The religious struggles of the 17th century left a deep sectarian division in Ireland . Religious allegiance now determined the perception in law of loyalty to the Irish King and Parliament . After the passing of the Test Act 1672 , and with the victory of the forces of the dual monarchy of William and Mary over the Jacobites , Roman Catholics and nonconforming Protestant Dissenters was barred from sitting as members in the Irish Parliament . Under the emerging Penal Laws , Irish Roman Catholics and Dissenters was increasingly deprived of various and sundry civil rights even to the ownership of hereditary property . Additional regressive punitive legislation followed 1703 , 1709 and 1728 . This completed a comprehensive systemic effort to materially disadvantage Roman Catholics and Protestant Dissenters , while enriching a new ruling class of Anglican conformists . The new Anglo @-@ Irish ruling class became known as the Protestant Ascendancy .