[Footnote 219: The Drago doctrine originates from Louis M. Drago, sometime Foreign Secretary of the Republic of Argentina. See Drago, "Cobro coercitivo de deudas publicas" (1906); Barclay, "Problems of International Practice, &c." (1907), pp. 115-122; Moulin, "La Doctrine de Drago" (1908); Higgins, "The Hague Peace Conferences, &c." (1909), pp. 184-197; Scott, "The Hague Peace Conferences" (1909), vol. I. pp. 415-422; Calvo in R.I. 2nd Ser. V. (1903), pp. 597-623; Drago in R.G. XIV. (1907), pp. 251-287; Moulin in R.G. XIV. (1907), pp. 417-472; Hershey in A.J. I. (1907), pp. 26-45; Drago in A.J. I. (1907), pp. 692-726.]
[Footnote 220: See Scott in A.J. II. (1908), pp. 78-94.]
[Sidenote: Admissibility of Intervention in default of Right.]
§ 136. In contradistinction to intervention by right, there are other interventions which must be considered admissible, although they violate the independence or the territorial or personal supremacy of the State concerned, and although such State has by no means any legal duty to submit patiently and suffer the intervention. Of such interventions in default of right there are two kinds generally admitted and excused--namely, such as are necessary in self-preservation and such as are necessary in the interest of the balance of power.
(1) As regards interventions for the purpose of self-preservation, it is obvious that, if any necessary violation committed in self-preservation of the International Personality of other States is, as shown above (§ 130), excused, such violation must also be excused as is contained in an intervention. And it matters not whether such an intervention exercised in self-preservation is provoked by an actual or imminent intervention on the part of a third State, or by some other incident.
(2) As regards intervention in the interest of the balance of power, it is likewise obvious that it must be excused. An equilibrium between the members of the Family of Nations is an indispensable[221] condition of the very existence of International Law. If the States could not keep one another in check, all Law of Nations would soon disappear, as, naturally, an over-powerful State would tend to act according to discretion instead of according to law. Since the Westphalian Peace of 1648 the principle of balance of power has played a preponderant part in the history of Europe. It found express recognition in 1713 in the Treaty of Peace of Utrecht, it was the guiding star at the Vienna Congress in 1815 when the map of Europe was rearranged, at the Congress of Paris in 1856, the Conference of London in 1867, and the Congress of Berlin in 1878. The States themselves and the majority of writers agree upon the admissibility of intervention in the interest of balance of power. Most of the interventions exercised in the interest of the preservation of the Turkish Empire must, in so far as they are not based on treaty rights, be classified as interventions in the interest of balance of power. Examples of this are supplied by collective interventions exercised by the Powers in 1886 for the purpose of preventing the outbreak of war between Greece and Turkey, and in 1897 during the war between Greece and Turkey with regard to the island of Crete.