In theory the Emperor of the Germans remained for hundreds of years to come the master of the world, but in practice he was not even master at home, as the German Princes step by step succeeded in establishing their independence. And although theoretically the world was well looked after by the Emperor as its temporal and the Pope as its spiritual head, there were constantly treachery, quarrelling, and fighting going on. War practice was the most cruel possible. It is true that the Pope and the Bishops succeeded sometimes in mitigating such practice, but as a rule there was no influence of the Christian teaching visible.
The Fifteenth and Sixteenth Centuries.
§ 42. The necessity for a Law of Nations did not arise until a multitude of States absolutely independent of one another had successfully established themselves. The process of development, starting from the Treaty of Verdun of 843, reached that climax with the reign of Frederic III., Emperor of the Germans from 1440 to 1493. He was the last of the emperors crowned in Rome by the hands of the Popes. At that time Europe was, in fact, divided up into a great number of independent States, and thenceforth a law was needed to deal with the international relations of these Sovereign States. Seven factors of importance prepared the ground for the growth of principles of a future International Law.
(1) There were, first, the Civilians and the Canonists. Roman Law was in the beginning of the twelfth century brought back to the West through Irnerius, who taught this law at Bologna. He and the other glossatores and post-glossatores considered Roman Law the ratio scripta, the law par excellence. These Civilians maintained that Roman Law was the law of the civilised world ipso facto through the emperors of the Germans being the successors of the emperors of Rome. Their commentaries to the Corpus Juris Civilis touch upon many questions of the future International Law which they discuss from the basis of Roman Law.
The Canonists, on the other hand, whose influence was unshaken till the time of the Reformation, treated from a moral and ecclesiastical point of view many questions of the future International Law concerning war.[35]
[35] See Holland, Studies, pp. 40-58; Walker, History, I. pp. 204-212.
(2) There were, secondly, collections of Maritime Law of great importance which made their appearance in connection with international trade. From the eighth century the world trade, which had totally disappeared in consequence of the downfall of the Roman Empire and the destruction of the old civilisation during the period of the Migration of the Peoples, began slowly to develop again. The sea trade specially flourished and fostered the growth of rules and customs of Maritime Law, which were collected into codes and gained some kind of international recognition. The more important of these collections are the following: The Consolato del Mare, a private collection made at Barcelona in Spain in the middle of the fourteenth century; the Laws of Oléron, a collection, made in the twelfth century, of decisions given by the maritime court of Oléron in France; the Rhodian Laws, a very old collection of maritime laws which probably was put together between the sixth and the eighth centuries;[36] the Tabula Amalfitana, the maritime laws of the town of Amalfi in Italy, which date at latest from the tenth century; the Leges Wisbuenses, a collection of maritime laws of Wisby on the island of Gothland, in Sweden, dating from the fourteenth century.
[36] See Ashburner, "The Rhodian Sea Law" (1909), Introduction, p. cxii.
The growth of international trade caused also the rise of the controversy regarding the freedom of the high seas (see below, § [248]), which indirectly influenced the growth of an International Law (see below, §§ [248]-250).
(3) A third factor was the numerous leagues of trading towns for the protection of their trade and trading citizens. The most celebrated of these leagues is the Hanseatic, formed in the thirteenth century. These leagues stipulated for arbitration on controversies between their member towns. They acquired trading privileges in foreign States. They even waged war, when necessary, for the protection of their interests.