Case concerning the Temple of Preah Vihear Cambodia v Thailand Merits

In 1904, the boundary between Cambodia (protectorate of France) and Siam (Thailand) in Preah Vihear was determined by Treaty. The treaty stated that it had to follow the watershed line. The final stage of delimitation was the preparation of maps. Siamese government asked France to prepare the maps. In one of them Preah Vihear was on the Cambodia side. Thailand held that if she had accepted the map, she had done so because a mistaken belief that the frontier indicated corresponded with the watershed line.

It is an established rule of law that the plea of error cannot be allowed as an element vitiating consent if the party advancing it contributed by its own conduct to the error, or could have avoided it, or it the circumstances were such as to put that party on notice of a possible error. Maps were communicated to Siamese government (Thailand) since no reaction was made, they must be held to have acquiesced.