In these circumstances Cambodia, on attaining her independence in 1953, proposed, for her part, to send keepers or guards to the Temple, in the assertion or maintenance of her position. However, finding that Thai keepers were already there, the Cambodian keepers withdrew, and Cambodia sent a Note dated January 1954 to the Government of Thailand asking for information. This received a mere acknowledgment, but no explanation. Nor was there, even then, any formal affirmation of Thailand's claim. At the end of March 1954, the Government of Cambodia, drawing attention to the fact that no substantive reply to its previous Note had been received, notified the Government of Thailand that it now proposed to replace the previously withdrawn Cambodian keepers or guards by some Cambodian troops. In this Note Cambodia specifically referred to the justification of the Cambodian claim contained in the French Note of May 1949. This Cambodian Note also was not answered. However, the Cambodian troops were not in fact sent; and in June 1954, Cambodia addressed to Thailand a further Note stating that, as information had been received to the effect that Thai troops were already in occupation, the despatch of the Cambodian troops had been suspended in order not to aggravate the situation. The Note went on to ask that Thailand should either withdraw her troops or furnish Cambodia with her views on the matter. This Note equally received no reply. But the Thai "troops" (the Court understands that they are in fact a police force) remained. Again, therefore, it would seem that Thailand, while taking certain local action, was not prepared to deny the French and Cambodian claim at the diplomatic level.

No further diplomatic correspondence was produced to the Court ; but eventually, in 1958, a conference was held at Bangkok between Thailand and Cambodia, to discuss various territorial matters in dispute between the Parties, including that of Preah Vihear. The representative of Thailand having declined to discuss the legal aspects of the matter, the negotiations broke down and Cambodia instituted the present proceedings.

The Court will now state the conclusions it draws from the facts as above set out.

Even if there were any doubt as to Siam's acceptance of the map in 1908, and hence of the frontier indicated thereon, the Court would consider, in the light of the subsequent course of events, that Thailand is now precluded by her conduct from asserting that she did not accept it. She has, for fifty years, enjoyed such benefits as the Treaty of 1904 conferred on her, if only the benefit of a stable frontier. France, and through her Cambodia, relied on Thailand's acceptance of the map. Since neither side can plead error, it is immaterial whether or not this reliance was based on a belief that the map was correct. It is not now open to Thailand, while continuing to claim and enjoy the benefits of the settlement, to deny that she was ever a consenting party to it.

The Court however considers that Thailand in 1908-1909 did accept the Annex 1 map as representing the outcome of the work of delimitation, and hence recognized the line on that map as being the frontier line, the effect of which is to situate Preah Vihear in Cambodian territory. The Court considers further that, looked at as a whole, Thailand's subsequent conduct confirms and bears out her original acceptance, and that Thailand's acts on the ground do not suffice to negative this. Both Parties, by their conduct, recognized the line and thereby in effect agreed to regard it as being the frontier line.

The Court must now consider two further matters. Thailand contends that since 1908, and at any rate up to her own 1934-1935 survey, she believed that the map line and watershed line coincided, and therefore that if she accepted the map line, she did so only in that belief. It is evident that such a contention would be quite inconsistent with Thailand's equally strongly advanced contention that these acts in the concrete exercise of sovereignty evidenced her belief that she had sovereignty over the Temple area: for if Thailand was truly under a misapprehension about the Annex 1 line - if she really believed it indicated the correct watershed line - then she must have believed that, on the basis of the map and her acceptance of it, the Temple area lay rightfully in Cambodia. If she had such a belief - and such a belief is implicit in any plea that she had accepted the Annex 1 map only because she thought it was correct - then her acts on the ground would have to be regarded as deliberate violations of the sovereignty which (on the basis of the assumptions above stated) she must be presumed to have thought Cambodia to possess. The conclusion is that Thailand cannot allege that she was under any misapprehension in accepting the Annex 1 line, for this is wholly inconsistent with the reason she gives for her acts on the ground, namely that she believed herself to possess sovereignty in this area.

It may be added that even if Thailand's plea of misapprehension could, in principle, be accepted, it should have been advanced shortly after Thailand's own survey of the disputed region was carried out in 1934-1935. Since then Thailand could not have been under any misapprehension.

There is finally one further aspect of the case with which the Court feels it necessary to deal. The Court considers that the acceptance of the Annex 1 map by the Parties caused the map to enter the treaty settlement and to become an integral part of it. It cannot be said that this process involved a departure from, and even a violation of, the terms of the Treaty of 1904, wherever the map line diverged from the line of the watershed, for, as the Court sees the matter, the map (whether in all respects accurate by reference to the true watershed line or not) was accepted by the Parties in 1908 and thereafter as constituting the result of the interpretation given by the two Governments to the delimitation which the Treaty itself required. In other words, the Parties at that time adopted an interpretation of the treaty settlement which caused the map line, in so far as it may have departed from the line of the watershed, to prevail over the relevant clause of the treaty. Even if, however, the Court were called upon to deal with the matter now as one solely of ordinary treaty interpretation, it considers that the interpretation to be given would be the same, for the following reasons.

In general, when two countries establish a frontier between them, one of the primary objects is to achieve stability and finality. This is impossible if the line so established can, at any moment, and on the basis of a continuously available process, be called in question, and its rectification claimed, whenever any inaccuracy by reference to a clause in the parent treaty is discovered. Such a process could continue indefinitely, and finality would never be reached so long as possible errors still remained to be discovered. Such a frontier, so far from being stable, would be completely precarious. It must be asked why the Parties in this case provided for a delimitation, instead of relying on the Treaty clause indicating that the frontier line in this region would be the watershed. There are boundary treaties which do no more than refer to a watershed line, or to a crest line, and which make no provision for any delimitation in addition. The Parties in the present case must have had a reason for taking this further step. This could only have been because they regarded a watershed indication as insufficient by itself to achieve certainty and finality. It is precisely to achieve this that delimitations and map lines are resorted to.

Various factors support the view that the primary object of the Parties in the frontier settlements of 1904-1908 was to achieve certainty and finality. From the evidence furnished to the Court, and from the statements of the Parties themselves, it is clear that the whole question of Siam's very long frontiers with French Indo-China had, in the period prior to 1904, been a cause of uncertainty, trouble and friction, engendering what was described in one contemporary document placed before the Court as a state of "growing tension" in the relations between Siam and France. The Court thinks it legitimate to conclude that an important, not to say a paramount object of the settlements of the 1904-1908 period (which brought about a comprehensive regulation of all outstanding frontier questions between the two countries), was to put an end to this state of tension and to achieve frontier stability on a basis of certainty and finality.

Part 15