There is internal evidence that it was composed subsequently to the reign of Louis le Débonnaire (778–840), as it contains a Lombard law of that king's, which forbids the testimony of a clerk to be received against a layman.
On the other hand, its style and reasoning is far superior to that of the law writers of the 10th and 11th centuries; while the circumstance that the method of its author has not been in the slightest degree influenced by the school of the Gloss-writers (Glossatores) leads fairly to the conclusion that he wrote before that school became dominant at Bologna.
Savigny, who traced the history of the Brachylogus with great care, is disposed to think that it is the work of Irnerius himself (Geschichte des röm.
Its value is chiefly historical, as it furnishes evidence that a knowledge of Justinian's legislation was always maintained in northern Italy.
The author of the work has adopted the Institutes of Justinian as the basis of it, and draws largely on the Digest, the Code and the Novels; while certain passages, evidently taken from the Sententiae Receptae of Julius Paulus, imply that the author was also acquainted with the Visigothic code of Roman law compiled by order of Alaric II.