Prior to English rule, Ireland had its own indigenous system of law dating from Celtic times, which survived until the 17th century when it was finally supplanted by the English common law. This native system of law, known as the Brehon law, developed from customs which had been passed on orally from one generation to the next. In the 7th century AD the laws were written down for the first time. Brehon law was administered by Brehons (or brithem). They were the successors to Celtic druids and while similar to judges; their role was closer to that of an arbitrator. Their task was to preserve and interpret the law rather than to expand it.
In many respects Brehon law was quite progressive. It recognised divorce and equal rights between the genders and also showed concern for the environment. In criminal law, offences and penalties were defined in great detail. Restitution rather than punishment was prescribed for wrongdoing. Cases of homicide or bodily injury were punishable by means of the eric fine, the exact amount determined by a scale. Capital punishment was not among the range of penalties available to the Brehons. The absence of either a court system or a police force suggests that people had strong respect for the law.
The first encroachment on Brehon law came in 1155, when Pope Adrian IV issued the Bull Laudabiliter endorsing King Henry II's plan to conquer Ireland. This was followed by the Anglo-Norman invasion led by the Earl of Pembroke, Richard de Clare (Strongbow) in 1169. In 1171 King Henry II held a Council (known as the Curia Regis or King's Council) at Waterford. It declared that "the laws of England were by all freely received and confirmed." This declaration was more aspirational than realistic. English law was initially applied in most of the province of Leinster, where Henry II had granted feudal land rights to Strongbow. In 1172 Henry appointed Hugh de Lacy as the first Justiciar of Ireland (the king's representative).
In 1204 King John authorised the issuing of writs, essentially directing the Irish courts to apply the common law. In 1226 King Henry III ordered the Justiciar to adhere to the laws and customs of England. A year later, a Register of Writs, containing copies of all the writs issued by the English courts, was sent to Dublin. The first recorded appointment of an Anglo-Norman judge came in 1221. English law declined in influence during the 14th and 15th centuries, during which time the Normans, through inter-marriage with the native Irish, were said to have become 'more Irish than the Irish themselves.'
England sought to re-assert the supremacy of its Parliament and of English law over any Irish Parliament or Irish legislation by enacting the Statutes of Kilkenny in 1366. This was followed by the enactment of two statutes at a Parliament held in Drogheda in 1494, together known as Poyning's Law, which provided that the King's Privy Council must give prior assent to the assembly of an Irish Parliament and to the introduction of any specific legislation in the Irish Parliament, and that all laws passed in England applied to Ireland. Despite this, by 1500 English law was confined to an area known as the Pale, made up of Dublin and the east coast. Beyond the Pale, Brehon law continued to be applied.
It was not until the reign of King Henry VIII in the mid-16th century that English law extended further. He implemented a scheme of 'surrender and re-grant' of the land held by native noble families, which brought them within the feudal system of land tenure. Moreover, the King's break with the Roman Catholic Church led to the dissolution of the monasteries and the re-distribution of church land. English law gained a further foothold following the 'Flight of the Earls' from Ulster in 1607 and the consequent Plantation which saw the land being granted to Scottish and English settlers. The Flight of the Earls had an added significance in that it removed the Brehons' remaining source of patronage.
In the cases of Gavelkind (1605) Dav. 49 and Tanistry (1607) Dav. 28, the courts in Ireland rejected the Brehon rules of succession in favour of the English law of succession. In the latter case, the court, applying the rule of recognition, held that the native laws of a country survived if they were reasonable, certain, of immemorial usage and compatible with crown sovereignty. The court held that the native law failed to meet these requirements. The end of the Brehon Law's authority was signalled by the Proclamation of King James I in 1603, which received the Irish people into the King's protection. The country was subsequently divided into counties and English law was administered throughout the country.
More information on the history of the law from 1691 to the present.