Casus Fœderis.
§ 573. Casus fœderis is the event upon the occurrence of which it becomes the duty of one of the allies to render the promised assistance to the other. Thus in case of a defensive alliance the casus fœderis occurs when war is declared or commenced against one of the allies. Treaties of alliance very often define precisely the event which shall be the casus fœderis, and then the latter is less exposed to controversy. But, on the other hand, there have been many alliances concluded without such specialisation, and, consequently, disputes have arisen later between the parties as to the casus fœderis.
That the casus fœderis is not influenced by the fact that a State, subsequent to entering into an alliance, concludes a treaty of general arbitration with a third State, has been pointed out above, § [522].
III TREATIES OF GUARANTEE AND OF PROTECTION
Vattel, II. §§ 235-239—Hall, § 113—Phillimore, II. §§ 56-63—Twiss, I. § 249—Halleck, I. p. 285—Taylor, §§ 350-353—Wheaton, § 278—Bluntschli, §§ 430-439—Heffter, § 97—Geffcken in Holtzendorff, III. pp. 85-112—Liszt, § 22—Ullmann, § 83—Fiore, Code, Nos. 787-791—Bonfils, Nos. 882-893—Despagnet, No. 461—Mérignhac, II. p. 681—Nys, III. pp. 36-41—Pradier-Fodéré, II. Nos. 969-1020—Rivier, II. pp. 97-105—Calvo, III. §§ 1584-1585—Martens, I. § 115—Neyron, "Essai historique et politique sur les garanties" (1779)—Milovanovitch, "Des traités de garantie en droit international" (1888)—Erich, "Ueber Allianzen und Allianzverhältnisse nach heutigem Völkerrecht" (1907)—Quabbe, "Die völkerrechtliche Garantie" (1911).
Conception and Object of Guarantee Treaties.
§ 574. Treaties of guarantee are conventions by which one of the parties engages to do what is in its power to secure a certain object to the other party. Guarantee treaties may be mutual or unilateral. They may be concluded by two States only, or by a number of States jointly, and in the latter case the single guarantors may give their guarantee severally or collectively or both. And the guarantee may be for a certain period of time only or permanent.
The possible objects of guarantee treaties are numerous.[940] It suffices to give the following chief examples: the performance of a particular act on the part of a certain State, as the discharge of a debt or the cession of a territory; certain rights of a State; the undisturbed possession of the whole or a particular part of the territory; a particular form of Constitution; a certain status, as permanent neutrality[941] or independence[942] or integrity[943]; a particular dynastic succession; the fulfilment of a treaty concluded by a third State.
[940] The important part that treaties of guarantee play in politics may be seen from a glance at Great Britain's guarantee treaties. See Munro, "England's Treaties of Guarantee," in The Law Magazine and Review, VI. (1881), pp. 215-238.