They were partially eclipsed by the Norman invasion of 1169, but underwent a resurgence from the 13th until the 17th century, over the majority of the island, and survived into Early Modern Ireland in parallel with English law.
The laws were a civil rather than a criminal code, concerned with the payment of compensation for harm done and the regulation of property, inheritance and contracts; the concept of state-administered punishment for crime was foreign to Ireland's early jurists.
They show Ireland in the early medieval period to have been a hierarchical society, taking great care to define social status, and the rights and duties that went with it, according to property, and the relationships between lords and their clients and serfs.
For instance, historians have seen similarities between Irish and Indian customs of fasting as a method of shaming a wrongdoer to recover a debt, or to demand the righting of a wrong.
[10] Today, the legal system is assumed to contain some earlier law influenced by the church, and adaptation through methods of reasoning the Irish jurists would have sanctioned.
[18] Cáin Adomnáin, a Christian Law, promulgated by the Synod of Birr in 697, sought to raise the status of women of that era, although the actual effect is unknown.
[citation needed] Divorce was provided for on a number of grounds (that ultimately deal with the inability to have a child), after which property was divided according to what contribution each spouse had made to the household.
A husband was legally permitted to hit his wife to "correct" her, but if the blow left a mark she was entitled to the equivalent of her bride-price in compensation and could, if she wished, divorce him.
[21][22] Under Western Catholic church law, women were still largely subject to their fathers or husbands and were not normally permitted to act as witnesses, their testimony being considered "biased and dishonest".
In particular, Críth Gablach gives a highly schematized and unrealistic account of how the king spends his week: Sunday is for drinking ale, Monday is for judging, Tuesday is for playing fidchell, Wednesday is for watching hounds hunt, Thursday is for sexual union, Friday is for racing horses, and Saturday is for judging (a different word from Monday, but the distinction is unclear).
The Irish law texts describe a highly segmented world, in which each person had a set status that determined what legal tasks they could undertake and what recompense they could receive when a crime was committed against them.
Críth Gablach and Uraicecht Becc are two of the main texts focusing on lay landholders, the latter of which also briefly covers the status of skilled individuals and of clerics.
Anthropologist David Graeber suggests this indicates a significant trade in female slaves was present not long before the laws were written.
[42] The three ranks of commoners, at least according to the status tract, vary in the type of clientship they undertook and the property they could hold, though it is unclear how this worked in practice.
[50] Because of that stipulation, the position of briugu was potentially ruinous, and this outcome is portrayed in a number of tales such as in Togail Bruidne Da Derga and Scela Mucce Meic Datho.
A poorer man could become a "base client" by selling a share in his honour price, making his lord entitled to part of any compensation due him.
The legal text Bretha Déin Chécht "The Judgments of Dían Cécht" goes into considerable detail in describing the fines based on the location of the wound, the severity, and in some cases the type.
[citation needed] Early Irish law recognised a number of degrees of agnatic kinship, based on a belief that there was a common male ancestor.
Some do seem to represent a legal theory, such as the maxim in Bechbretha that "no-one is obliged to give something to another for nothing" and that in Bretha Crólige that "the misdeed of the guilty should not affect the innocent".
This is a concept apparently borrowed from, or at least akin with, European legal theory, and reflects a type of law that is universal and may be determined by reason and observation of natural action.
Since acting as a ráth could mean a financial loss that might not be repaid, the law tracts apparently see the position as dangerous, as one of three "dark things of the world.
The most famous of these is Cáin Adomnáin, which was apparently created in 697 under the influence of Adomnán and ratified by a number of ecclesiastics and kings whose names appear in the text.
In addition to the similarities and evidence of borrowing from Canon law and the Bible, scholars who hold this position ask how any non-Clerics could have been sufficiently literate at this period to create the texts.
It became his duty to give a historical retrospect, and in doing so he exhibited "all the judgments of true nature which the Holy Ghost had spoken from the first occupation of this island down to the reception of the faith.
[99] "Branched Purchase" is the title of what is perhaps the most well-known tract on status and certainly the most accessible, as a modern printed edition (though not a translation) has been published by the Dublin Institute for Advanced Studies.
The Middle Irish text, The Distribution of Cró and Dibad deals with extracting fines from a killer and dividing a dead man's property.
[107] Additionally, the legal text Cóic Conara Fugill (the Five Paths of Judgment) was originally written during the earliest period but received a number of subsequent recensions afterwards.
One of the first changes came with the Synod of Cashel in 1172, which required single marriages to partners that were not closely related, and exempted clergy from paying their share of a family's eraic payments.
Henry II, who created the Lordship of Ireland, was also a legal reformer within his empire, and started to centralise the administration of justice and abolish local customary laws.
The Tudor conquest of Ireland in the mid-16th century, ending in the Nine Years' War (1594–1603), caused Tanistry and Gavelkind, two cornerstones of the Brehon Laws, to be specifically outlawed in 1600.