Books of authority


Books of authority is a term used by legal writers to refer to a number of early legal textbooks that are excepted from the rule that textbooks are not treated as authorities by the courts of England and Wales and other common law jurisdictions.
These books are treated by the courts as authoritative statements of the law as it was at the time at which they were written, on the authority of their authors alone. Consequently, they are treated as authoritative statements of the law as it is at the present time, unless it is shown that the law has changed, and may be cited and relied on in court as such.
The statements made in these books are presumed to be evidence of judicial decisions which are no longer extant. The primary reason for this practice is the difficulty associated with ascertaining the law of the medieval and early modern periods.
On the subject of this practice, William Blackstone said:

Abridgements of the year books

Fitzherbert

On the common law

Glanvill

Traditionally, Ralph de Hengham was believed to be a prolific author of common law procedural treatises, and numerous works were attributed to him. These included not only the eponymous Hengham parva and Hengham magna, but also "Cum sit necessarium", "Exceptiones ad Cassandum Brevia", "Fet Asaver", "Judicium Essoniorum", and "Modus Componendi Brevia", among others. More recent scholarly analysis, however, reveals that only the Parva is conclusively his. Hengham may also have written two consultations.

Littleton