The text of the law is found in two manuscripts, one from the fifteenth and one from the seventeenth century, both based on a no-longer-extant manuscript referred to as ‘the Old Book of Raphoe’. One of the manuscripts is a Michéal Ó Cléirigh text of 1627, itself based on a manuscript written by his cousin Címhumhan Ó Cléirigh. The text of the law can be divided into four parts, written by various authors between the seventh and tenth centuries. Paragraphs 1–27 comprise an introduction written in Middle Irish around AD 1000; paragraphs 28–32, in Old Irish, list the guarantors of the law and describe the assembly at Birr at which it was promulgated; paragraph 33, in Latin, is an address by an angel to Adomnán; and paragraphs 34–53, again in Old Irish, are, says John Ryan, ‘the original law in its strict legal form as drafted by the professional brehons and adopted by the assembly [at Birr]’.
