Casus foederis

Lat. The case of the treaty or compact; the case or event contemplated by a treaty; a case within it, or to which it applies.

1 Kent's Com. 49.

Applied to an exigency contemplated by the constitution of the United States, (the foedus of the union.) Id. 264. Applied also to an ordinary contract, as to a respondentia bond.

Story, J., 4 Mason's R. 253.