a significant escalation by Beijing.

“It is important for affected countries and the larger international community to make clear that any such detention would be treated as illegal and an outrage against the international order,” Powell said.