INTRODUCTION FOUNDATION AND DEVELOPMENT OF THE LAW OF NATIONS

CHAPTER I FOUNDATION OF THE LAW OF NATIONS

I THE LAW OF NATIONS AS LAW

Hall, pp. 14-16—Maine, pp. 50-53—Lawrence, §§ 1-3, and Essays, pp. 1-36—Phillimore, I. §§ 1-12—Twiss, I. §§ 104-5—Taylor, § 2—Moore, I. §§ 1-2—Westlake, I. pp. 1-13—Walker, History, I. §§ 1-8—Halleck, I. pp. 46-55—Ullmann, §§ 2-4—Heffter, §§ 1-5—Holtzendorff in Holtzendorff, I. pp. 19-26—Nys, I. pp. 133-43—Rivier, I. § 1—Bonfils, Nos. 26-31—Pradier-Fodéré, I. Nos. 1-24—Mérignhac, I. pp. 5-28—Martens, I. §§ 1-5—Fiore, I. Nos. 186-208, and Code, Nos. 1-26—Higgins, "The Binding Force of International Law" (1910)—Pollock in The Law Quarterly Review, XVIII. (1902), pp. 418-428—Scott in A.J. I. (1907), pp. 831-865—Willoughby and Root in A.J. II. (1908), pp. 357-365 and 451-457.

§ 1. Law of Nations or International Law (Droit des gens, Völkerrecht) is the name for the body of customary and conventional rules which are considered legally[1] binding by civilised States in their intercourse with each other. Such part of these rules as is binding upon all the civilised States without exception is called universal International Law,[2] in contradistinction to particular International Law, which is binding on two or a few States only. But it is also necessary to distinguish general International Law. This name must be given to the body of such rules as are binding upon a great many States, including leading Powers. General International Law, as, for instance, the Declaration of Paris of 1856, has a tendency to become universal International Law.

International Law in the meaning of the term as used in modern times did not exist during antiquity and the first part of the Middle Ages. It is in its origin essentially a product of Christian civilisation, and began gradually to grow from the second half of the Middle Ages. But it owes its existence as a systematised body of rules to the Dutch jurist and statesman Hugo Grotius, whose work, "De Jure Belli ac Pacis libri III.," appeared in 1625 and became the foundation of all later development.

The Law of Nations is a law for the intercourse of States with one another, not a law for individuals. As, however, there cannot be a sovereign authority above the several sovereign States, the Law of Nations is a law between, not above, the several States, and is, therefore, since Bentham, also called "International Law."

Since the distinction of Bentham between International Law public and private has been generally accepted, it is necessary to emphasise that only the so-called public International Law, which is identical with the Law of Nations, is International Law, whereas the so-called private International Law is not. The latter concerns such matters as fall at the same time under the jurisdiction of two or more different States. And as the Municipal Laws of different States are frequently in conflict with each other respecting such matters, jurists belonging to different countries endeavour to find a body of principles according to which such conflicts can be avoided.

§ 2. Almost from the beginning of the science of the Law of Nations the question has been discussed whether the rules of International Law are legally binding. Hobbes[3] already and Pufendorf[4] had answered the question in the negative. And during the nineteenth century Austin[5] and his followers take up the same attitude. They define law as a body of rules for human conduct set and enforced by a sovereign political authority. If indeed this definition of law be correct, the Law of Nations cannot be called law. For International Law is a body of rules governing the relations of Sovereign States between one another. And there is not and cannot be a sovereign political authority above the Sovereign States which could enforce such rules. However, this definition of law is not correct. It covers only the written or statute law within a State, that part of the Municipal Law which is expressly made by statutes of Parliament in a constitutional State or by some other sovereign authority in a non-constitutional State. It does not cover that part of Municipal Law which is termed unwritten or customary law. There is, in fact, no community and no State in the world which could exist with written law only. Everywhere there is customary law in existence besides the written law. This customary law was never expressly enacted by any law-giving body, or it would not be merely customary law. Those who define law as rules set and enforced by a sovereign political authority do not deny the existence of customary law. But they maintain that the customary law has the character of law only through the indirect recognition on the part of the State which is to be found in the fact that courts of justice apply the customary in the same way as the written law, and that the State does not prevent them from doing so. This is, however, nothing else than a fiction. Courts of justice having no law-giving power could not recognise unwritten rules as law if these rules were not law before that recognition, and States recognise unwritten rules as law only because courts of justice do so.

§ 3. For the purpose of finding a correct definition of law it is indispensable to compare morality and law with each other, for both lay down rules, and to a great extent the same rules, for human conduct. Now the characteristic of rules of morality is that they apply to conscience, and to conscience only. An act loses all value before the tribunal of morality, if it was not done out of free will and conscientiousness, but was enforced by some external power or was done out of some consideration which lies without the boundaries of conscience. Thus, a man who gives money to the hospitals in order that his name shall come before the public does not act morally, and his deed is not a moral one, though it appears to be one outwardly. On the other hand, the characteristic of rules of law is that they shall eventually be enforced by external power.[6] Rules of law apply, of course, to conscience quite as much as rules of morality. But the latter require to be enforced by the internal power of conscience only, whereas the former require to be enforced by some external power. When, to give an illustrative example, morality commands you to pay your debts, it hopes that your conscience will make you pay them. On the other hand, if the law gives the same command, it hopes that, if the conscience has not sufficient power to make you pay your debts, the fact that, if you will not pay, the bailiff will come into your house, will do so.

§ 4. If these are the characteristic signs of morality and of law, we are justified in stating the principle: A rule is a rule of morality, if by common consent of the community it applies to conscience and to conscience only; whereas, on the other hand, a rule is a rule of law, if by common consent of the community it shall eventually be enforced by external power. Without some kind both of morality and law, no community has ever existed or could possibly exist. But there need not be, at least not among primitive communities, a law-giving authority within a community. Just as the rules of morality are growing through the influence of many different factors, so the law can grow without being expressly laid down and set by a law-giving authority. Wherever we have an opportunity of observing a primitive community, we find that some of its rules for human conduct apply to conscience only, whereas others shall by common consent of the community be enforced; the former are rules of morality only, whereas the latter are rules of law. For the existence of law neither a law-giving authority nor courts of justice are essential. Whenever a question of law arises in a primitive community, it is the community itself and not a court which decides it. Of course, when a community is growing out of the primitive condition of its existence and becomes gradually so enlarged that it turns into a State in the sense proper of the term, the necessities of life and altered circumstances of existence do not allow the community itself any longer to do anything and everything. And the law can now no longer be left entirely in the hands of the different factors which make it grow gradually from case to case. A law-giving authority is now just as much wanted as a governing authority. It is for this reason that we find in every State a Legislature, which makes laws, and courts of justice, which administer them.

However, if we ask whence does the power of the legislature to make laws come, there is no other answer than this: From the common consent of the community. Thus, in Great Britain, Parliament is the law-making body by common consent. An Act of Parliament is law, because the common consent of Great Britain is behind it. That Parliament has law-making authority is law itself, but unwritten and customary law. Thus the very important fact comes to light that all statute or written law is based on unwritten law in so far as the power of Parliament to make Statute Law is given to Parliament by unwritten law. It is the common consent of the British people that Parliament shall have the power of making rules which shall be enforced by external power. But besides the statute laws made by Parliament there exist and are constantly growing other laws, unwritten or customary, which are day by day recognised through courts of justice.

§ 5. On the basis of the results of these previous investigations we are now able to give a definition of law. We may say that law is a body of rules for human conduct within a community which by common consent of this community shall be enforced by external power.

The essential conditions of the existence of law are, therefore, threefold. There must, first, be a community. There must, secondly, be a body of rules for human conduct within that community. And there must, thirdly, be a common consent of that community that these rules shall be enforced by external power. It is not an essential condition either that such rules of conduct must be written rules, or that there should be a law-making authority or a law-administering court within the community concerned. And it is evident that, if we find this definition of law correct, and accept these three essential conditions of law, the existence of law is not limited to the State community only, but is to be found everywhere where there is a community. The best example of the existence of law outside the State is the law of the Roman Catholic Church, the so-called Canon Law. This Church is an organised community whose members are dispersed over the whole surface of the earth. They consider themselves bound by the rules of the Canon Law, although there is no sovereign political authority that sets and enforces those rules, the Pope and the bishops and priests being a religious authority only. But there is an external power through which the rules of the Canon Law are enforced—namely, the punishments of the Canon Law, such as excommunication, refusal of sacraments, and the like. And the rules of the Canon Law are in this way enforced by common consent of the whole Roman Catholic community.

§ 6. But it must be emphasised that, if there is law to be found in every community, law in this meaning must not be identified with the law of States, the so-called Municipal Law,[7] just as the conception of State must not be identified with the conception of community. The conception of community is a wider one than the conception of State. A State is a community, but not every community is a State. Likewise the conception of law pure and simple is a wider one than that of Municipal Law. Municipal Law is law, but not every law is Municipal Law, as, for instance, the Canon Law is not. Municipal Law is a narrower conception than law pure and simple. The body of rules which is called the Law of Nations might, therefore, be law in the strict sense of the term, although it might not possess the characteristics of Municipal Law. To make sure whether the Law of Nations is or is not law, we have to inquire whether the three essential conditions of the existence of law are to be found in the Law of Nations.

§ 7. As the first condition is the existence of a community, the question arises, whether an international community exists whose law could be the Law of Nations. Before this question can be answered, the conception of community must be defined. A community may be said to be the body of a number of individuals more or less bound together through such common interests as create a constant and manifold intercourse between the single individuals. This definition of community covers not only a community of individual men, but also a community of individual communities such as individual States. A Confederation of States is a community of States. But is there a universal international community of all individual States in existence? This question is decidedly to be answered in the affirmative as far as the States of the civilised world are concerned. Innumerable are the interests which knit all the individual civilised States together and which create constant intercourse between these States as well as between their subjects. As the civilised States are, with only a few exceptions, Christian States, there are already religious ideas which wind a band around them. There are, further, science and art, which are by their nature to a great extent international, and which create a constant exchange of ideas and opinions between the subjects of the several States. Of the greatest importance are, however, agriculture, industry, and trade. It is totally impossible even for the largest empire to produce everything its subjects want. Therefore, the productions of agriculture and industry must be exchanged by the several States, and it is for this reason that international trade is an unequalled factor for the welfare of every civilised State. Even in antiquity, when every State tried to be a world in itself, States did not and could not exist without some sort of international trade. It is international trade which has created navigation on the high seas and on the rivers flowing through different States. It is, again, international trade which has called into existence the nets of railways which cover the continents, the international postal and telegraphic arrangements, and the Transatlantic telegraphic cables.[8]

The manifold interests which knit all the civilised States together and create a constant intercourse between one another, have long since brought about the necessity that these States should have one or more official representatives living abroad. Thus we find everywhere foreign envoys and consuls. They are the agents who make possible the current stream of transactions between the Governments of the different States. A number of International Offices, International Bureaux, International Commissions have been permanently appointed for the administration of international business, a permanent Court of Arbitration has been, and an International Prize Court will soon be, established at the Hague. And from time to time special international conferences and congresses of delegates of the different States are convoked for discussing and settling matters international. Though the individual States are sovereign and independent of each other, though there is no international Government above the national ones, though there is no central political authority to which the different States are subjected, yet there is something mightier than all the powerful separating factors: namely, the common interests. And these common interests and the necessary intercourse which serves these interests, unite the separate States into an indivisible community. For many hundreds of years this community has been called "Family of Nations" or "Society of Nations."

§ 8. Thus the first essential condition for the existence of law is a reality. The single States make altogether a body of States, a community of individual States. But the second condition cannot be denied either. For hundreds of years more and more rules have grown up for the conduct of the States between each other. These rules are to a great extent customary rules. But side by side with these customary and unwritten rules more and more written rules are daily created by international agreements, such as the Declaration of Paris of 1856, the Hague Rules concerning land warfare of 1899 and 1907, and the like. The so-called Law of Nations is nothing else than a body of customary and conventional rules regulating the conduct of the individual States with each other. Just as out of tribal communities which were in no way connected with each other arose the State, so the Family of Nations arose out of the different States which were in no way connected with each other. But whereas the State is a settled institution, firmly established and completely organised, the Family of Nations is still in the beginning of its development. A settled institution and firmly established it certainly is, but it entirely lacks at present any organisation whatever. Such an organisation is, however, gradually growing into existence before our eyes. The permanent Court of Arbitration created by the First Hague Peace Conference, and the International Prize Court proposed by the Second Hague Peace Conference, are the first small traces of a future organisation. The next step forward will be that the Hague Peace Conferences will meet automatically within certain periods of time, without being summoned by one of the Powers. A second step forward will be the agreement on the part of the Powers upon fixed rules of procedure for the future Hague Peace Conferences. As soon as these two steps forward are really made, the nucleus of an organisation of the Family of Nations will be in existence, and out of this nucleus will grow in time a more powerful organisation, the ultimate characteristic features of which cannot at present be foreseen.[9]

§ 9. But how do matters stand concerning the third essential condition for the existence of law? Is there a common consent of the community of States that the rules of international conduct shall be enforced by external power? There cannot be the slightest doubt that this question must be affirmatively answered, although there is no central authority to enforce those rules. The heads of the civilised States, their Governments, their Parliaments, and public opinion of the whole of civilised humanity, agree and consent that the body of rules of international conduct which is called the Law of Nations shall be enforced by external power, in contradistinction to rules of international morality and courtesy, which are left to the consideration of the conscience of nations. And in the necessary absence of a central authority for the enforcement of the rules of the Law of Nations, the States have to take the law into their own hands. Self-help and intervention on the part of other States which sympathise with the wronged one are the means by which the rules of the Law of Nations can be[10] and actually are enforced. It is true that these means have many disadvantages, but they are means which have the character of external power. Compared with Municipal Law and the means at disposal for its enforcement, the Law of Nations is certainly the weaker of the two. A law is the stronger, the more guarantees are given that it can and will be enforced. Thus, the law of a State which is governed by an uncorrupt Government and the courts of which are not venal is stronger than the law of a State which has a corrupt Government and venal judges. It is inevitable that the Law of Nations must be a weaker law than Municipal Law, as there is not and cannot be an international Government above the national ones which could enforce the rules of International Law in the same way as a national Government enforces the rules of its Municipal Law. But a weak law is nevertheless still law, and the Law of Nations is by no means so weak a law as it sometimes seems to be.[11]

§ 10. The fact is that theorists only are divided concerning the character of the Law of Nations as real law. In practice International Law is constantly recognised as law. The Governments and Parliaments of the different States are of opinion that they are legally, not morally only, bound by the Law of Nations, although they cannot be forced to go before a court in case they are accused of having violated it. Likewise, public opinion of all civilised States considers every State legally bound to comply with the rules of the Law of Nations, not taking notice of the opinion of those theorists who maintain that the Law of Nations does not bear the character of real law. And the several States not only recognise the rules of International Law as legally binding in innumerable treaties, but emphasise every day the fact that there is a law between themselves. They moreover recognise this law by their Municipal Laws ordering their officials, their civil and criminal courts, and their subjects to take up such an attitude as is in conformity with the duties imposed upon their Sovereign by the Law of Nations. If a violation of the Law of Nations occurs on the part of an individual State, public opinion of the civilised world, as well as the Governments of other States, stigmatise such violation as a violation of law pure and simple. And countless treaties concerning trade, navigation, post, telegraph, copyright, extradition, and many other objects exist between civilised States, which treaties, resting entirely on the existence of a law between the States, presuppose such a law, and contribute by their very existence to its development and growth.

Violations of this law are certainly frequent. But the offenders always try to prove that their acts do not contain a violation, and that they have a right to act as they do according to the Law of Nations, or at least that no rule of the Law of Nations is against their acts. Has a State ever confessed that it was going to break the Law of Nations or that it ever did so? The fact is that States, in breaking the Law of Nations, never deny its existence, but recognise its existence through the endeavour to interpret the Law of Nations in a way favourable to their act. And there is an ever-growing tendency to bring disputed questions of International Law as well as international differences in general before international courts. The permanent Court of Arbitration at the Hague established in 1899, and the International Prize Court proposed at the Hague according to a convention of 1907, are the first promising fruits of this tendency.

II BASIS OF THE LAW OF NATIONS

§ 11. If law is, as defined above (§ 5), a body of rules for human conduct within a community which by common consent of this community shall be enforced through external power, common consent is the basis of all law. What, now, does the term "common consent" mean? If it meant that all the individuals who are members of a community must at every moment of their existence expressly consent to every point of law, such common consent would never be a fact. The individuals, who are the members of a community, are successively born into it, grow into it together with the growth of their intellect during adolescence, and die away successively to make room for others. The community remains unaltered, although a constant change takes place in its members. "Common consent" can therefore only mean the express or tacit consent of such an overwhelming majority of the members that those who dissent are of no importance whatever, and disappear totally from the view of one who looks for the will of the community as an entity in contradistinction to the wills of its single members. The question as to whether there be such a common consent in a special case, is not a question of theory, but of fact only. It is a matter of observation and appreciation, and not of logical and mathematical decision, just as is the well-known question, how many grains make a heap? Those legal rules which come down from ancestors to their descendants remain law so long only as they are supported by common consent of these descendants. New rules can only become law if they find common consent on the part of those who constitute the community at the time. It is for that reason that custom is at the background of all law, whether written or unwritten.

§ 12. What has been stated with regard to law pure and simple applies also to the Law of Nations. However, the community for which this Law of Nations is authoritative consists not of individual human beings, but of individual States. And whereas in communities consisting of individual human beings there is a constant and gradual change of the members through birth, death, emigration, and immigration, the Family of Nations is a community within which no such constant change takes place, although now and then a member disappears and a new member steps in. The members of the Family of Nations are therefore not born into that community and they do not grow into it. New members are simply received into it through express or tacit recognition. It is therefore necessary to scrutinise more closely the common consent of the States which is the basis of the Law of Nations.

The customary rules of this law have grown up by common consent of the States—that is, the different States have acted in such a manner as includes their tacit consent to these rules. As far as the process of the growth of a usage and its turning into a custom can be traced back, customary rules of the Law of Nations came into existence in the following way. The intercourse of States with each other necessitated some rules of international conduct. Single usages, therefore, gradually grew up, the different States acting in the same or in a similar way when an occasion arose. As some rules of international conduct were from the end of the Middle Ages urgently wanted, the theory of the Law of Nations prepared the ground for their growth by constructing certain rules on the basis of religious, moral, rational, and historical reflections. Hugo Grotius's work, "De Jure Belli ac Pacis libri III." (1625), offered a systematised body of rules, which recommended themselves so much to the needs and wants of the time that they became the basis of the development following. Without the conviction of the Governments and of public opinion of the civilised States that there ought to be legally binding rules for international conduct, on the one hand, and, on the other hand, without the pressure exercised upon the States by their interests and the necessity for the growth of such rules, the latter would never have grown up. When afterwards, especially in the nineteenth century, it became apparent that customs and usages alone were not sufficient or not sufficiently clear, new rules were created through law-making treaties being concluded which laid down rules for future international conduct. Thus conventional rules gradually grew up side by side with customary rules.

New States which came into existence and were through express or tacit recognition admitted into the Family of Nations thereby consented to the body of rules for international conduct in force at the time of their admittance. It is therefore not necessary to prove for every single rule of International Law that every single member of the Family of Nations consented to it. No single State can say on its admittance into the Family of Nations that it desires to be subjected to such and such a rule of International Law, and not to others. The admittance includes the duty to submit to all the rules in force, with the sole exception of those which, such as the rules of the Geneva Convention for instance, are specially stipulated for such States only as have concluded, or later on acceded to, a certain international treaty creating the rules concerned.

On the other hand, no State which is a member of the Family of Nations can at some time or another declare that it will in future no longer submit to a certain recognised rule of the Law of Nations. The body of the rules of this law can be altered by common consent only, not by a unilateral declaration on the part of one State. This applies not only to customary rules, but also to such conventional rules as have been called into existence through a law-making treaty for the purpose of creating a permanent mode of future international conduct without a right of the signatory powers to give notice of withdrawal. It would, for instance, be a violation of International Law on the part of a signatory Power of the Declaration of Paris of 1856 to declare that it would cease to be a party. But it must be emphasised that this does not apply to such conventional rules as are stipulated by a law-making treaty which expressly reserves the right to the signatory Powers to give notice.

§ 13. Since the Law of Nations is based on the common consent of individual States, and not of individual human beings, States solely and exclusively are the subjects of International Law. This means that the Law of Nations is a law for the international conduct of States, and not of their citizens. Subjects of the rights and duties arising from the Law of Nations are States solely and exclusively. An individual human being, such as a king or an ambassador for example, is never directly a subject of International Law. Therefore, all rights which might necessarily have to be granted to an individual human being according to the Law of Nations are not international rights, but rights granted by Municipal Law in accordance with a duty imposed upon the respective State by International Law. Likewise, all duties which might necessarily have to be imposed upon individual human beings according to the Law of Nations are not international duties, but duties imposed by Municipal Law in accordance with a right granted to or a duty imposed upon the respective State by International Law. Thus the privileges of an ambassador are granted to him by the Municipal Law of the State to which he is accredited, but such State has the duty to grant these privileges according to International Law. Thus, further, the duties incumbent upon officials and subjects of neutral States in time of war are imposed upon them by the Municipal Law of their home States, but these States have, according to International Law, the duty of imposing the respective duties upon their officials and citizens.[12]

§ 14. Since the Law of Nations is based on the common consent of States as sovereign communities, the member States of the Family of Nations are equal to each other as subjects of International Law. States are by their nature certainly not equal as regards power, extent, constitution, and the like. But as members of the community of nations they are equals, whatever differences between them may otherwise exist. This is a consequence of their sovereignty and of the fact that the Law of Nations is a law between, not above, the States.[13]

III SOURCES OF THE LAW OF NATIONS

Hall, pp. 5-14—Maine, pp. 1-25—Lawrence, §§ 61-66—Phillimore, I. §§ 17-33—Twiss, I. §§ 82-103—Taylor, §§ 30-36—Westlake, I. pp. 14-19—Wheaton, § 15—Halleck, I. pp. 55-64—Ullmann, §§ 8-9—Heffter, § 3—Holtzendorff in Holtzendorff, I. pp. 79-158—Rivier, I. § 2—Nys, I. pp. 144-165—Bonfils, Nos. 45-63—Despagnet, Nos. 58-63—Pradier-Fodéré, I. Nos. 24-35—Mérignhac, I. pp. 79-113—Martens, I. § 43—Fiore, I. Nos. 224-238—Calvo, I. §§ 27-38—Bergbohm, "Staatsverträge und Gesetze als Quellen des Völkerrechts" (1877)—Jellinek, "Die rechtliche Natur der Staatsverträge" (1880)—Cavaglieri, "La consuetudine giuridica internazionale" (1907).

§ 15. The different writers on the Law of Nations disagree widely with regard to kinds and numbers of sources of this law. The fact is that the term "source of law" is made use of in different meanings by the different writers on International Law, as on law in general. It seems to me that most writers confound the conception of "source" with that of "cause," and through this mistake come to a standpoint from which certain factors which influence the growth of International Law appear as sources of rules of the Law of Nations. This mistake can be avoided by going back to the meaning of the term "source" in general. Source means a spring or well, and has to be defined as the rising from the ground of a stream of water. When we see a stream of water and want to know whence it comes, we follow the stream upwards until we come to the spot where it rises naturally from the ground. On that spot, we say, is the source of the stream of water. We know very well that this source is not the cause of the existence of the stream of water. Source signifies only the natural rising of water from a certain spot of the ground, whatever natural causes there may be for that rising. If we apply the conception of source in this meaning to the term "source of law," the confusion of source with cause cannot arise. Just as we see streams of water running over the surface of the earth, so we see, as it were, streams of rules running over the area of law. And if we want to know whence these rules come, we have to follow these streams upwards until we come to their beginning. Where we find that such rules rise into existence, there is the source of them. Of course, rules of law do not rise from a spot on the ground as water does; they rise from facts in the historical development of a community. Thus in Great Britain a good many rules of law rise every year from Acts of Parliament. "Source of Law" is therefore the name for an historical fact out of which rules of conduct rise into existence and legal force.

§ 16. As the basis of the Law of Nations is the common consent of the member States of the Family of Nations, it is evident that there must exist, and can only exist, as many sources of International Law as there are facts through which such common consent can possibly come into existence. Of such facts there are only two. A State, just as an individual, may give its consent either directly by an express declaration or tacitly by conduct which it would not follow in case it did not consent. The sources of International Law are therefore twofold—namely: (1) express consent, which is given when States conclude a treaty stipulating certain rules for the future international conduct of the parties; (2) tacit consent, which is given through States having adopted the custom of submitting to certain rules of international conduct. Treaties and custom are, therefore, exclusively the sources of the Law of Nations.

§ 17. Custom is the older and the original source of International Law in particular as well as of law in general. Custom must not be confounded with usage. In everyday life and language both terms are used synonymously, but in the language of the jurist they have two distinctly different meanings. Jurists speak of a custom, when a clear and continuous habit of doing certain actions has grown up under the ægis of the conviction that these actions are legally necessary or legally right. On the other hand, jurists speak of a usage, when a habit of doing certain actions has grown up without there being the conviction of their legal character. Thus the term "custom" is in juristic language a narrower conception than the term "usage," as a given course of conduct may be usual without being customary. Certain conduct of States concerning their international relations may therefore be usual without being the outcome of customary International Law.

As usages have a tendency to become custom, the question presents itself, at what time a usage turns into a custom. This question is one of fact, not of theory. All that theory can point out is this: Wherever and as soon as a frequently adopted international conduct of States is considered legally necessary or legally right, the rule which may be abstracted from such conduct, is a rule of customary International Law.

§ 18. Treaties are the second source of International Law, and a source which has of late become of the greatest importance. As treaties may be concluded for innumerable purposes,[14] it is necessary to emphasise that such treaties only are a source of International Law as either stipulate new rules for future international conduct or confirm, define, or abolish existing customary or conventional rules. Such treaties must be called law-making treaties. Since the Family of Nations is not a State-like community, there is no central authority which could make law for it in a similar way as Parliaments make law by statutes within the States. The only way in which International Law can be made by a deliberate act, in contradistinction to custom, is that the members of the Family of Nations conclude treaties in which certain rules for their future conduct are stipulated. Of course, such law-making treaties create law for the contracting parties solely. Their law is universal International Law then only, when all the members of the Family of Nations are parties to them. Many law-making treaties are concluded by a few States only, so that the law which they create is particular International Law. On the other hand, there have been many law-making treaties concluded which contain general International Law, because the majority of States, including leading Powers, are parties to them. General International Law has a tendency to become universal because such States as hitherto did not consent to it will in future either expressly give their consent or recognise the respective rules tacitly through custom.[15] But it must be emphasised that, whereas custom is the original source of International Law, treaties are a source the power of which derives from custom. For the fact that treaties can stipulate rules of international conduct at all is based on the customary rule of the Law of Nations, that treaties are binding upon the contracting parties.[16]