We shall go back to the earliest days of the world, and find no dissent from, no qualification of the verdict of the infamy of such acts. Livy says of leagues: "Leagues are such agreements as are made by the command of the supreme power, and whereby the whole nation is made liable to the wrath of God if they infringe it."
Grotius opens his "Admonition," in conclusion of the third book of his famous "Rights of War and Peace," as follows: "'For it is by faith,' saith Cicero, 'that not commonwealths only, but that grand society of nations is maintained.' 'Take away this,' saith Aristotle, 'and all human commerce fails.' It is, therefore, an execrable thing to break faith on which so many lives depend. 'It is,' saith Seneca, 'the best ornament wherewith God hath beautified the rational soul; the strongest support of human society, which ought so much the more inviolably to be kept by sovereign princes by how much they may sin with greater license and impunity than other men. Wherefore take away faith, and men are more fierce and cruel than savage beasts, whose rage all men do horribly dread. Justice, indeed, in all other of her parts hath something that is obscure; but that whereunto we engage our faith is of itself clear and evident; yea, and to this very end do men pawn their faith, that in their negotiations one with another all doubts may be taken away, and every scruple removed. How much more, then, doth it concern kings to keep their faith inviolate, as well for conscience' sake as in regard to their honor and reputation, wherein consists the authority of a kingdom.'"
Vattel says: "Treaties are no better than empty words, if nations do not consider them as respectable engagements, as rules which are to be inviolably observed by sovereigns, and held sacred throughout the whole earth.
"The faith of treaties—that firm and sincere resolution, that invariable constancy in fulfilling our engagements, of which we make profession in a treaty—is therefore to be held sacred and inviolable between the nations of the earth, whose safety and repose it secures; and if mankind be not wilfully deficient in their duty to themselves, infamy must ever be the portion of him who violates his faith. ***
"He who violates his treaties, violates at the same time the law of nations, for he disregards the faith of treaties, that faith which the law of nations declares sacred; and, so far as dependent on him, he renders it vain and ineffectual. Doubly guilty, he does an injury to his ally, and he does an injury to all nations, and inflicts a wound on the great society of mankind. ***
"On the observance and execution of treaties," said a respectable sovereign, "depends all the security which princes and States have with respect to each other, and no dependence could henceforward be placed in future conventions if the existing ones were not to be observed."
It is sometimes said, by those seeking to defend, or at least palliate, the United States Government's repeated disregard of its treaties with the Indians, that no Congress can be held responsible for the acts of the Congress preceding it, or can bind the Congress following it; or, in other words, that each Congress may, if it chooses, undo all that has been done by previous Congresses. However true this may be of some legislative acts, it is clearly not true, according to the principles of international law, of treaties.
On this point Vattel says: "Since public treaties, even those of a personal nature, concluded by a king, or by another sovereign who is invested with sufficient power, are treaties of State, and obligatory on the whole nation, real treaties, which were intended to subsist independently of the person who has concluded them, are undoubtedly binding on his successors; and the obligation which such treaties impose on the State passes successively to all her rulers as soon as they assume the public authority. The case is the same with respect to the rights acquired by those treaties. They are acquired for the State, and successively pass to her conductors."
Von Martens says: "Treaties, properly so called, are either personal or real. They are personal when their continuation in force depends on the person of the sovereign or his family, with whom they have been contracted. They are real when their duration depends on the State, independently of the person who contracts. Consequently, all treaties between republics must be real. All treaties made for a time specified or forever are real. ***
"This division is of the greatest importance, because real treaties never cease to be obligatory, except in cases where all treaties become invalid. Every successor to the sovereignty, in virtue of whatever title he may succeed, is obliged to observe them without their being renewed at his accession."