(2) If an external affair of a State is at the same time by right an affair of another State, the latter has a right to intervene in case the former deals with that affair unilaterally. The events of 1878 provide an illustrative example. Russia had concluded the preliminary Peace of San Stefano with defeated Turkey; Great Britain protested because the conditions of this peace were inconsistent with the Treaty of Paris of 1856 and the Convention of London of 1871, and Russia agreed to the meeting of the Congress of Berlin for the purpose of arranging matters. Had Russia persisted in carrying out the preliminary peace, Great Britain as well as other signatory Powers of the Treaty of Paris and the Convention of London doubtless possessed a right of intervention.
(3) If a State which is restricted by an international treaty in its external independence or its territorial or personal supremacy does not comply with the restrictions concerned, the other party or parties have a right to intervene. Thus the United States of America, in 1906, exercised intervention in Cuba in conformity with article 3 of the Treaty of Havana[215] of 1903, which stipulates: "The Government of Cuba consents that the United States may exercise the right to intervene for the preservation of Cuban independence, the maintenance of a Government adequate for the protection of life, property, and individual liberty...." And likewise the United States of America, in 1904, exercised intervention in Panama in conformity with article 7 of the Treaty of Washington[216] in 1903, which stipulates: "The same right and authority are granted to the United States for the maintenance of public order in the cities of Panama and Colon and the territories and harbours adjacent thereto in case the Republic of Panama should not be, in the judgment of the United States, able to maintain such order."
[215] See Martens, N.R.G. 2nd Ser. XXXII. (1905), p. 79.—Even if no special right of intervention is stipulated, it nevertheless exists in such cases. Thus—see below, § [574]—those Powers which have guaranteed the integrity of Norway under the condition that she does not cede any part of her territory to any foreign Power would have a right to intervene in case such a cession were contemplated, although the treaty concerned does not stipulate this.
[216] See Martens, N.R.G. 2nd Ser. XXXI. (1905), p. 599.
(4) If a State in time of peace or war violates such rules of the Law of Nations as are universally recognised by custom or are laid down in law-making treaties, other States have a right to intervene and to make the delinquent submit to the rules concerned. If, for instance, a State undertook to extend its jurisdiction over the merchantmen of another State on the high seas, not only would this be an affair between the two States concerned, but all other States would have a right to intervene because the freedom of the open sea is a universally recognised principle. Or if a State which is a party to the Hague Regulations concerning Land Warfare were to violate one of these Regulations, all the other signatory Powers would have a right to intervene.
(5) A State that has guaranteed by treaty the form of government of a State or the reign of a certain dynasty over the same has a right[217] to intervene in case of change of form of government or of dynasty, provided the respective treaty of guaranty was concluded between the respective States and not between their monarchs personally.
[217] But this is not generally recognised; see, for instance, Hall, § 93, who denies the existence of such a right. I do not see the reason why a State should not be able to undertake the obligation to retain a certain form of government or dynasty. That historical events can justify such State in considering itself no longer bound by such treaty according to the principle rebus sic stantibus (see below, § [539]) is another matter.
(6) The right of protection[218] over citizens abroad, which a State holds, may cause an intervention by right to which the other party is legally bound to submit. And it matters not whether protection of the life, security, honour, or property of a citizen abroad is concerned.
The so-called Drago[219] doctrine, which asserts the rule that intervention is not allowed for the purpose of making a State pay its public debts, is unfounded, and has not received general recognition, although Argentina and some other South American States tried to establish this rule at the second Hague Peace Conference of 1907. But this Conference adopted, on the initiative of the United States of America, a "Convention[220] respecting the Limitation of the Employment of Force for the Recovery of Contract Debts." According to article 1 of this Convention, the contracting Powers agree not to have recourse to armed force for the recovery of contract debts claimed from the Government of one country by the Government of another country as being due to its nationals. This undertaking is, however, not applicable when the debtor State refuses or neglects to reply to an offer of arbitration, or, after accepting the offer, renders the settlement of the compromis impossible, or, after the arbitration, fails to submit to the award.—It must be emphasised that the stipulations of this Convention concern the recovery of all contract debts, whether or no they arise from public loans.