Casus foedoris

CASUS FOEDORIS. When two nations have formed a treaty of alliance, in anticipation of a war or other difficulty with another, and it is required to determine the case in which the parties must act in consequence of the alliance, this is called the casus foederis, or case of alliance. Vattel, liv. 3, c. 6, Sec. 88.

A Law Dictionary, Adapted to the Constitution and Laws of the United States. By John Bouvier. Published 1856.