The Law of Nations or the Principles of Natural Law (1758)

Emmerich de Vattel

Of the Faith of Treaties

§ 218. What is sacred among nations.
THOUGH we have sufficiently established (§§ 163 and 164) the indispensable necessity of keeping promises, and observing treaties, the subject is of such importance, that we cannot forbear considering it here in a more general view, as interesting, not only to contracting parties, but likewise to all nations, and to the universal society of mankind.

Every thing which the public safety renders inviolable is sacred in society. Thus, the person of the sovereign is sacred, because the safety of the state requires that he should be in perfect security, and above the reach of violence: thus the people of Rome declared the persons of their tribunes sacred, — considering it as essential to their own safety that their defenders should be screened from alt violence, and even exempt from fear. Every thing, therefore, which the common safety of mankind and the peace and security of human society require to be held inviolable, is a thing that should be sacred among nations.

§ 219. Treaties are sacred between nations.
Who can doubt that treaties are in the number of those things that are to be held sacred by nations? By treaties the most important affairs are determined; by them the pretensions of sovereigns are regulated; on them nations are to depend for the acknowledgment of their rights, and the security of their dearest interests. Between bodies politic, — between sovereigns who acknowledge no superior on earth, — treaties are the only means of adjusting their various pretensions, — of establishing fixed rules of conduct, — of ascertaining what they are entitled to expect, and what they have to depend on. But 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.

§ 220. The faith of treaties is sacred.
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.

§ 221. He who violates his treaties, violates the law of nations.
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 depends on him, he renders it vain and ineffectual. Doubly guilty, he does an injury to his ally, 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.”1

§ 222. Right of nations against him who disregards the faith of treaties.
As all nations are interested in maintaining the faith of treaties, and causing it to be everywhere considered as sacred and inviolable, so likewise, they are justifiable in forming a confederacy for the purpose of repressing him who testifies a disregard for it, — who openly sports with it, — who violates and tramples it under foot. Such a man is a public enemy who saps the foundations of the peace and common safety of nations. But we should be careful not to extend this maxim to the prejudice of that liberty and independence to which every nation has a claim. When a sovereign breaks his treaties, or refuses to fulfill them, this does not immediately imply that he considers them as empty names, and that he disregards the faith of treaties: he may have good reasons for thinking himself liberated from his engagements; and other sovereigns have not a right to judge him. It is the sovereign who violates his engagements on pretenses that are evidently frivolous, or who does not even think it worth his while to allege any pretense whatever, to give a colorable gloss to his conduct, and cast a veil over his want of faith, — it is such a sovereign who deserves to be treated as an enemy to the human race.

§ 223. The law of nations violated by the popes.
In treating of religion, in the first book of this work, we could not avoid giving several instances of the enormous abuses which the popes formerly made of their authority. There was one in particular, which was equally injurious to all states, and subversive of the law of nations. Several popes have undertaken to break the treaties of sovereigns; they carried their daring audacity so far as to release a contracting power from his engagements, and to absolve him from the oaths by which he had confirmed them. Cesarini, legate of pope Eugenius the Fourth, wishing to break the treaty which Uladislaus, king of Poland and Hungary, had concluded with the sultan Amurath, pronounced, in the pope’s name, the king’s absolution from his oaths.2 In those times of ignorance, people thought themselves really bound by nothing but their oaths, and they attributed to the pope the power of absolving them from oaths of every kind. Uladislaus renewed hostilities against the Turks: but that prince, in other respects worthy of a better fate, paid dearly for perfidy, or rather for his superstitious weakness: he perished, with his army, near Varna; — a loss which was fatal to Christendom, and brought on her by her spiritual head. The following epitaph was written on Uladislaus:

      Romulidæ Cannas, ego Varnam clade notavi.
      Discite, mortales, non temerare fidem.
      Me nisi pontifices jussissent rumpere foedus,
      Non ferret Scythicum Pannonis ora jugum.

Pope John XII. declared null the oath which the emperor Louis of Bavaria, and his competitor Frederic of Austria, had mutually taken when the emperor set the latter at liberty. Philip, duke of Burgundy, abandoning the alliance of the English, procured from the pope and the council of Basil an absolution from his oath. And at a time when the revival of letters, and the establishment of the Reformation should have rendered the popes more circumspect, the legate Caraffa, in order to induce Henry II. of France to a renewal of hostilities, had the audacity to absolve him, in 1556, from the oath he had made to observe the truce of Vaucelles.3 The famous peace of Westphalia displeasing the pope on many accounts, he did not confine himself to protesting against the articles of a treaty in which all Europe was interested: he published a bull, in which, from his own certain knowledge, and full ecclesiastical power, he declared several articles of the treaty null, vain, invalid, iniquitous, unjust, condemned, reprobated, frivolous, void of force and effect; and that nobody was bound to observe them or any of them, though they were confirmed by oath. — Nor was this all: — his holiness, assuming the tone of an absolute master, proceeds thus — And, nevertheless, for the greater precaution, and as much as need be, from the same motions, knowledge, deliberations, and plenitude of power, we condemn, reprobate, break, annul, and deprive of ail force and effect, the said articles, and all the other things prejudicial to the above, etc.4 Who does not see that these daring acts of the popes, which were formerly very frequent, were violations of the law of nations, and directly tended to destroy all the bands that could unite mankind, and to sap the foundations of their tranquillity, or to render the pope sole arbiter of their affairs?

§ 224. This abuse authorized by princes.
But who can restrain his indignation at seeing this strange abuse authorized by princes themselves? In the treaty concluded at Vincennes, between Charles V. king of France, and Robert Stuart, king of Scotland, in 1371, it was agreed that the pope should absolve the Scots from all the oaths they had taken in swearing to a truce with the English, and that he should promise never to absolve the French or Scots from the oaths they were about to make in swearing to the new treaty.5

§ 225. Use of an oath in treaties. It does not constitute the obligation.6
The custom generally received in former times, of swearing to the observance of treaties, had furnished the popes with a pretext for claiming the power of breaking them, by absolving the contracting parties from their oaths. But, in the present day, even children know that an oath does not constitute the obligation to keep a promise or a treaty: it only gives an additional strength to that obligation by calling God to bear witness. A man of sense, a man of honor, does not think

himself less bound by his word alone, by his faith once pledged, than if he had added the sanction of an oath. Cicero would not have us to make much difference between a perjurer and a liar. “The habit of lying (says that great man) paves the way to perjury. Whoever can be prevailed on to utter a falsehood, may be easily won over to commit perjury: for the man who has once deviated from the line of truth, generally feels as little scruple in consenting to a perjury as to a lie. For, what influence can the invocation of the gods have on the mind of him who is deaf to the voice of conscience? The same punishment, therefore, which heaven has ordained for the perjurer, awaits also the liar: for it is not on account of the formula of words in which the oath is couched, but of the perfidy and villainy displayed by the perjurer in plotting harm against his neighbor, that the anger and indignation of the gods is roused.”7

The oath does not then produce a new obligation: it only gives additional force to the obligation imposed by the treaty, and in every thing shares the same fate with it. Where the treaty is of its own nature valid and obligatory, the oath (in itself a supererogatory obligation) is so too: but, where the treaty is void, the oath is void likewise.

§ 226. It does not change the nature of obligations.
The oath is a personal act: it can therefore only regard the person of him who swears, whether he swears himself, or deputes another to swear in his name. However, as this act does not produce a new obligation, it makes no change in the nature of a treaty. Thus, an alliance confirmed by oath is so confirmed only with respect to him who has contracted it: but if it be a real alliance, it survives him, and passes to his successors as an alliance not confirmed by oath.

§ 227. It gives no pre-eminence to one treaty above another.
For the same reason, since the oath can impose no other obligation than that which results from the treaty itself, it gives no pre-eminence to one treaty, to the prejudice of those that are not sworn to. And as, in case of two treaties clashing with each other, the more ancient ally is to be preferred (§ 167); the same rule should be observed, even though the more recent treaty has been confirmed by an oath. In the same manner, since it is not allowable to engage in treaties inconsistent with existing ones (§ 165), the circumstance of an oath will not justify such treaties, nor give them sufficient validity to supersede those which are incompatible with them: — if it had such an effect, this would be a convenient mode for princes to rid themselves of their engagements.

§ 228. It cannot give force to a treaty that is invalid.
Thus also an oath cannot give validity to a treaty that is of its own nature invalid, — justify a treaty which is in itself unjust, — or impose any obligation to fulfill a treaty, however lawfully concluded, when an occasion occurs in which the observance of it would be unlawful, — as for instance, if the ally to whom succors have been promised undertakes a war that is manifestly unjust. In short, every treaty made for a dishonorable purpose (§ 161), every treaty prejudicial to the state (§ 160), or contrary to her fundamental laws (Book I. § 265), being in its own nature void, — the oath that may have been added to such a treaty is void likewise, and falls to the ground together with the covenant which it was intended to confirm.

§ 229. Asseverations.
The asseverations used in entering into engagements are forms of expression intended to give the greater force to promises. Thus, kings promise in the most sacred manner, with good faith, solemnly, irrevocably, and engage their royal word, etc. A man of honor thinks himself sufficiently bound by his word alone: yet these asseverations are not useless, inasmuch as they tend to prove that the contracting parties form their engagements deliberately, and with a knowledge of what they are about. Hence, consequently the violation of such engagements become the more disgraceful. With mankind, whose faith is so uncertain, every circumstance is to be turned to advantage: and since the sense of shame operates more powerfully on their minds that the sentiment of duty, it would be imprudent to neglect this method.

§ 230. The faith of treaties does not depend on the difference of religion.
After what we have said above (§ 162), it were unnecessary to undertake in this place to prove that the faith of treaties has no relation to the difference of religion, and cannot in any manner depend upon it. The monstrous maxim, that no faith is to be kept with heretics, might formerly raise its head amidst the madness of party and the fury of superstition: but it is at present detested.

§ 231. Precautions to be taken in wording treaties.
If the security of him who stipulates for anything in his own favor prompts him to require precision, fulness, and the greatest clearness in the expressions, — good faith demands, on the other hand, that each party should express his promises clearly, and without the least ambiguity. The faith of treaties is basely prostituted by studying to couch them in vague or equivocal terms, to introduce ambiguous expressions, to reserve subjects of dispute, to overreach those with whom we treat, and outdo them in cunning and duplicity. Let the man who excels in these arts boast of his happy talents, and esteem himself a keen negotiator, but reason and the sacred law of nature will class him as far beneath a vulgar cheat as the majesty of kings is exalted above private persons. True diplomatic skill consists in guarding against imposition, not in practicing it.

§ 232. Subterfuges in treaties.
Subterfuges in a treaty are not less contrary to good faith. His catholic Majesty, Ferdinand, having concluded a treaty with the archduke his son-in-law, thought he could evade it by privately protesting against the treaty: a puerile finesse! which, without giving any right to that prince, only exposed his weakness and duplicity.

§ 233. An evidently false interpretation inconsistent with the faith of treaties.
The rules that establish a lawful interpretation of treaties are sufficiently important to be made the subject of a distinct chapter. For the present, let us simply observe that an evidently false interpretation is the grossest imaginable violation of the faith of treaties. He that resorts to such an expedient either impudently sports with that sacred faith, or sufficiently evinces his inward conviction of the degree of moral turpitude annexed to the violation of it: he wishes to act a dishonest part, and yet preserve the character of an honest man: he is a puritanical impostor, who aggravates his crime by the addition of a detestable hypocrisy. Grotius quotes several instances of evidently false interpretations put upon treaties:8 The Plateans, having promised the Thebans to restore their prisoners, restored them after they had put them to death. Pericles, having promised to spare the lives of such of the enemy as laid down their arms,9 ordered all those to be killed who had iron clasps to their cloaks. A Roman general,10 having agreed with Antiochus to restore him half of his fleet, caused each of the ships to be sawed in two. All these interpretations are as fraudulent as that of Rhadamistus, who, according to Tacitus’s account,11 having sworn to Mithridates that he would not employ either poison or the steel against him, caused him to be smothered under a heap of clothes.

§ 234. Faith tacitly pledged.
Our faith may be tacitly pledged, as well as expressly: it is sufficient that it be pledged, in order to become obligatory; the manner can make no difference in the case. The tacit pleading of faith is founded on a tacit consent; and a tacit consent is that which, is, by fair deduction, inferred from our actions. Thus, as Grotius observes,12 whatever is included in the nature of certain acts which are agreed upon, it is tacitly comprehended in the agreement: or, in other words, every thing which is indispensably necessary to give effect to the articles agreed on, is tacitly granted. If, for instance, a promise is made to a hostile army who have advanced far into the country, that they shall be allowed to return home in safety, it is manifest that they cannot be refused provisions; for they cannot return without them. In the same manner, in demanding or accepting an interview, full security is tacitly promised, Livy justly says, that the Gallo-Greeks violated the law of nations in attacking the consul Manlius at the time when he was repairing to the place of interview to which they had invited him.13 The emperor Valerian, having been defeated by Sapor, King of Persia, sent to him to sue for peace. Sapor declared that he wished to treat with the emperor in person; and Valerian, having consented to the interview without any suspicion of fraud, was carried off by the perfidious enemy, who kept him a prisoner till his death, and treated him with the most brutal cruelty.14

Grotius, in treating of tacit conventions, speaks of those in which the parties pledge their faith by mute signs.15 But we ought not to confound these two kinds of tacit conventions: for that consent which is sufficiently notified by a sign, is an express consent, as clearly as if it had been signified by the voice. Words themselves are but signs established by custom: and there are mute signs which established custom renders as clear as express as words. Thus, at the present day, by displaying a white flag, a parley is demanded, as expressly as it could be done by the use of speech. Security is tacitly promised to the enemy who advances upon this invitation.


     1.    Resolution of the States-general, of the 15th of March, 1726, in answer to the Memorial of the Marquis de St. Philip, Ambassador of Spain.
     2.    History of Poland, by the Chevalier de Solignac, vol. iv. 112. He quotes Dlugoss, Neugobauer, Sarnicki, Herburt, De Fulstin. etc.
     3.    On these facts, see the French and German historians. — “Thus war was determined on in favor of the pope: and after cardinal Caraffia, by virtue of the powers vested in him by his holiness, had absolved the king from the oaths he had taken in ratification of the truce, he even permitted him to attack the emperor and his son without a previous declaration of hostilities.” — De Thou, lib. svii.
     4.    History of the Treaty of Westphalia, by Father Bougeant, in 12 mo. vi. p. 413.
     5.    Choisy’s History of Charles V. p. 282.
     6.    Paley, in his Moral Philosophy, agrees in this view of moral obligation. It is the modern policy to restrain prospective oaths, or rather promises, and all extra-judicial oaths not essential for eliciting evidence upon past events. — C.
     7.    At quid interest iter perjurum el mendacem? Qui mentiri solet, pejerare consuevit. Quem ego, ut menitiatur, inducere possum, ut pejeret, exorare facile potero: nam qui semel a veritate deflexit, hic non majori religione ad perjurium quam ad mendacium perduci consuevit. Quis enim deprecatione decorum, non conscientiæ fide commoveutri? Propterea, quæ pœ na ab diis immortalibus perjaro, hæc eadem mendaci constituta est. Non enim ex pactione verborum quibus jusjurandum comprehenditur, sed ex perfidia et malitia per quam insidiæ tenduntur alicui, dii immortales hominibus irasci et succensere consuerunt. Cicer. Orat. pro Q. Roscio, comœ do.
     8.    De Jure Belli et Pads, lib. ii. cap. xvi. § 5.
     9.    Literally, “laid down their iron or steel:” hence the perfidious quibble on the word iron, which cannot be so well rendered in English.
     10.    Q. Fabvius Labeo, according to Valerius Maximus; Livy makes no mention of the transaction.
     11.    Annal. lib. xii.
     12.    Lib. iii. cap. xxiv. § 1.
     13.    Livy, lib. xxxviii. cap. xxv.
     14.    The Life of Valerian in Crevier’s History of the Emperors.
     15.    Lib. iii. cap. xxiv. § 5.