Brehon law was an early Irish legal system administered by traveling judges. In 1169, the Norman Strongbow invaded Ireland and helped the King of Leinster take control of Dublin and Waterford. King Henry II then established English common law and a court system. Over time, the Normans adopted Irish customs. In 1494, Poyning's Law required Irish laws to be approved by England. Ireland was then fully under British rule by the 1600s. The 1937 Irish Constitution established independence by removing allegiance to Britain.