Article 8 of the Law on National Borders 2003 stipulates that: “Historical waters are Vietnam’s waters which due to their special geographical conditions, are of importance to the country’s economy, defence and security; or the waters which are jointly managed, exploited and used by Vietnam and other countries under special regulation in the form of international treaties signed by the Socialist Republic of Vietnam and the concerning parties”.

Because there hasn’t been a demarcation agreement on the sea border between Vietnam and Cambodia, on July 7, 1982, the two countries signed an Agreement on "Historical waters of Vietnam and Cambodia", aiming to reach an agreement on the legal sovereignty of the islands, the scope and powers of management, exploitation and use of resources in the historical waters of each country; at the same time, ending the long and complicated disputes over sovereignty of the sea and islands in the history of relations between the two countries in the Gulf of Thailand (southwest of Vietnam). The agreement defines the common waters of the two countries as the sea lying between the coast of Kien Giang Province, Phu Quoc Island and Tho Chu Islands of Vietnam with the coast of Kampot Province and Poulowai Islands of Cambodia. Accordingly, the two countries have the right to apply legal regulations on historical waters like their internal waters.

Under this agreement, the two countries agreed to use the Brévie Line, a line adopted by Governor Brevie in 1939 as the dividing line of sovereignty over islands between the two countries. This is a sound and creative application of international laws as developing the demarcation of administrative and police management boundaries to the dividing line of islands in the historical waters of the two countries. Under the Agreement, patrol and control in this historical water will be carried out by the two sides; fishing of local people in this water still follows the traditional practices. The exploitation of natural resources, such as: oil and gas, minerals, burnt ice, etc., in the historical water will be decided by the two countries; without an agreement, neither party can unilaterally proceed. The agreement will be negotiated at an appropriate time on the basis of equality, friendship, and respective for each other's independence, sovereignty, territorial integrity, and legitimate interests to plan the maritime boundary between the two countries in the historical water. The agreement is of great political and legal significance in the history of relations between the two countries. In particular, the issue of sovereignty over the islands is handled in a rational manner, which is a legal basis for the two countries to manage, protect, exploit and use resources in the historical water.

Adhering to the Agreement, in recent years, the State, the Army, directly the Navy, have signed the Regulation on joint patrol and the establishment of a hotline with the Royal Cambodian Navy. At the same time, many measures have been taken to improve the efficiency of coordination between the two forces, in order to solve promptly and effectively handle situations arising in the historical water, contributing to maintaining security and safety in the Southwest seas of the country; prevent, repel the risk of conflict, create a peaceful and stable environment for the two countries to realize the goal of developing the marine economy and consolidating the cooperation and friendship for mutual development.

Nguyen Duc Phu