For ye were as sheep going astray; but are now returned unto the Shepherd and Bishop of your souls.
1 Peter 2:25
We declare forever infamous, and deprived of their rights, and condemned to exile, all heretics of either sex, whatever be their name; their property shall be confiscated without hope of restoration, or of being transmitted to their children by hereditary succession, because crimes which attack the majesty of God are infinitely more grievous than those which attack the majesty of earthly princes. With regard to those who are strongly suspected of heresy, if, after having been ordered by the church, they do not demonstrate their innocence by suitable testimony, they also shall be declared infamous, and condemned to exile.
(Codex Justinianus, lib. 1, tit. 5, n. 19; cited in ‘Library of Translations: The Power of the Pope during the Middle Ages,’ M. Gosselin (R. C.), Vol. I, pp. 83, 84 London: C. Dolman, 1853
Those condemned for heresy are punished by a secular judge, and the goods of lay heretics are confiscated, and the goods of clerics are applied to the churches where they were benefited.
Gregorius IX. Decretalium compilatio. Trans. by Google. https://www.intratext.com/IXT/LAT0833/
Temporal princes shall be reminded and exhorted, and if need be, compelled by spiritual censures, to discharge every one of their functions; and that, as they desire to be reckoned and held faithful, so, for the defense of the faith, let them publicly make oath that they will endeavor, bona fide with all their might, to extirpate from their territories all heretics marked by the church; so that when any one is about to assume any authority, whether spiritual or temporal, he shall be held bound to confirm his title by this oath. And if a temporal prince, being required and admonished by the church, shall neglect to purge his kingdom from this heretical [de]pravity, the metropolitan and other provincial bishops shall bind him in fetters of excommunication; and if he obstinately refuse to make satisfaction this shall be notified within a year to the Supreme Pontiff, that then he may declare his subjects absolved from their allegiance, and leave their lands to be occupied by Catholics, who, the heretics being exterminated, may possess them unchallenged, and preserve them in the purity of the faith.
The Decretals of Gregory IX, book 5, title 7, chapter 13. Translated.