Why did Cambodia choose June 15 to file a border dispute with the ICJ?
Cambodia’s decision to submit a letter to the International Court of Justice (ICJ) regarding border disputes involving the Emerald Triangle (Mom Bei), Ta Moan Thom, Ta Moan Tauch, and Ta Krabei temples on Sunday (June 15) was no coincidence.
According to a report by Thansettakij, the date marks the 63rd anniversary of Cambodia’s historic victory in the Preah Vihear case, when the ICJ ruled in its favour.
On June 15, 1962, the ICJ delivered its judgment on the Preah Vihear Temple, located near Kantharalak district in Thailand’s Sisaket province, in a decisive 9-3 ruling against Thailand.
The case, brought by Cambodia in 1959, asked the court to determine ownership of the temple and order Thailand to withdraw its troops from the site. It became a landmark legal and diplomatic victory for Cambodia.
This ruling not only returned the temple to Cambodian control but also entitled Phnom Penh to demand the return of Khmer artefacts removed from the site, as well as requiring Thailand to withdraw its military and police from the temple and surrounding areas.
The decision to revive the border dispute on June 15 — a date loaded with symbolic meaning — reflects a calculated diplomatic strategy. The public remarks by Senate President Hun Sen and Prime Minister Hun Manet at this time further underline Cambodia’s multi-layered signalling.
Lessons from the past still echo today
Although Thailand strongly disagreed with the 1962 ruling, as a member of the United Nations (UN), it was obliged to comply under Article 94 of the UN Charter, which states that each member undertakes to abide by the decisions of the ICJ in any case to which it is a party.
Three dissenting ICJ judges argued that the temple rightfully belonged to Thailand, citing technical and legal grounds. However, their opinions held no legal weight, serving only academic purposes.
Judge Lucio Moreno Quintana, for instance, believed that the boundary demarcation on the map used by Cambodia was flawed and not explicitly accepted by Thailand.
Judge Wellington Koo questioned the principle of acquiescence, arguing it could not be applied in this case. Judge Sir Percy Spender emphasised that the boundary should follow the watershed line under the 1904 Franco-Siamese Convention.
Nonetheless, these dissenting views could not overturn the ruling — and Cambodia has since continued to draw on that victory as a reference point in ongoing diplomatic efforts.
Legal limitations, strategic openings
One key aspect of the 1962 ICJ ruling is that it did not adjudicate the entire boundary between Thailand and Cambodia. Specifically, the court did not rule that the border must align with the 1:200,000-scale map Cambodia used as evidence.
This limitation could provide Thailand with an opportunity. If current disputes can be separated from the Preah Vihear case, a new negotiation framework might be possible — one less burdened by historical precedent.
Looking ahead
Cambodia’s deliberate choice of June 15 highlights how history continues to shape modern diplomacy. For Thailand, learning from past outcomes and preparing both diplomatically and legally will be vital in addressing this new challenge.
June 15 is more than just a historical anniversary — it has become a political tool. Cambodia is using it to frame the current dialogue in its favour, effectively challenging Thailand to break free from the shadows of the past and seek innovative paths forward.
