Prime Minister Hun Manet’s official visit to Japan from May 28 to 31 marks a pivotal moment for Cambodia to reaffirm its commitment to maritime sovereignty and the international rules-based order by formally endorsing the United Nations Convention on the Law of the Sea (UNCLOS).

Often referred to as the "constitution of the ocean," UNCLOS provides a legal framework not only for governing maritime rights and resources but also for settling disputes through peaceful, lawful means. Ratifying the treaty would not only strengthen Cambodia’s maritime claims but also signal its broader commitment to international legal norms and peaceful cooperation in a region where competing interests at sea continue to rise.

Endorsing UNCLOS should be seen as part of Cambodia’s long-standing and strategic reliance on international law as a tool for asserting its sovereignty, maintaining regional stability, and safeguarding national development. International law has long served as the foundation of the global rules-based system—guiding stable interstate relations, fostering cooperation, and promoting peaceful dispute resolution.

For smaller states like Cambodia, this legal framework is not merely aspirational but essential. It offers a structured way to navigate a complex international landscape often shaped by the competing agendas of larger powers.

The Strength and Relevance of International Law

Cambodia’s experience with international law underscores its critical value in navigating complex sovereignty disputes—whether on land or at sea. The recent escalation of tensions with Thailand over the Ta Moan Thom and Preah Vihear temple complexes has once again exposed the volatility of unresolved border issues.

On May 28, a brief but deadly exchange of gunfire between Cambodian and Thai troops near Preah Vihear tragically claimed the life of a Cambodian warrant officer, starkly illustrating how historical grievances, if left legally unsettled or politically mismanaged, can spiral into violence.

This latest incident reinforces the urgent need for legally binding frameworks—like those enshrined in the United Nations Convention on the Law of the Sea — to preempt and peacefully resolve disputes. Just as the International Court of Justice (ICJ) helped clarify Cambodia’s sovereign rights over Preah Vihear, UNCLOS provides a similarly robust legal basis for addressing maritime boundaries and overlapping claims. Ratifying UNCLOS would further equip Cambodia to handle future disputes with legal precision, reinforcing the principle that the rule of law—not force—should guide regional relations.

When Cambodia successfully registered the 1,000-year-old temple as a UNESCO World Heritage Site in 2008, tensions flared again with Thailand, prompting Cambodia to seek a reinterpretation of the ICJ decision. In 2013, the Court confirmed that Cambodia also holds sovereignty over the surrounding land. While the ruling offered a clear legal conclusion, the two countries have yet to fully implement it—raising the risk of further violence if law is not upheld.

Cambodia’s successful appeal to international legal institutions during the Preah Vihear dispute showcased the power of global law to protect national interests without resorting to force. By turning to the International Court of Justice, Cambodia was able to affirm its sovereign rights and de-escalate a potentially dangerous conflict through peaceful, legal means.

This experience offers a compelling precedent—demonstrating that legal frameworks can be more effective than military responses in settling disputes. The same logic should now apply to Cambodia’s maritime domain: by acceding to UNCLOS, Phnom Penh would reinforce its commitment to lawful dispute resolution and equip itself with the legal tools needed to safeguard its maritime sovereignty in a similarly principled and peaceful manner.

As a member of ASEAN, Cambodia has consistently promoted international law and multilateral cooperation. The Kingdom has supported foundational instruments such as the UN and ASEAN Charters, the Treaty of Amity and Cooperation (TAC), international humanitarian law, and key human rights treaties. Phnom Penh has repeatedly affirmed its dedication to global norms that emphasize diplomacy, dialogue, and legal resolution over aggression and unilateralism.

Ratifying UNCLOS would be a strategic and timely move for Cambodia—one that aligns with its longstanding commitment to international law and multilateral cooperation. Acceding to this landmark treaty would provide legal protections for Cambodia’s maritime sovereignty along its nearly 450 kilometers of coastline, including sovereign rights over valuable marine resources within its territorial seas and exclusive economic zone. These resources are vital for Cambodia’s national development, offering opportunities for sustainable economic growth through fisheries, offshore energy, and marine biodiversity.

Beyond securing its maritime assets, UNCLOS ratification would strengthen Cambodia’s legal footing in regional maritime affairs, particularly in resolving potential overlapping claims with neighboring countries. By embracing a rules-based approach to maritime governance, Cambodia would reinforce peaceful dispute settlement mechanisms and foster deeper cooperation over shared maritime resources in the region.

More than just a legal formality, this step would send a powerful signal to the region—and the international community—that Cambodia sees international law not as a privilege reserved for powerful states, but as an essential safeguard for all nations, particularly smaller ones.

This perspective has been echoed by regional and local experts, including through recent conferences hosted by the Cambodian Center for Regional Studies, which have emphasized the strategic value of international legal instruments like UNCLOS.

Ratifying UNCLOS will Elevate Cambodia’s Credibility

Drawing on such expert consensus, Cambodia is well-positioned to join the ranks of responsible, forward-looking states that uphold and benefit from the international legal order. Ratifying UNCLOS would not only elevate Cambodia’s credibility on the global stage but also solidify its role as a principled advocate for peace, cooperation, and lawful conduct at sea.

For instance, during a public lecture on “Evolving UNCLOS Towards Maritime Cooperation” on March 18, Judge Hidehisa Horinouchi, Member of the International Tribunal for the Law of the Sea, stressed the importance of Cambodia joining its ASEAN counterparts in fully adopting UNCLOS to secure its maritime rights and cooperation mechanisms.

He stated that Cambodia “becoming a member [of UNCLOS] would offer clearer, definitive rights and obligations regarding Cambodia’s EEZ”.

Another attribution was made during a public lecture on “Roles of International Law in Promoting Peaceful Dispute Settlement in the Indo-Pacific” on January 29 where a Japanese expert, Professor Shotaro Hamamoto of Kyoto University pinpointed that, “If you participate as a member, as a state party to UNCLOS, then you can make use of a wide variety of opportunities, such as a conference of parties, which examines the implementation of the convention, and if you really wish to settle a dispute through legal, judicial means”.

Similarly, at the same event, Cambodia’s former industry, mines and energy minister Pou Sothirak gave another resounding ascription of UNCLOS.

“If we ratify UNCLOS, we can also protect what is in the sea that belongs to Cambodia. We have a very long coastline, and according to international law, the 200 nautical miles extend from the land and include maritime resources – Cambodia can have rightful ownership to these maritime bounties, including fisheries and what’s underneath, which could be oil and gas,” he said. 

During the official working visit to Japan by Prime Minister Hun Manet, Cambodia would do Tokyo justice by announcing its decision to ratify UNCLOS. Japan is keen to see Cambodia as a new member of UNCLOS. This way, Cambodia and Japan can look forward to galvanizing their strategic trust and friendship in support of international laws and the rules-based international order.

At the time of changes and turbulences culminating from sovereignty disputes over land and maritime boundaries between neighboring countries, Cambodia’s best option is to rely on international laws to warrant its sovereign rights over territorial land and sea.

If and when Cambodia ratifies UNCLOS, the country can count on this convention to protect its rights and safeguard its legal maritime sovereignty against bigger neighbors from the East and West. UNCLOS has what it takes to advance peaceful settlements of disputes at sea, be it overlapping territorial and maritime claims or the sea resources. Now is the right time for Cambodia to embrace UNCLOS firmly.

Him Raksmey is the Executive Director of the Cambodian Center for Regional Studies