On 4 November 1461, Act of Attainder.
An attainder was a legal device used by Parliament to strip somebody of their rights, titles, or lands, or all of those. They could be applied solely to the person in question, who would be a traitor to the realm, or have it applied to their heirs as well. The latter was usually reserved for the most serious offenders, where they held a
position or title of considerable significance, such as a claim to the crown.
In the November 1461 Parliament, such a set of attainders were issued for the leading Lancastrians. It was unusual for any noblewoman to be attained, but Margaret of Anjou‘s actions were considered worthy of such.
A separate document of attainder was drawn up for lesser nobles, knights and gentry who had fought against
Edward.
Margaret, in consideration of her transgressions and offences… [be] convicted and attainted of high treason. And that the same Margaret and also the said Edward her son shall be legally unable, and taken, held, deemed and considered unable and unworthy, to have, occupy, hold, inherit or enjoy any estate, name of dignity, preeminence or possessions … the same Margaret and Edward her son shall forfeit to our said liege lord King Edward IV all the castles, manors, lordships, honours, lands and tenements… And also that the said Henry, Duke of Somerset, Thomas Courtenay, late earl of Devon, Henry, late earl of Northumberland, Thomas, Lord
Roos, John, late Lord Clifford, and John, late Lord Neville, shall be legally unable forever henceforth to have, hold, inherit or enjoy any name of dignity, estate or pre-eminence within the same realm…
This Act of Attainder was part of the Yorkist regimes moves to legitimise its rule via legal means. It also enabled Edward IV to grant confiscated lands and titles to those who had supported him in as he seized the crown. Most of those attainted had fought against the Yorkists at Towton, with separate action being taken by the same parliament in respect of others who had fought for the Lancastrians in the Battle of Wakefield.