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, which 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 settlers of the Ulster Plantation, 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.
Also money to pay for the wars had been raised under the 1642 Adventurers Act, which paid creditors with land forfeited by the 1641 rebels. These and other creditors had mostly resold their property interests to local landowners who wanted these recent property transfers reconfirmed by an over-riding Act, for the avoidance of doubt.
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...