The Court cannot accept these contentions either on the facts or the law. If the Siamese authorities did show these maps only to minor officials, they clearly acted at their own risk, and the claim of Thailand could not, on the international plane, derive any assistance from that fact. But the history of the matter, as set out above, shows clearly that the maps were seen by such persons as Prince Devawongse, the Foreign Minister, Prince Damrong, the Minister of the Interior, the Siamese members of the First Mixed Commission, the Siamese members of the Commission of Transcription; and it must also be assumed that the Annex 1 map was seen by the Governor of Khukhan province, the Siamese province adjoining the Preah Vihear region on the northern side, who must have been amongst those for whom extra copies were requested by Prince Damrong. None of these persons was a minor official. All or most had local knowledge. Some must have had knowledge of the Dangrek region. It is clear from the documentation in the case that Prince Damrong took a keen personal interest in the work of delimitation, and had a profound knowledge of archaeological monuments. It is not conceivable that the Governor of Khukhan province, of which Preah Vihear formed part up to the 1904 settlement, was ignorant of its existence.

In any case this particular contention of Thailand's is decisively disproved by a document deposited by Thailand herself, according to which the Temple was in 1899 "re-discovered" by the Siamese Prince Sanphasit, accompanied by some fifteen to twenty officials and local dignitaries, including, it seems, the then Governor and Deputy-Governor of Khukhan. It thus appears that only nine years previous to the receipt of the Annex 1 map by the Siamese authorities, a considerable number of persons having high official standing in Siam knew of Preah Vihear.

The Court moreover considers that there is no legal foundation for the consequence it is attempted to deduce from the fact that no one in Thailand at that time may have known of the importance of the Temple or have been troubling about it. Frontier rectifications cannot in law be claimed on the ground that a frontier area has turned out to have an importance not known or suspected when the frontier was established.

It follows from the preceding findings that the Siamese authorities in due course received the Annex 1 rnap and that they accepted it. Now, however, it is contended on behalf of Thailand, so far as the disputed area of Preah Vihear is concerned, that an error was committed, an error of which the Siamese authorities were unaware at the time when they accepted the map.

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 if the circumstances were such as to put that party on notice of a possible error. The Court considers that the character and qualifications of the persons who saw the Annex 1 rnap on the Siamese side would alone make it difficult for Thailand to plead error in law. These persons included the members of the very Commission of Delimitation within whose competence this sector of the frontier had lain. But even apart from this, the Court thinks that there were other circumstances relating to the Annex 1 map which make the plea of error difficult to receive.

An inspection indicates that the map itself drew such pointed attention to the Preah Vihear region that no interested person, nor anyone charged with the duty of scrutinizing it, could have failed to see what the map was purporting to do in respect of that region. If, as Thailand has argued, the geographical configuration of the place is such as to make it obvious to anyone who has been there that the watershed must lie along the line of the escarpment (a fact which, if true, must have been no less evident in 1908), then the map made it quite plain that the Annex 1 line did not follow the escarpment in this region since it was plainly drawn appreciably to the north of the whole Preah Vihear promontory. Nobody looking at the map could be under any misapprehension about that.

Next, the map marked Preah Vihear itself quite clearly as lying on the Cambodian side of the line, using for the Temple a symbol which seems to indicate a rough plan of the building and its stairways.

It would thus seem that, to anyone who considered that the line of the watershed at Preah Vihear ought to follow the line of the escarpment, or whose duty it was to scrutinize the map, there was everything in the Annex 1 map to put him upon enquiry. Furthermore, as has already been pointed out, the Siamese Government knew or must be presumed to have known, through the Siamese members of the Mixed Commission, that the Annex 1 map had never been formally adopted by the Commission. The Siamese authorities knew it was the work of French topographical officers to whom they had themselves entrusted the work of producing the maps. They accepted it without any independent investigation, and cannot therefore now plead any error vitiating the reality of their consent. The Court concludes therefore that the plea of error has not been made out.

Part 12