§ 45 Legal and Historical Sources
Though the formal source of the law is one, its material sources are many, and they are divisible into two classes which may be distinguished as legal and historical. The former are those sources which are recognised as such by the law itself. The latter are those sources which are such in fact, but are nevertheless destitute of legal recognition. This is an important distinction which calls for careful consideration. In respect of its material origin a rule of law is often of long descent. The immediate source of it may be the decision of an English court of justice. But that court may have drawn the matter of its decision from the writings of some lawyer, let us say the celebrated Frenchman, Pothier; and Pothier in his turn may have taken it from the compilations of the Emperor Justinian, who may have obtained it from the praetorian edict. In such a case all these things—the decision, the works of Pothier, the corpus juris civilis, and the edictum perpetuum—are the successive material sources of the rule of English law. But there is a difference between them, for the precedent is the legal source of the rule, and the others are merely its historical sources. The precedent is its source not merely in fact, but in law also; the others are its sources in fact, but obtain no legal recognition as such. Our law knows well the nature and effect of precedents, but it knows nothing of Pothier, or of Tribonian, or of the Urban Praetor. The proposition that every principle embodied in a judicial decision has for the future the force of law is not merely a statement of historical fact as to the growth of English law; it is itself a rule of law. But the proposition that much of the law of Rome has become incorporated into the law of England is simply a statement of fact, which has in law no relevance or recognition.
The legal sources of law are authoritative, the historical are unauthoritative. The former are allowed by the law courts as of right; the latter have no such claim; they influence more or less extensively the course of legal development, but they speak with no authority. No rule of law demands their recognition. Thus both the statute-book and the works of Jeremy Bentham are material sources of English law. The historians of that system have to take account of both of them. Much that is now established law has its source in the ponderous volumes of the great law-reformer. Yet there is an essential difference between the two cases. What the statute-book says becomes law forthwith and ipso jure; but what Bentham says may or may not become law, and if it does, it is by no claim of right but solely through the unconstrained good pleasure of the legislature or the courts. So the decisions of English courts are a legal and authoritative source of English law, but those of American courts are in England merely an historical and unauthoritative source. They are treated with respect by English judges, and are in fact the ground and origin of an appreciable portion of English law, but their operation is persuasive merely, not authoritative, and no rule of English law extends recognition to them.
The legal sources are the only gates through which new principles can find entrance into the law. Historical sources operate only mediately and indirectly. They are merely the various precedent links in that chain of which the ultimate link must be some legal source to which the rule of law is directly attached.
We are here concerned solely with the legal sources of the law. Its formal source is involved in the definition of the law itself, and has been already sufficiently dealt with. Its historical sources pertain to legal history, not to legal theory. Hereafter, when we speak of the sources of law, we shall mean by that term the legal sources exclusively.
It may help us to attain a clearer understanding of a somewhat difficult matter if we attempt to reach a definition of these sources from another standpoint. In every progressive community the law undergoes a continuous process of growth and change. This process of legal evolution does not proceed by haphazard. It is not left to the discretion of the judges to apply one law to-day and another to-morrow, for the growth of the law is itself a matter governed by the law. Every legal system contains certain rules determining the establishment of new law and the disappearance of old. That is to say, it contains certain rules to this effect: that all new principles which conform to such and such requirements are to be recognised as new principles of law, and applied accordingly in substitution for, or as supplementary to the old. Thus it is itself a principle of English law that any principle involved in a judicial decision has the force of law. Similar legal recognition is extended to the law-producing effect of statutes and immemorial customs. Rules such as these establish the sources of the law. A source of law, then, is any fact which in accordance with the law determines the judicial recognition and acceptance of any new rule as having the force of law. It is the legal cause of the admittance by the judicature of any new principle as one which will be observed for the future in the administration of justice.