Effect of Changes in Government upon Treaties.
§ 521. As treaties are binding upon the contracting States, changes in the government or even in the form of government of one of the parties can as a rule have no influence whatever upon the binding force of treaties. Thus, for instance, a treaty of alliance concluded by a State with constitutional government remains valid, although the Ministry may change. And no head of a State can shirk the obligations of a treaty concluded by his State under the government of his predecessor. Even when a monarchy turns into a republic, or vice versa, treaty obligations regularly remain the same. For all such changes and alterations, important as they may be, do not alter the person of the State which concluded the treaty. If, however, a treaty stipulation essentially presupposes a certain form of government, then a change from such form makes such stipulation void, because its execution has become impossible.[887]
[887] See below, § [542]. Not to be confounded with the effect of changes in government is the effect of a change in international status upon treaties, as, for instance, if a hitherto full-sovereign State becomes half- or part-Sovereign, or vice versa, or if a State merges entirely into another, and the like. This is a case of succession of States which has been discussed above, §§ [82]-84; see also below, § [548].
Effect of Treaties upon third States.
§ 522. According to the principle pacta tertiis nec nocent nec prosunt, a treaty concerns the contracting States only; neither rights nor duties, as a rule, arise under a treaty for third States which are not parties to the treaty. But sometimes treaties have indeed an effect upon third States. Such an effect is always produced when a treaty touches previous treaty rights of third States. Thus, for instance, a commercial treaty conceding more favourable conditions than hitherto have been conceded by the parties thereto has an effect upon all such third States as have previously concluded commercial treaties containing the so-called most-favoured-nation clause[888] with one of the contracting parties.
[888] See below, § [580], but note the American interpretation of this clause.
The question arises whether in exceptional cases third States can acquire rights under such treaties as were specially concluded for the purpose of creating such rights not only for the contracting parties but also for third States. Thus, the Hay-Pauncefote Treaty between Great Britain and the United States of 1901, and the Hay-Varilla Treaty between the United States and Panama of 1903, stipulate that the Panama Canal to be built shall be open to vessels of commerce and of war of all nations, although Great Britain, the United States, and Panama only are parties.[889] Thus, further, article 5 of the Boundary Treaty of Buenos Ayres of September 15, 1881, stipulates that the Straits of Magellan shall be open to vessels of all nations, although Argentina and Chili only are parties. Again, the Treaty of Paris, signed on March 30, 1856, and annexed to the Peace Treaty of Paris of 1856, stipulates that Russia shall not fortify the Aland[890] Islands; although this stipulation was made in the interest of Sweden, only Great Britain, France, and Russia are parties. I believe that the question must be answered in the negative, and nothing prevents the contracting parties from altering such a treaty without the consent of third States, provided the latter have not in the meantime acquired such rights through the unanimous tacit consent of all concerned.
[890] See above, [§ 205, p. 277, note 2].
It must be emphasised that a treaty between two States can never invalidate a stipulation previously created by a treaty between one of the contracting parties and a third State, unless the latter expressly consents. If, for instance, two States have entered into an alliance and one of them afterwards concludes a treaty with a third State, according to which all conflicts without exception shall be settled by arbitration, the previous treaty of alliance remains valid even in the case of war breaking out between the third State and the other party to the alliance.[891] Therefore, when in 1911 Great Britain contemplated entering, with the United States of America, into a treaty of general arbitration according to which all differences should be decided by arbitration, she notified Japan of her intention, on account of the existing treaty of alliance, and Japan consented to substitute for the old treaty a new treaty of alliance,[892] article 4 of which stipulates that the alliance shall never concern a war with a third Power with whom one of the allies may have concluded a treaty of general arbitration.