From Blackstone’s Commentaries Volume 1, pp. 69-71.
‘But here a very natural, and very material, question arises: how are these customs or maxims to be known, and by whom is their validity to be determined?
The answer is, by the judges in the several courts of justice. They are the depositaries of the laws; the living oracles, who must decide in all cases of doubt, and who are bound by an oath to decide according to the law of the land. The knowledge of that law is derived from experience and study; from the “viginti annorum lucubrationes,” which Fortescue mentions; and from being long persoually accustomed to the judicial decisions of their predecessors.
And indeed these judicial decisions are the principal and most authoritative evidence, that can be given, of the existence of such a custom as shall form a part of the common law. The judgment itself, and all the proceedings previous thereto, are carefully registered and preserved, under the name of records, in public repositories set apart for that particular purpose; and to them frequent recourse is had, when any critical question arises, in the determination of which former precedents may give light or assistance. And therefore, even so early as the conquest, we find the “præteritorum memoria eventorum” reckoned up as one of the chief qualifications of those, who were held to be “legibus patriæ optime instituti.”
For it is an established rule to abide by former precedents, where the same points come again in litigation: as well to keep the scale of justice even and steady, and not liable to waver with every new judge’s opinion; as also because the law in that case being solemnly declared and determined, what before was uncertain, and perhaps indifferent, is now become a permanent rule, which it is not in the breast of any subsequent judge to alter or vary from according to his private sentiments: he being sworn to determine, not according to his own private judgement, but according to the known laws and customs of the land; not delegated to pronounce a new law, but to maintain and expound the old one.
Yet this rule admits of exception, where the former determination is most evidently contrary to reason; much more if it be clearly contrary to the divine law. But even in such cases the subsequent judges do not pretend to make a new law, but to vindicate the old one from misrepresentation. For if it be found that the former decision is manifestly absurd or unjust, it is declared, not that such a sentence was bad law, but that it was not law; that is, that it is not the established custom of the realm, as has been erroneously determined.
And hence it is that our lawyers are with justice so copious in their encomiums on the reason of the common law; that they tell us, that the law is the perfection of reason, that it always intends to conform thereto, and that what is not reason is not law. Not that the particular reason of every rule in the law can at this distance of time be always precisely assigned; but it is sufficient that there be nothing in the rule flatly contradictory to reason, and then the law will presume it to be well founded.
And it hath been an ancient observation in the laws of England, that whenever a standing rule of law of which the reason perhaps could not be remembered or discerned, hath been wantonly broken in upon by statutes or new resolutions, the wisdom of the rule hath in the end appeared from the inconveniences that have followed the innovation.
The doctrine of the law then is this: that precedents and rules must be followed, unless flatly absurd or unjust; for though their reason be not obvious at first view, yet we owe such a deference to former times as not to suppose that they acted wholly without consideration.
To illustrate this doctrine by examples. It has been determined, time out of mind, that… Now this is a positive law, fixed and established by custom, which custom is evidenced by judicial decisions, and therefore can never be departed from by any modern judge without a breach of his oath and the law. For herein there is nothing repugnant to natural justice; though the artificial reason of it, drawn from the feodal law, may not be quite obvious to everybody.And therefore, though a modern judge… might wish it had been otherwise settled, yet it is not in his power to alter it. But if any court were now to determine (otherwise) … no subsequent judges would scruple to declare that such prior determination was unjust, was unreasonable, and therefore was not law. So that the law, and the opinion of the judge, are not always convertible terms, or one and the same thing; since it sometimes may happen that the judge may mistake the law.
Upon the whole, however, we may take it as a general rule, “that the decisions of courts of justice are the evidence of what is common law:” in the same manner as, in the civil law, what the emperor had once determined was to serve for a guide for the future.’