1962: The International Court of Justice rules that the Temple of Preah Vihear belongs to Cambodia

On 15 June 1962, the International Court of Justice (ICJ) delivered a landmark decision in the dispute between the Kingdom of Cambodia and the Kingdom of Thailand concerning the territorial sovereignty of the Temple of Preah Vihear. This judgment, the result of a thorough analysis of historical, geographical and legal factors, marks a major milestone in bilateral relations and underscores the importance of international law in the peaceful resolution of border disputes.

Background and issues at stake

The Temple of Preah Vihear is an ancient sanctuary located at the top of a promontory in the Dangrek mountain range, on the border between Thailand to the north and Cambodia to the south. This site, which is of major archaeological and cultural value, has been the subject of conflicting territorial claims between the two States, giving rise to a long-standing dispute.

 The central question before the ICJ was to determine which country the Temple belonged to, with reference to the borders defined by several Franco-Siamese treaties from the early 20th century. Cambodia argued that, in accordance with international agreements and the map produced by the Joint Boundary Commission, the Temple was located on its territory.

Thailand, on the other hand, claimed that the border line followed the edge of the escarpment, thus placing the Temple on its territory. The dispute also included the question of the withdrawal of Thai military forces stationed on the site since 1954.

The legal basis: Treaties and delimitation commissions

At the heart of the dispute is the Franco-Siamese Treaty of 13 February 1904, which established the border between France (protector of Cambodia) and Siam (now Thailand). This treaty designated the ridge line, or ‘watershed line’, as the natural border to be followed in the Dangrek region.

The precise demarcation was entrusted to a Franco-Siamese Joint Commission set up by the treaty, which was responsible for drawing the border on the ground. This commission carried out detailed topographical work in the region between 1905 and 1907, including a direct inspection of the Temple. It produced official maps, including the famous ‘Annex 1’, showing the Temple of Preah Vihear in Cambodian territory, despite a slight deviation from the actual watershed claimed by Thailand.

The crucial role of the Annex 1 map

The map known as Annex 1, drawn up under French supervision and officially communicated to Siam in 1908, was a central element of Cambodia's appeal. It showed the border line delimited by the Commission, placing the Temple within the Kingdom of Cambodia. Thailand, however, contested the validity of this map, arguing that it had never been formally adopted by the Joint Commission and that it contained a fundamental error in that it did not follow the true watershed.

The Court declared that even though the map had not been formally approved by the Commission in its entirety, it had nevertheless been tacitly accepted by Thailand, in particular because of its wide dissemination, the absence of any official challenge for more than fifty years, and its implicit acceptance by the conduct of the Thai authorities themselves. The Court thus emphasises the legal principle that silence in response to an official document published engages responsibility and amounts to tacit consent.

Analysis and decision of the Court

In its analysis, the Court highlights several major facts:

• Thailand has long used the disputed map for official purposes, despite its stated opposition to the line at the Temple.

• The Thai government never formally rejected the map or requested a review of the border for decades, including during diplomatic negotiations in 1925, 1937 and after the Second World War.

• An official visit to the temple in 1930 by Prince Damrong, welcomed by the French authorities on behalf of Cambodia, did not elicit any protest from Thailand, thus constituting implicit recognition of Cambodian sovereignty.

• Attempts at Cambodian administrative presence have been hampered by Thai military occupation since 1954, prompting Cambodia's initial complaint to the ICJ.

In view of these factors, the Court concluded that Thailand had tacitly accepted the line indicated by the Commission and that the Temple therefore fell within Cambodian sovereignty, in accordance with the official map.

Legal and diplomatic consequences

The judgment expressly orders Thailand:

• To withdraw its armed forces from the Temple area and return it to Cambodia.

• To return, if applicable, any cultural objects that may have been removed from the site since 1954.

Although delivered by a majority (nine judges in favour of sovereignty and three against), it marks a fundamental victory for Cambodia, based on respect for international law, in particular treaties, good faith and the implicit acts of States.

A symbolic judgement on the primacy of international law

This case perfectly illustrates the importance of historical agreements and the continuity of their application. The Court reiterates that the essential purpose of borders is stability and predictability, which cannot be called into question indefinitely for technical reasons or because of changing interpretations.

The judgment also emphasises that, in international law, tacit acceptance through conduct and silence often carries the same weight as formal agreements. This historic decision laid the foundations for peace between Cambodia and Thailand on this sensitive issue, giving priority to procedural justice over territorial disputes.

Conclusion

By ruling in favour of Cambodia and recognising the binding nature of the line established by the Joint Commission, the International Court of Justice not only delivered justice in a symbolic territorial dispute, but also reinforced the primacy of international law in the peaceful resolution of disputes.

The Temple of Preah Vihear, a cultural and religious treasure, has thus regained its official status as part of Cambodia, and this judgment remains a major reference in border law.

Summary based on the full judgment of the International Court of Justice, 15 June 1962