The Act for the Settlement of Ireland imposed penalties including death and land confiscation against participants and bystanders of the Irish Rebellion of 1641 and subsequent unrest.
The act was passed on 12 August 1652 by the Rump Parliament of England, who had taken power after the Second English Civil War and had agreed to the Cromwellian conquest of Ireland. The conquest was deemed necessary as Royalist supporters of Charles II of England had allied themselves with the Confederation of Kilkenny (the confederation formed by Irish Catholics during the Irish Confederate Wars) and so was a threat to the newly formed English Commonwealth. The Rump Parliament had a large independent Dissenter membership who strongly empathised with the plight of the Protestant settler community in Ireland, who had suffered greatly at the start of the Irish Rebellion of 1641 and whose suffering had been exaggerated by Protestant propaganda, so the act was also a retribution against Irish Catholics who had participated in the initial stages of the war.
Whereas the Parliament of England, after the expense of much blood and treasure for suppression of the horrid rebellion in Ireland, have by the good hand of God upon their undertakings, brought that affair to such an issue, as that a total reducement and settlement of that nation may, with God's blessing, be speedily effected...
-Act for the Settlement of Ireland 1652 Preamble
Ten named leaders of the Royalist forces in Ireland, together with anyone who had participated in the Irish Rebellion's early stages and who had killed an Englishman other than in battle, lost their lives and estates.
The Act made a distinction between the rebels of 1641 - who were deemed unlawful combatants - as against those who had fought in the regular armies of Confederate Ireland, who were treated as legitimate combatants provided that they had surrendered before the end of 1652. The 1641 rebels and the above mentioned Royalist leaders were not included in the pardon given to soldiers who had surrendered: they were to be executed when captured. Roman Catholic clergy were also excluded from the pardon, as the Cromwellians held them responsible by fomenting the 1641 Rebellion.
The remaining leaders of the Irish army lost two-thirds of their estates. To have been merely a bystander was itself a crime, and anyone who had resided in Ireland any time from 1 October 1649, to 1 March 1650 and had not "manifested their constant good affection to the interest of the Commonwealth of England" lost one-third of their land. The Commissioners in Ireland had power to give them, in lieu thereof, other (poorer) lands in Connacht or Clare in proportion of value and were authorised "to transplant such persons from the respective places of their usual habitation or residence, into such other places within that nation, as shall be judged most consistent with public safety."
This was interpreted by the English Parliamentarian authorities in Ireland who ordered all Irish land owners to leave for those lands before 1 May 1654 or be executed. However, in practice, most Catholic landowners stayed on their land as tenants and the numbers of those either transplanted or executed was small.
Protestant Royalists, on the other hand, could avoid land confiscations if they had surrendered by May 1650 and had paid fines to the Parliamentarian government. The Commonwealth initially had harsh plans to remove the Scottish Presbyterians from north east Ulster - as they had fought with the Royalists in he latter stages of the war. However this was reversed in 1654, and it was ruled that the plantation would apply to Catholics only.
In Irish popular memory of the Cromwellian Plantation, the Commonwealth is said to have declared that the Irish must go, "to Hell or to Connaught". However according to historian Padraig Lenihan, "The Cromwellians did not proclaim 'To Hell or to Connaught' and Clare and Connaught were chosen as a native reservation not because the land was poor, The Commonwealth rated Connaught above Ulster in this respect". Lenihan suggests that the western province was chosen instead for security reasons - to keep Catholic landowners penned between the sea and the river Shannon.
In the next of the Plantations of Ireland, the confiscated land was granted to the "Adventurers". The new owners were known as "planters". The Adventurers were financiers who had loaned the Parliament £10 million in 1642 at the start of the Wars of the Three Kingdoms (see Adventurers Act). Many of Ireland's pre-war Protestant inhabitants also took advantage of the confiscation of Catholic-owned land to increase their own holdings. In addition, smaller grants of land were given to 12,000 veterans of the New Model Army who had served in Ireland.
In June 1657, the Act of Settlement 1657 "for the Assuring, Confirming and Settling of lands and estates in Ireland" ratified previous decrees, judgments, grants and instructions made or given by the various officers and councils in applying the 1652 Act.
All Ordinances and Acts of Parliament passed during the English Civil War and the Interregnum were considered void after the English Restoration as they had not received Royal assent.
In 1662, an Act of Settlement 1662 (after the Restoration) aimed to reduce its effect on Protestant and "innocent Catholics." This Act returned some lands to prominent Irish Royalists, but left most of the land confiscated from Irish Catholics in Protestant hands. This was similar to the post-Restoration situation in England, where Church and Royal lands were returned by Act of Parliament, but other confiscated Royalist lands could only be regained through civil litigation.