The law of nations , is a jurisprudence which natural reason has established over certain matters between all men, and which is observed among all nations. It is also sometimes called public law of nations or simply public law ; but we also distinguish two sorts of public law , the one general which is common to all nations, and the other particular which is proper to a single state, the term law of nations being the older and more widely used, to denote the law which is common to all nations.

Roman laws distinguish natural law from the law of nations ; and indeed the first term considered in its broadest sense, is a certain sentiment [1] which nature breathes into all animals as well as men.

But if we consider the natural law which is proper to man, and which is founded solely on the lights of reason, of which beasts are incapable, it must follow that from this perspective the law of nature is the same thing as the law of nations , both being founded on the natural lights of reason: thus we see that most authors who have written on this matter have confounded these two subjects; such as the baron de Pufendorf, who titled his work le droit de la nature et des gens: ou système général de la morale, de la jurisprudence, et de la politique [ the law of nature and of nations: or general system of moral reasoning, jurisprudence, and politics ]. [2]

Among the Romans, two sorts of laws of nations were also distinguished; namely, the older one called primarium [primary], the other secundarium [secondary]. [3]

The law of nations called primarium , that is to say ‘primitive’ or ‘older’, is properly the only one which natural reason has instilled in men; as in the devotion which one renders to God, the respect and submission which children have for their father and mother, the attachment which citizens have for their country, the good faith that must be the spirit of treaties, and many other similar things.

The law of nations called secundarium , consists of certain customs which established themselves among men with the passage of time, insofar as the need for them was felt.

The effects of the law of nations with respect to people, are the distinction of cities and states, the law of war and of peace, slavery, and many other similar things. Its effects with respect to goods are, the distinction of estates, the relations which men have among themselves in commerce and in other needs of life; and the majority of contracts, which draw their origin from the law of nations , and are called contrats du droit des gens [contracts iuris gentium or contracts of the law of nations], because they are equally customary among all nations: such as contracts of sale, of exchange, of lodging, of renting, etc. [4]

We see by what was just said, that the law of nations applies not only to that which is part of general public law, and to that which concerns the relations which different nations have with one another, but also to certain customs in private law, which are also considered to be of the law of nations , because these customs are common to all nations, such as the different contracts of which we have made mention; but when one speaks simply of the law of nations , one usually understands this as the public law of nations .

The primitive law of nations is as old as man; and it is so tied with natural law, which is unique to men, that it is by its essence as invariable as natural law. Religious rituals may change, but the devotion one owes to God observes no change at all: it is the same with the duties of children toward their fathers and mothers, or of citizens toward the nation, and with the good faith necessary among contracting parties; and if these duties are not always entirely well-fulfilled, at least they ought to be, and they are of an invariable nature.

Regarding the second law of nations called by the Romans secundarium , this one was exclusively formed, as has already been said, with the passage of time, as the need for it was felt: thus reciprocal obligations among citizens began when men established cities in order to live in society; the duties of subjects toward the state began, when men of each locality who composed among themselves but a single family, subject only to paternal government, established above themselves a public authority, which they delegated to one or several among themselves.

Ambition, interests, and other subjects of disagreement between neighboring powers, have given rise to wars and slavery; such are the grim sources of part of this second law of nations .

Different nations, although the majority are divided in their interests, tacitly agree among themselves to observe, in peace and in war alike, certain rules of propriety, of humanity, and of justice: such as never to attack the person of ambassadors, or others sent to make proposals of peace or of truce; never to poison fountains; to respect temples; to spare women, the elderly, and children: these customs and many others like them, which with the passage of time have acquired the force of law, have formed what we call the law of nations , or law common to different peoples.

However, civilized nations have more rights in common with certain peoples than others, according to how much these peoples are themselves more or less civilized, and whether they are familiar with the laws of humanity, justice, and honor.

For example, with cannibalistic savages, who live in a profound ignorance and without formal government, there is little communication, and hardly any assurance on their part. It is permitted for other men to defend themselves against them, even by force, as against wild beasts; one must nonetheless never harm them without necessity: one may dwell in their country to cultivate it, and if they wish to trade with us, instruct them in the true faith, and communicate to them the conveniences of life.

Among Barbarians who live in the form of a state, one may trade and do all other things which they permit, as one would do with more cultivated peoples.

With infidels one may do anything that would not tend to condone their religion, or injure or pervert our own.

The various Muslim nations, though the majority are attached to different sects and subject to different powers, have among them many common laws which constitute their law of nations , the Qur’an being the foundation of all their laws, even the temporal ones.

Christians, when they are at war with one another, take prisoners, as do other nations; but they never treat their prisoners as slaves: it is also a law among them to provide mutual assistance against infidels.

The law of nations which is observed presently in Europe, is formed from many customs derived in part from the Romans, in part from Germanic laws, and has arrived only gradually to the point of perfection where it is today.

The Germans, from whom the Francs were descended, hardly yet recognized any law of nations by the time of Tacitus; thus this author, in speaking of the manners of these peoples, said that their entire policy with respect to foreigners, consisted of openly seizing from their neighbors the fruits of their labor, having as a maxim that it would have been cowardly only to acquire things through toil and sweat, which one could have had instantly at the price of blood. [5]

The laws and customs of France spread from the time of Charlemagne throughout Italy, Spain, Sicily, Hungary, Germany, Poland, Sweden, Denmark, and England, and generally through all of Europe, excepting that part subjected to the authority of Constantinople. In all of these countries the name of roman emperor had always been respected; and he who possessed the title, held the first rank among sovereigns. One notes also that in the different states of Europe we use virtually the same titles of dignity; that in each state there is a king or another sovereign; that the principal lords bear everywhere the same titles of prince, duke, count, etc.; that officials bear also the same titles of constable, chancellor, marshal, admiral, seneschal, [6] etc.; that there are everywhere rather similar public assemblies, under the names of parliaments, estates, diets, councils, chambers, etc.; that everywhere we maintain in these assemblies the distinctions of the different orders, such as the clergy, the nobility, and the third estate; that of the robe and the sword, that of the nobles from the commoners: in a word that every form of government in Europe is drawn from the same model; which comes from the fact that these people were all subjects of Charlemagne, or his neighbors, who considered it glorious to imitate him.

It is thus on this basis that many of those who have treated public law or the law of nations of Europe, say that the true origin of this law dates only to the time of Charlemagne, because in effect the various nations of Europe were thitherto little civilized, and observed few rules among themselves. It is in this memorable epoch of the reign of Charlemagne, that the universal corpus of the law of nations , by Jean Dumont, begins, which contains in seventeen volumes in-folio all the treaties of alliance, of peace, of navigation and of commerce, and other acts relating to the law of nations from the time of Charlemagne. [7]

Others contend that one should only begin a study of the law of nations from the time of the emperor Maximilian I, of Louis XI, and of Ferdinand the Catholic, both kings, one of France, the other of Spain; that all which is found before these times serves less for instruction than for curiosity and that it is only from the time of these princes that we see a well-formed and well-established politics. See l'Europe pacifiée par l'équité de la reine de Hongrie [ Europe pacified through the fair judgment of the queen of Hungary ], p. 5. [8]

What this author says would be true, if one only understood the term politics to mean the science of living with neighboring peoples, and the rules which one ought to observe with them; but following the idea which is commonly attached to the term politics , there is a certain prudence peculiar to government, as much for domestic as for external affairs: it is the art of knowing the true interests of the state, and those of neighboring powers; of concealing ones plans, of anticipating and disrupting those of enemies; now in this sense politics differs totally from the public law of nations , which is nothing more than certain rules observed by all nations among themselves, with respect to their reciprocal relations.

The treatise of Grotius, de jure belli ac pacis [ on the law of war and peace ], which, following the title, seems only to be about the laws of war, which in effect comprise its principle object, nonetheless also includes the principles of natural law and those of the law of nations . It treats therein right in general, [9] laws common to all men, different modes of acquisition, of marriage, of the power of fathers over their children, that of masters over their slaves, and of sovereigns over their subjects, of promises, contracts, oaths, public conventions, of the rights of ambassadors, the laws of burial; of punishments, and other matters which concern the law of nations . Even the laws of war and peace are part of it; this is why it examines what war is, in which cases it is just; what is permitted to do in war, how one ought to keep one’s word with enemies, and in what manner one ought to treat the conquered.

But while this work contains excellent things on the law of nations , we cannot regard it as a methodical treatise on this law in general; and this is certainly what led Pufendorf to compose his treatise de jure naturae et gentium [ on the law of nature and of nations ], in which he observed a greater order in the arrangement of topics. Like that of Grotius, this treatise has been translated into French by Barbeyrac and accompanied by very useful commentaries: we will present here a brief analysis of it, nothing being better suited to give an adequate idea of the issues which encompass the law of nations .

The author (Pufendorf) in the first book first seeks the source of natural law and that of nations in the essence of moral beings, [10] of which he examines the origin and the different varieties. He calls moral beings certain arrangements which intelligent beings attach to natural events or to physical movements: with a view to guiding and restraining man’s scope for voluntary action, and to bring about some order, some congruence, and some beauty to human life, he examines what one ought to think regarding the certainty of moral sciences, how human understanding and will are principles of moral action: he then treats moral actions in general, and the role of the agent in them, or that which makes them capable of imputation; the order which guides moral action, and law in general; the qualities of moral action, the quantity and the worth of these actions, and their actual imputation. [11]

After these preliminary considerations on everything related to morality, the author, in the second book, considers the state of nature, and the general foundations of natural law itself. He holds that it is not consistent with man’s nature to live without some law: then he examines particularly what the state of nature is, and what natural law is in general; what the duties of man are to himself, as much with respect to the care of his soul, as with respect to the health of his body and life; to what point the legitimate defense of one’s self extends, and the rights and privileges of necessity.

Up to this point he only addresses natural law ; but in the third book the author seems to have in mind the law of nations : in effect, he considers in general the necessary duties of men toward one another, and promises or conventions in general. The principles which he establishes are that one ought never to do wrong unto anyone; that if one has caused anyone harm, one ought to compensate for it; that all men ought to regard one another as equals by nature, and here he explains the common duties of humanity; with what inviolable faithfulness one should keep to one’s word and fulfill various sorts of obligations; what the nature of promises and conventions in general is, what comprises their substance, and what consent they require; the conditions and other clauses which one may add to contracts, and how one may contract through a representative.

The fourth book appears to address two principal subjects; the first is the obligation involved in giving one’s word and taking oaths: he also treats here the nature of lying. The other subject is the right of property, and the different modes of acquisition: he explains here the rights of men over things, the origin of the ownership of goods, the things which may enter into ownership, the acquisition which arises through the right of first occupant, [12] and through that of accession; [13] the right which one may have to the property of another, the different ways of alienating it; dispositions of wills, inheritances ab intestat [in testate or without a will], time limits [ prescription ], lastly the duties which result from ownership of goods considered in itself, and above all what is required of a proprietor of good faith.

Pufendorf then treats in the 5th book, the price of things, contracts in general; the equality which must exist in those contracts which he calls with interests on both sides , that is to say those which are synallagmatic; [14] contracts which contain some flexibility; contracts of exchange and sale, which are the first two types of synallagmatic contracts; contracts of rent, of loan for consumption, which is what is called in law a mutuum [loan], and contracts of the interests of a corporation; [15] insurance contracts, ancillary agreements; how one is freed from commitments into which one has personally entered; in what manner one ought to interpret conventions and laws, and how to resolve the disputes arising between those who live in the state of natural freedom.

The sixth book concerns marriage, paternal authority, and the power of masters over their servants or their slaves.

The seventh treats the motives which have brought men to form civil societies, the interior constitution of states, the origin and the foundations of sovereignty, its elements and their natural relationship, the various forms of government, the unique characteristics and changes of sovereignty, the different means of acquiring it, lastly the rights and duties of the sovereign.

In the eighth and last book the author discusses the legislative authority which belongs to sovereigns, that which they have over the lives of their subjects on the occasion of the defense of the state, and that which they have over the lives and the goods of their subjects for the punishment of crimes and transgressions. He also treats esteem in general, and the power which sovereigns have to regulate the degree of esteem and the consideration in which each citizen ought to be held; [16] in what case they can dispose of the domain of the state and the property of individuals. The law of war, which is also one of the subjects of this book, is the sole concern of Grotius’ treatise. The agreements which one makes with enemies during war, those which purport to reestablish peace, are also discussed by Pufendorf. He concludes this book with that which concerns alliances and public agreements made without the order of the sovereign, contracts and other conventions or promises of kings; how one ceases to be a citizen or subject of a state, lastly the changes and the destruction of states.

Such is Puffendorf’s system, and the structure which he has followed in his treatise; a work full of erudition, and undoubtedly very useful, but in which there are many things inconsistent with our customs, such as what he says regarding the right of first occupant with respect to hunting; [17] and on marriage, particularly divorce, with respect to which he seems excessively relaxed. [18]

M. Burlamaqui, in his principes du droit naturel [ principles of natural law ], also touches somewhat on the law of nations , and particularly in chapter vi of the second part, where he examines how civil societies form, and demonstrates that the civil state in no way destroys the natural state; that it does nothing but perfect it. [19] He discusses what the law of nations is, the certainty of this law . He distinguishes two sorts of law of nations , the one necessary and obligatory in itself, the other arbitrary and according to convention. He also discusses the view of Grotius with respect to the law of nations . We will discuss this treatise later at further length, with respect to natural law . See also the codex juris gentium diplomaticus [ diplomatic code of the law of nations ] of Leibnitz, and the following entry on Droit public. [20]

1. That is, a faculty of feeling or compassion, distinct from a faculty of moral reasoning

2. Morale is also sometimes translated as “moral science”: see for example the title page in Pufendorf, Of the law of nature and nations (1672), ed. Barbeyrac, trans. Basil Kennett (London, 1729). All subsequent parenthetical citations refer to this edition, unless otherwise noted.

3. That is, ius gentium primarium (primary law of nations) and ius gentium secundarium (secondary law of nations). Although the concept of the existence of primary and secondary laws of nations is here attributed to Roman law, it was substantially developed by medieval and early modern European authors, particularly Hugo Grotius. For Grotius’ explanation of the primary and secondary laws of nations, see Grotius. Commentary on the law of prize and booty (1603), ed. Martine Julia van Ittersum. 2006, chap. ii; for a summary of the history of the concept of the secondary law of nations, see Anthony Pagden. The Burdens of Empire: 1539 to the Present (New York: Cambridge UP, 2015).

4. The Roman legal concept of “contracts of the law of nations” here is analogous to modern private international law. The use of the Latin legal term (i.e., contracts iuris gentium ) is usually preferred in English sources over the literal translation, favored here by Boucher d’Argis and some of his French contemporaries (i.e., contrats du droit des gens ). For elaboration on Roman contract law and its later influence on private international law, see Bozeman, Politics and culture in international history , 2d ed. (New Brunswick, NJ: Transaction Publishers, 1960), 209-10.

5. For the passage containing this maxim, see Tacitus, Germany , ch. 14. in The Agricola and Germany of Tacitus , trans. Church and Brodribb (London, 1868), 11.

6. Term for a regional head of justice or bailiff.

7. See Corps universal diplomatique du droit des gens, ed. Jean Dumont (1726-39).

8. See Nicolas Lenglet Du Fresnoy, L’Europe pacifiée par l’équité de la reine de Hongrie, ou distribution légale de la succession d’Autriche (Brussels, 1745).

9. Droit is sometimes translated as ‘right’ rather than ‘law’ in translations of Grotius and other writers, particularly when ‘right’ is understood abstractly as part of a faculty of moral reasoning. Thus in Barksdale’s Grotius: “For I profess sincerely, as Mathematicians consider Figures abstract from Bodies, so have I in treating of Right, elevated my Meditations above all particular Actions”; and in Kennett’s Pufendorf: “Right is the moral quality by which we justly obtain either the Government of Persons, or the Possession of Things, or by the Force of which we may claim somewhat as due to us.” See Preface to Grotius. Of the law of warre and peace (1625), trans Barksdale (London, 1655); “Preliminary discourse concerning the certainty of right in general,” in Grotius. The Rights of War and Peace, ed. Richard Tuck (Indianapolis, 2005); Pufendorf. Of the Law of Nature, 1.1.20, p. 12; Kant, “Metaphysical first principles of the doctrine of right,” in Metaphysics of morals (1797), trans. Gregor (1991); Hegel, Philosophy of right (1820), trans. Dyde (1896).

10. Translated by Kennett as “moral entities” (1.1. p. 1); though Pufendorf’s Latin original prefers ‘moral being’ ( ens morale ) over ‘moral entity’ ( entitas moralis ); see Pufendorf. De iure naturae et gentium (1672), ed. Barbeyrac (Frankfurt and Leipzig, 1759), bk. I, p. 3.

11. Imputation, that is, ascription of responsibility for an action to someone.

12. The ‘right of first occupant’ is a technical term from Roman law, frequently expressed in English without the definitive article, similar to terms like the ‘right of first refusal’. See Jean-Jacques Rousseau, Social contract, (1762), trans. Tozer (1998), 21.

13. According to the principle of accession, “whoever is the owner of a thing, to him likewise belong the accessions of it”, i.e. the fruits of it, the ‘accessory’ or ‘accession’ being the fruit. For Pufendorf’s elaboration of this principle, see Pufendorf, Of the Law of Nature, 4.7.2, 397.

14. Synallagmatic contracts are those in each which each party is bound to provide something to the other party. The term derives for the Greek word meaning “mutual agreement.”

15. That is, a corporate charter.

16. “Pufendorf uses the concept of  existimatio  to refer to comparative moral quantities among people. Unlike Hobbes, who defines the value of persons as ‘price’ (Leviathan 10), Pufendorf differentiates the value of persons termed ‘esteem’ ( existimatio ) from the value ( valor ) of things, which he calls ‘price’ ( pretium ). Esteem is ‘the value of persons in communal life according to which they can be equated or compared with others, and ranked before or after them’ (Of the Law of Nature, 253).” Haara and Lahdenranta, “Smithian sentimentalism anticipated: Pufendorf on the desire for esteem and moral conduct,” Journal of Scottish philosophy 16(1), n. 6.

17. for the passage cited, see Of the Law of Nature, 4.6.10, p. 392.

18. For the relevant passages on divorce in Pufendorf, see Of the Law of Nature, 6.1.20-4. For more on Pufendorf’s views on divorce, see Hoffman. La Femme dans la pensée des lumières (Strasbourg, 1977), 276-77; Rosenblatt. “Milton, natural law, and toleration,” in Milton & Toleration , ed. Achinstein and Sauer (New York: Oxford UP, 2007), 140-2; S.B. Kitchin, A history of divorce (London, 1910), 135-7; and Achinstein, “Early modern marriage in a secular age: beyond the sexual contract,” in Milton in the Long Restoration , ed. Hoxby and Coiro (New York: Oxford UP, 2016), 375-66.

19. See Jean-Jacques Burlamaqui, The Principles of Natural and Political Law (1747) trans. Thomas Nugent (1763), pt. ii. ch. vi.

20. For the preface to Leibniz’s codex iurs gentium see Leibniz, Political writings , trans. Patrick Riley (New York: Cambridge UP, 1988), 165-76.