Since this stipulation exempts from obligatory arbitration such differences between the contracting parties as concern the interests of third parties, the question requires an answer whether in the controversial interpretation of the Hay-Pauncefote Treaty other States than Great Britain and the United States are interested. The term _interest_ is, however, a very wide one and so vague that it is very difficult to decide this question. Does "interest" mean "rights"? Or does it mean "advantages"? If it means "advantages," there is no doubt that in the Panama Canal conflict the interests of third parties are concerned, for the free use of the Canal by their vessels on terms of entire equality is secured to them by the Hay-Pauncefote Treaty. On the other hand, if "interests" means "rights," it can hardly be said that the interests of third parties are concerned in the dispute, for the Hay-Pauncefote Treaty is one to which only Great Britain and the United States are contracting parties, and according to the principle _pacta tertiis nec nocent nec prosunt_ no rights can accrue to third parties from a treaty. Great Britain has the right to demand from the United States, which owns and controls the Canal, that she shall keep the Canal open for the use of the vessels of all nations on terms of entire equality, but other States have no right to make the same claim. The case will be different when the Canal has been opened, and has been in use for such length of time as to call into existence--under the influence and working of the Hay-Pauncefote Treaty--a customary rule of International Law according to which the Canal is permanently neutralised and open to vessels of all nations, or when all maritime States, through formal accession to the Hay-Pauncefote Treaty, have entered into it with all rights and duties of the two contracting parties. So long as neither of these events has taken place Great Britain and the United States can at any moment, without the consent of third States, abrogate the Hay-Pauncefote Treaty and do away with the stipulation that the Canal shall be open to vessels of all nations on terms of entire equality. In this connection it is of interest to draw attention to the fact that, in compliance with Article XIX of the Hay-Varilla Treaty of November 18, 1903, Section 5 of the Panama Canal Act entirely exempts vessels of the Republic of Panama from payment of the Panama Canal tolls. It would seem that this exemption in favour of the vessels of the Republic of Panama violates Article III, No. 1, of the Hay-Pauncefote Treaty, although it is in conformity with Article XIX of the Hay-Varilla Treaty which stipulates that:-- "The Government of the Republic of Panama shall have the right to transport over the Canal its vessels and its troops and munitions of war in such vessels at all times without paying charges of any kind."