VII. The Effects of the Sacrament of Holy Orders
Catechism number 1583
It is true that someone validly ordained can, for a just reason, be discharged from the obligations and functions linked to ordination, or can be forbidden to exercise them; but he cannot become a layman again in the strict sense,75 because the character imprinted by ordination is for ever. the vocation and mission received on the day of his ordination mark him permanently.