Note 36 — Chapter XII · On Contracts.

There is a distinction to be observed between the NECESSARY, and the VOLUNTARY law of nations. Vattel defines the NECESSARY law to be "that which is always obligatory on the conscience, and of which a nation ought never to lose sight in the line of conduct she is to pursue in order to fulfil her duty, but when there is a question of examining what she may demand of other states, she must consult the Voluntary law, whose maxims are devoted to the safety and advantage of the universal society of mankind."—Prelim. sect. 28.