New regulations from China now empower its coastguard to detain foreign nationals for trespassing in the contested South China Sea, a move that has been widely criticized by nearby nations.

China asserts sovereignty over most of the South China Sea, dismissing rival claims from Southeast Asian countries, including the Philippines, and disregarding a 2016 ruling by an arbitration tribunal in The Hague that invalidated its expansive claims.

The Chinese government continues to send coastguard and other vessels to patrol the waters it deems its own, militarizing several reefs into fortified artificial islands. In recent years, tensions have escalated due to confrontations between Chinese and Philippine ships in these contested waters.

Starting Saturday, China's coastguard has the authority to detain foreigners "suspected of violating border entry and exit management," as per the regulations made available online.

These new rules permit detention for up to 60 days in complicated cases, stating that "foreign ships illegally entering China's territorial and adjacent waters may be detained."

Philippine President Ferdinand Marcos Jr recently described the new regulations as a "very worrisome" escalation. On Saturday, the Philippines’ Department of Foreign Affairs announced it had made legal submissions to the United Nations in New York, affirming its “maritime entitlements” under UN maritime laws to an expanded continental shelf in parts of the South China Sea, which it terms the West Philippine Sea.

The Philippines has accused China's coastguard of “barbaric and inhumane acts” against its vessels, citing instances where Chinese coastguard ships deployed water cannons against Philippine boats in disputed waters, resulting in injuries to Filipino soldiers.

General Romeo Brawner, the Philippine military chief, informed the media that discussions were underway in Manila concerning measures to safeguard their fishermen.

Brawner urged Philippine fishermen to continue their normal activities within the country's Exclusive Economic Zone, advising them not to fear the newly imposed Chinese regulations.

The Group of Seven (G7), comprising major economies, criticized China's actions on Friday, labeling them “dangerous” incursions in the vital shipping route, where countries like Vietnam, Malaysia, and Brunei also hold overlapping territorial claims.

Annually, trillions of dollars in trade transit through the South China Sea, with vast unexploited oil and gas reserves expected beneath its seafloor. The region also serves as a significant fishing ground for increasing populations.

China defends its coastguard regulations, with a foreign ministry spokesperson stating the rules aim to “better uphold order at sea.” This sentiment was echoed by the Chinese defense minister's recent remarks about the limits of Beijing’s patience in the South China Sea.

China has shown displeasure over previous instances of U.S. and Western warships navigating through the South China Sea, actions intended to affirm international maritime freedom. Beijing sees these voyages as intrusions on its sovereignty, leading to several close encounters between Chinese and American military forces in these waters.