Early Irish law

Tanistry was a system of inheritance practised by the Gaelic nobilities of Ireland, the Isle of Man, and parts of modern Scotland. It was distinctive in having an elected heir known as the tanist (; ; ). This system was used to select the Chiefs of the Name (head of a clan) and the rulers of the various Gaelic kingdoms in Ireland and in Scotland.

statutes which governed everyday life in Early Medieval Ireland

Brehon (, ) is a term for a historical arbitration, mediative, and judicial role in Gaelic culture. Brehons were part of the system of Early Irish law, which was also simply called "Brehon law". Brehons were judges, close in importance to the chiefs.