The strict theory of Roman law which remained throughout its history was that the ius civile was only for citizens, and, as there was originally no other law than the ius civile, the foreigner was both rightless and dutiless. It was open to any Roman to seize him and his property as things without an owner, and, on the other hand, there was no court in which he could be sued. Whether there was ever a time at which practice was entirely in consonance with this theory may be doubted, but at any rate as soon as intercourse with other states became at all common and civilisation advanced, such a barbarous system could no longer be maintained.
We have seen that an exception was made in the case of members of the Latin league, whose admission to commercium means that their rights were protected at Rome, and very early history already provides an example of a treaty with a foreign state which guarantees mutual protection of legal rights, at least so far as they arise out of commerce. This is the treaty said to have been concluded in the first year of the republic (509 B.C.) between Rome and Carthage. Unfortunately we have no record of the nature of the protection granted in this treaty, but other treaties appear to have made provision for reciperatio, i.e. the appointment of a court of several jurymen (recuperatores), perhaps taken from nationals of both the states concerned. Finally, quite apart from special treaties, the foreigner was no longer in fact treated as rightless; to treat him so would have been to put a stop to the possibility of commerce, and the commercial interests of Rome were growing. We have seen that about 242 B.C. a special praetor was appointed to deal with disputes in which foreigners were concerned, and from our accounts there can be no doubt that the single praetor had been dealing with such cases, as well as those in which citizens alone were involved, for some time previously. About the same time, it must be remembered, Rome also acquired her first provinces, which meant that her governors would have to concern themselves with jurisdiction abroad in which foreigners would necessarily be involved.
Two questions arise in connection with the courts in which a Roman magistrate exercised jurisdiction over foreigners; first as to the procedure used and secondly as to the law applied. The strictly Roman legis actio procedure was not available, and the magistrate would have to find some method for himself. Very probably the comparatively flexible formulary procedure, which appears to have been based on Greek precedents, was first introduced in these courts, but its origin is too uncertain for us to speak with any confidence. The law of course could not be the ius civile pure and simple because that applied to citizens only, and probably the foreigners concerned were far from eager that it should be extended to them in its entirety; its cumbrous formalities, in which a single slip might mean disaster, would be particularly unattractive to those who came from Greek states and were used to a more developed and freer system. The problem might have been solved by applying the principle of personality, i.e. of judging a man according to the law of his own state, and to some extent this was done. Foreigners belonging to the same state were, we know, generally allowed to settle their disputes according to the law of that state when they cam before the local courts, and it is probable that the same principle applied if the matter was litigated before the Roman governor's tribunal. But if this principle had been consistently carried through it would have been necessary to develop rules of "private international law" in order to decide in doubtful cases, where a Roman and a peregrine or peregrines of different states were concerned, which system was to be applied. Such rules did not come into existence, partly perhaps because of the multitude of states whose systems the Roman court would have had to notice, but more especially because, as the Roman power grew, so the "foreigners" concerned were more and more generally, in fact, subjects of Rome, with the niceties of whose law the Roman magistrate might get a little impatient. In any case there did grow up, through the edicts of the praetor peregrinus and the provincial governors, a system which was neither the Roman ius civile nor a code of "private international law", but a general system of rules governing relations between free men as such, without reference to their nationality. Much of this system of law, seeing that it was based on the edicts of Roman magistracies, was Roman in origin, but it was Roman law stripped to a great extent of its formal elements, and influenced by other, especially Greek, ideas. Thus the Roman contract of stipulation was one of the institutions extended in this way to foreigners, i.e. a foreigner can be bound and entitled under it, and it is not difficult to see why, for although the stipulation is what we call a formal contract, the forms required are the simplest imaginable, and the contract is useful for all manner of purposes. Mancipation, on the other hand, with its elaborate ceremony, involving the use of scales and copper and the speaking of set words, remains exclusively a transaction of the ius civile. It must also be noticed that the rules of which we are speaking refer almost exclusively to transactions inter vivos; matters of family law and of succession remain under the personal law of each particular man.
That the phrase ius gentium was ever applied to these rules developed in the peregrine and provincial edicts cannot be shown, but it is clear that they were of great importance in leading up to the conception of the ius gentium, for, once established, they in their turn influenced the development of the law as applied between citizens, especially in the direction of making it less formal, and thus there came into existence the ius gentium, in its practical sense, i.e. "that part of the law which we apply both to ourselves and to foreigners". In this sense there is a great deal of law which is iuris gentium, e.g. not only the stipulation among contracts, but all the informal contracts, both "real" and "consensual" (the consensual at least being probably importations from the rules developed for foreigners), and much of the law of delict, which is extended from the civil law to apply where foreigners are concerned by the "fiction" that the foreigner is a citizen.
In the sources this "practical" sense of the phrase ius gentium is not always clear, because the Roman writers themselves do not distinguish it from a rather different sense which is not practical but derived from Greek philosophical theories. Aristotle, speaking of law in general, had divided in into two parts, that which was "natural" and that which was man-made, and he asserted that natural law was the same everywhere and had equal validity everywhere; as well as being "natural" it was "common". This idea became a commonplace, especially among the Stoics, with whose ideal of a "life according to Nature" it of course fitted admirably. Cicero repeats lofty sentiments about the law of Nature in a similar strain; he does not, any more than the Greeks, get beyond elementary moral rules when he gives instances of the precepts of this law, but it is clear that for him, as for Aristotle, the universality of a principle is a proof of its naturalness and hence of its validity, for the law of Nature is no mere ideal, it is a binding law and no enactment of the people or senatus-consult can prevail against it. The argument, though not put in these words, is obvious: if all races of manking acknowledge a practice it must be because it has been taught them by their universal mother, Nature. Cicero thus identifies the law of Nature with the ius gentium in the sense of law common to all peoples, and draws the inference that what is part of the ius gentium should also be part of the ius civile, i.e. of the law of each particular state, although what is ius civile is not necessarily ius gentium, for, as in Aristotle's view, there are matters on which Nature is indifferent and each community can lay down rules for itself. This theoretical view of the ius gentium as law common to all mankind became current coin among the jurists. Gaius begins his Institutes almost in the words of Aristotle, "All peoples who are governed by laws and customs apply partly their own law, partly law which is common to all mankind; for the law which each people has made for itself is peculiar to that people and is called its ius civile, the special law of the state; but that which natural reason has appointed for all men is in force equally among all peoples, and is called ius gentium, being the law applied by all races. Thus the Roman people applies partly its own law, partly that common to all men".
The difference between this "theoretical" meaning and the "practical" meaning of which we spoke above, is best seen when we consider the correlative term to ius gentium. In each case it is ius civile, but in translating this phrase into English we have to differentiate. Where the "practical" meaning is in question, we say "civil law", meaning "Roman law", e.g. the answer to the question whether mancipatio is an institution of the ius gentium is "No; it is an institution of the civil law". But where the theoretical meaning is in question, as in the passage from Gaius above, we have to refer to the particular state in question, e.g. if we ask, "Is the rule that a husband or son must authorise a woman's contract part of the ius gentium?" the answer would have to be: "No; it is a rule of Bithynian civil law". Justinian makes this quite clear. "If", he says, "a man wishes to call the laws of Solon or Draco Athenian civil law, he will not be wrong".
It is true that this distinction is not made by the Romans themselves –they did not in fact succeed in distinguishing morals from law in theory– but it is there all the same and must be grasped if we are to understand the different senses in which an institution can be said to be part of the ius gentium. The sense in which the stipulation, for instance, can be so classified has been explained; it is part of the ius gentium because an Athenian or a Gaul or a Junian Latin, who has no state, may be bound or entitled under it. But when the Romans say that slavery and manumission or the right of capturing things in war (occupatio bellica) is part of the ius gentium they mean something different. They mean that these institutions are common to all systems of law which they know, not that they will be recognised in a Roman court. A person who alleges that he has been manumitted by a foreigner cannot claim to be free by Roman law; whether he is free or not will depend on the law of his manumitter's state. It is true that all states know manumission, but the rules on the subject differ greatly from state to state; whereas when a stipulation is mentioned the Roman institution of that name is meant, and any rules there may be in the systems of other states with regard to some similar contract do not matter in the least. It is this latter sort of ius gentium alone which really concerns the practical lawyer; the rest is philosophical ornament.
As appears from what has already been said the law of Nature is only another name for the (theoretical) ius gentium. Not only does Cicero identify them, but the lawyers generally use the two phrases indiscriminately. Only one refinement which occasionally appears needs mention. If there was one institution which was really common to all peoples of antiquity it was slavery, which consequently is always reckoned as iuris gentium. According to Aristotle it was also natural, for some men were slaves by nature, but other Greek philosophers had different views; man was by nature free, and we thus find slavery defined occasionally as an institution of the ius gentium contrary to Nature and resulting from war. But this is the only case in which a discrepancy between the two systems can be found. An identification, ascribed to Ulpian, of the law of Nature with the instincts which men share with animals is unfortunately given prominence by appearing in Justinian's Institutes, but it is an isolated opinion in legal literature and was never made the basis of any consistent theory.
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Source:
Historical introduction to the study of Roman law, H. F. Jolowicz, pages 100 - 105.
