We are about to look at the Penal Laws that the British monarchy enacted upon the Irish. However, before we do, we need to look at the old laws that governed the Irish prior to the British invasion.
Early Irish law refers to the statutes that governed everyday life and politics in Ireland during the Gaelic period. Thought to be the oldest form of law in Northern Europe, they were partially eclipsed by the Norman invasion of 1169, but underwent a resurgence in the 13th century, and survived in parallel with English law over the majority of the island until the 17th century. "Early Irish Law" was often, although not universally, referred to within the law texts as "Fenechas", the law of the Feni, or the freemen of Irelandian Ireland mixed with Christian influence and juristic innovation. These secular laws existed in parallel, and occasionally in conflict, with Canon law throughout the early Christian period.
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.
No single theory as to the origin of early Irish law is universally accepted. Early Irish law consisted of the accumulated decisions of the Brehons, guided entirely by an oral tradition. Some of these laws were recorded in text form by Christian clerics. The early theory to be recorded is contained in the Pseudo-Historical Prologue to the Senchas Már. According to that text, after a difficult case involving St. Patrick, the Saint supervised the mixing of native Irish law and the law of the church. A representative of every group came and recited the law related to that group and they were written down and collected into the Senchas Már, excepting that any law which conflicted with the law of the church was replaced. The story also tells how the law transitioned from the keeping of the poets, whose speech was "dark" and incomprehensible, to the keeping of each group who had an interest in it. The story is extremely dubious as, not only is it written many centuries after the events it depicts, but it also incorrectly dates the collection of the Senchas Már to the time of St. Patrick while scholars have been able to determine that it was collected during the eighth century, at least three centuries after the time of St. Patrick. Some of the ideas in the tale may be correct, and it has been suggested by modern historians the Irish jurists were an offshoot from the poetic class which would have previously preserved the laws.
For some time, especially through the work of D. A. Binchy, the laws were held to be conservative and useful primarily for reconstructing the laws and customs of the Proto-Indo-Europeans just as linguists had reconstructed the Proto-Indo-European language. For instance, historians have seen comparisons between Irish and Indian customs of fasting as a method of shaming a wrongdoer, in order to recover a debt or to demand the righting of a wrong. Other legal institutions prominent in early Irish law but foreign to most contemporary legal systems, such as the use of sureties, have been considered as survivals from earlier periods. More recently historians have come to doubt such attributions. While few historians would argue that all Irish law comes from church influence, they are today much more wary as to what material is a survival and what has changed. A past may still be suggested for a certain legal concept based on Irish legal terms' being cognate with terms in other Celtic languages, although that information does not prove that the practice described by the legal term has not changed.
Today the legal system is agreed to be some mixture of earlier law influenced by the church as well as adaptation through methods of reasoning which the Irish jurists would have sanctioned. It is not, however, agreed as to just how large a role each of these aspects may have played in the creation of the legal texts, but rather it represents an important scope for debate. There is, however, one area where scholars have found material that is clearly old. A number of legal terms have been shown to have originated in the period before the Celtic Languages split up because they are preserved in both Old Irish and in the Welsh legal texts. On the other hand, this is not regarded as unquestionable evidence that the practices described by such terms are unchanged or even have their origins in the same period as do the terms.
Another important aspect when considering the origins is that the early Irish law texts are not always consistent. Early Irish law is, like the Old Irish language, remarkably standard across an Island with no central authority. However, close examination has revealed some variations. Among these one can especially point to variations both in style and content between two of the major legal schools, as they are known; those which produced the Bretha Nemed and Senchas Már respectively.