Under the direction of Tribonian, the Corpus Iurus Civilis [Body of Civil Law] was issued in three parts, in Latin, at the order of the Emperor Justinian. The Codex Justinianus (529) compiled all of the extant (in Justinian's time) imperial constitutiones from the time of Hadrian. It used both the Codex Theodosianus and private collections such as the Codex Gregorianus and Codex Hermogenianus. The Digest, or Pandects, was issued in 533, and was a greater achievement: it compiled the writings of the great Roman jurists such as Ulpian along with current edicts. It constituted both the current law of the time, and a turning point in Roman Law: from then on the sometimes contradictory case law of the past was subsumed into an ordered legal system. The Institutes was intended as sort of legal textbook for law schools and included extracts from the two major works. Later, Justinian issued a number of other laws, mostly in Greek, which were called Novels.

Book I. Of Persons

I. Justice and Law. JUSTICE is the constant and perpetual wish to render every one his due.
1. Jurisprudence is the knowledge of things divine and human; the science of the just and the unjust.
2. Having explained these general terms, we think we shall commence our exposition of the law of the Roman people most advantageously, if we pursue at first a plain and easy path, and then proceed to explain particular details with the utmost care and exactness. For, if at the outset we overload the mind of the student, while yet new to the subject and unable to bear much, with a multitude and variety of topics, one of two things will happen---we shall either cause him wholly to abandon his studies, or, after great toil, and often after great distrust to himself (the most frequent stumbling block in the way of youth), we shall at last conduct him to the point, to which, if he had been led by an easier road, he might, without great labor, and without any distrust of his own powers, have been sooner conducted.
3. The maxims of law are these: to live honesty, to hurt no one, to give every one his due.
4. The study of law is divided into two branches; that of public and that of private law. Public law regards the government of the Roman empire; private law, the interest of the individuals. We are now to treat of the latter, which is composed of three elements, and consists of precepts belonging to the natural law, to the law of nations, and to the civil law.

II. Natural, Common, and Civil Law.
The law of nature is that law which nature teaches to all animals. For this law does not belong exclusively to the human race, but belongs to all animals, whether of the earth, the air, or the water. Hence comes the union of the male and female, which we term matrimony; hence the procreation and bringing up of children. We see, indeed, that all the other animals besides men are considered as having knowledge of this law.
1. Civil law is thus distinguished from the law of nations. Every community governed by laws and customs uses partly its own law, partly laws common to all mankind. The law which a people makes for its own government belongs exclusively to that state and is called the civil law, as being the law of the particular state. But the law which natural reason appoints for all mankind obtains equally among all nations, because all nations make use of it. The people of Rome, then, are governed partly by their own laws, and partly by the laws which are common to all mankind. We will take notice of this distinction as occasion may arise.
2. Civil law takes its name from the state which it governs, as, for instance, from Athens; for it would be very proper to speak of the laws of Solon or Draco as the civil law of Athens. And thus the law which the Roman people make use of is called the civil law of the Romans, or that of the Quirites; for the Romans are called Quirites from Quirinum. But whenever we speak of civil law, without adding the name of any state, we mean our own law; just as the Greeks, when "the poet" is spoken of without any name being expressed, mean the great Homer, and we Romans mean Virgil.
The law of the nations is common to all mankind, for nations have established certain laws, as occasion and the necessities of human life required. Wars arose, and in their train followed captivity and then slavery, which is contrary to the law of nature; for by that law all men are originally born free. Further, by the law of nations almost all contracts were at first introduced, as, for instance, buying and selling, letting and hiring, partnership, deposits, loans returnable in kind, and very many others.
3. Our law is written and unwritten, just as among the Greeks some of their laws were written and others were not written. The written part consists of leges (lex), plebiscita, senatusconsulta, constitutiones of emperors, edicta of magistrates, and responsa of jurisprudents [i.e., jurists].
4. A lex is that which was enacted by the Roman people on its being proposed by a senatorian magistrate, as a consul. A plebiscitum is that which was enacted by the plebs on its being proposed by a plebeian magistrate, as a tribune. The plebs differ from the people as a species from its genus, for all the citizens, including patricians and senators, are comprehended in the populi (people); but the plebs only included citizens [who were] not patricians or senators. Plebiscita, after the Hortensian law had been passed, began to have the same force as leges.
9. The unwritten law is that which usage has established; for ancient customs, being sanctioned by the consent of those who adopt them, are like laws.

III. The Law of Persons.
All our law relates either to persons, or to things, or to actions. Let us first speak of persons; as it is of little purpose to know the law, if we do not know the persons for whose sake the law was made. The chief division in the rights of persons is this: men are all either free or slaves.
1. Freedom, from which men are said to be free, is the natural power of doing what we each please, unless prevented by force or by law.
2. Slavery is an institution of the law of nations, by which one man is made the property of another, contrary to natural right.
3. Slaves are denominated servi, because generals order their captives to be sold, and thus preserve them, and do not put them to death. Slaves are also called mancipia, because they are taken from the enemy by the strong hand.
4. Slaves either are born or become so. They are born so when their mother is a slave; they become so either by the law of nations, that is, by captivity, or by the civil law, as when a free person, above the age of twenty, suffers himself to be sold, that he may share the price given for him.
5. In the condition of slaves there is no distinction; but there are many distinctions among free persons; for they are either born free, or have been set free.

The Lex Aquileia
2. To kill wrongfully is to kill without any right: consequently, a person who kills a thief is not liable to this actio, that is, if he could not otherwise avoid the danger with which he was threatened.
3. Nor is a person made liable by this law who has killed by accident, provided there is no fault on his part, for this law punishes fault as well as wilful wrong-doing.
4. Consequently, if anyone playing or practicing with a javelin pierces with it your slave as he goes by, there is a distinction made; if the accident befalls a soldier while in the camp, or other places appropriated to military exercises, there is no fault in the soldier, but there would be in anyone else besides a soldier, and the soldier himself would be in fault if he inflicted such an injury in any other place than one appropriated to military exercises.
5. If, again, anyone, in pruning a tree, by letting a bough fall, kills your slave who is passing, and this takes place near a public way, or a way belonging to a neighbor, and he has not cried out to make persons take care, he is in fault; but if he has called out, and the passer-by would not take care, he is not to blame. He is also equally free from blame if he was cutting far from any public way, or in the middle of a field, even though he has not called out, for by such a place no stranger has a right to pass.
6. So, again, a physician who has performed an operation on your slave, and then neglected to attend to his cure, so that the slave dies, is guilty of a fault.
7. Unskillfulness is also a fault, as, if a physician kills your slave by unskillfully performing an operation on him, or by giving him wrong medicines.