§ 63 Authoritative and Persuasive Precedents
Decisions are further divisible into two classes, which may be distinguished as authoritative and persuasive. These two differ in respect of the kind of influence which they exercise upon the future course of the administration of justice. An authoritative precedent is one which judges must follow whether they approve of it or not. It is binding upon them and excludes their judicial discretion for the future. A persuasive precedent is one which the judges are under no obligation to follow, but which they will take into consideration, and to which they will attach such weight as it seems to them to deserve. It depends for its influence upon its own merits, not upon any legal claim which it has to recognition. In other words, authoritative precedents are legal sources of law, while persuasive precedents are merely historical. The former establish law in pursuance of a definite rule of law which confers upon them that effect, while the latter, if they succeed in establishing law at all, do so indirectly, through serving as the historical ground of some later authoritative precedent. In themselves they have no legal force or effect.
The authoritative precedents recognised by English law are the decisions of the superior courts of justice in England. The chief classes of persuasive precedents are the following:
(1) Foreign judgments, and more especially those of American courts.155
(2) The decisions of superior courts in other portions of the British Empire, for example, the Irish courts.156
(3) The judgments of the Privy Council when sitting as the final court of appeal from the Colonies.157
(4) Judicial dicta, that is to say, statements of law which go beyond the occasion, and lay down a rule that is irrelevant or unnecessary for the purpose in hand. We shall see later that the authoritative influence of precedents does not extend to such obiter dicta, but they are not equally destitute of persuasive efficacy.158