Five and a half years on from the international arbitral tribunal’s rejection of China’s expansive South China Sea claims in July 2016, the international maritime order in East Asia clearly is in trouble. China is continuing to consolidate its control over the Paracel Islands and most of the Spratleys group and is increasing its encroachments on the recognised exclusive economic zones of most of the South China Sea’s littoral states with relative impunity. The Philippines and Vietnam in particular have suffered numerous Chinese incursions, and Indonesia’s Natuna Islands and more recently Malaysia’s EEZ have been targeted in China’s bid to control the southern waters of the first island chain.

The region’s maritime order under the United Nations Convention on the Law of the Sea is central to the rules-based order that Australia, India, Japan, the US and other likeminded states hold to be central to regional security and prosperity. Yet China’s grey-zone tactics are continuing apace, weakening the authority and relevance of UNCLOS in the absence of a coordinated and unified regional stance supporting its rules and authority both in principle and in practice.

The wider regional implications of China continuing to unilaterally impose its own maritime laws on other states, denying them fishing and other maritime rights, provide compelling reasons for the Quad states, and others, to work harder to ensure that the rights and entitlements of all South China Sea littoral states under UNCLOS are protected. The threats include not only the further erosion of the rules-based order’s authority and legitimacy, perhaps to an irreparable degree, but also a major increase in Beijing’s political and economic leverage over the many Southeast Asian states that continue to depend on the fishing, energy and other sovereign rights China seeks to control.

Allowing Beijing to further expand its already significant presence and influence in the South China Sea would make it much more difficult for Australia, Japan and the US to build regional diplomatic support against China’s actions in the South China Sea and elsewhere, making great-power military conflict in the region more likely.

ASEAN’s role in the disputes remains hamstrung by internal divisions over its responsibility as a regional institution for protecting individual state maritime rights, despite its various statements affirming UNCLOS ^[1] as the basis for resolving maritime entitlement disputes. Many in ASEAN are fearful of the consequences of being forced to choose between the US and China, of ASEAN becoming marginalised by great-power politics in its own backyard, and of the region becoming more militarised and conflict prone.

The lack of a unified ASEAN stance and response on China’s claims is also explained by fence-sitting among member states that are not directly affected by the South China Sea disputes or whose political and business elites prioritise the benefits ^[2] of not antagonising Beijing. The fact that rival maritime claimants in ASEAN hold conflicting interpretations ^[3] of UNCLOS’s provisions has been an additional obstacle to developing a common ASEAN position.

But signs of greater willingness to cooperate ^[4] on maritime law enforcement and other maritime issues, encouraged by Beijing’s aggressive behaviour, are beginning to appear ^[5] among the littoral ASEAN states. An agreement between Indonesia and the Philippines on their overlapping EEZs in the Celebes Sea was ratified by both governments in 2014. Vietnam and Malaysia are planning to sign a memorandum of understanding ^[6] on maritime security cooperation addressing several problem areas, including illegal Vietnamese fishing in Malaysian waters. Vietnam and Indonesia ^[7], meanwhile, are continuing negotiations to establish provisional boundaries in overlapping areas of their claimed EEZs in the North Natuna Sea; in December last year the two nations signed a memorandum ^[8] pledging improved cooperation on maritime security and safety.

These bilateral agreements should be read as both an assertion of the parties’ maritime rights and a clear rejection of China’s illegal ‘nine-dash line’ claims.

Beijing’s deployment of militia vessels for maritime fishing exposes them to suspicion of illegal fishing and thus also to legitimate maritime law enforcement action under UNCLOS. The longstanding problem of Illegal, unreported and unregulated fishing in the South China Sea therefore may present an important opportunity ^[9] for the South China Sea states most at threat from China’s illegal maritime claims—the Philippines, Vietnam, Malaysia and Indonesia—to collectively develop, with greater capacity-building and regulatory support from the Quad states, a UNCLOS based, non-military means of pushing back against China’s claims and grey-zone tactics.

Doing so will ensure that regional, rather than external, actors take the lead in upholding and affirming maritime rights. It will also provide a broad and unambiguous affirmation of UNCLOS’s authority and relevance and place the onus for any military escalation on China by imposing grey-zone dilemmas on China’s leadership, especially in terms of its own conflict threshold calculations.

Aside from the geostrategic threat that a Chinese takeover of the South China Sea poses, the alternative to cooperative EEZ regulation and better maritime law enforcement is a Chinese-controlled South China Sea. That would extinguish the resource and freedom-of-navigation rights of all other states and make any plans for cooperative or multilateral management (such as through a regional fisheries management organisation) of those resources and rights redundant. The risk of a catastrophic collapse of the region’s biggest fisheries resource due to Chinese mismanagement ^[10], intensifying competition and conflict, or both, would significantly increase. Such an outcome would very likely mean more illegal fishing in Southeast Asia’s already depleted waters, and in the EEZs of other states, including Australia and Japan.

By collectively supporting the Philippines, Malaysia, Vietnam and Indonesia in their efforts to more effectively regulate and police fishing and other maritime activities, the Quad states can indirectly push back on China’s grey-zone encroachments while also helping the coastal states to better manage a longstanding threat to the region’s socioeconomic security and future prosperity.