Laicization is easier to understand if you think, not in terms of priesthood and sacramental ordination, but in terms of the clerical state and clerical status.  Laicization at least assumes the validity of ordination, but definitively removes the authority of the cleric to act as a cleric would except in emergencies and other closely defined instances (like teaching in a Catholic school, college, university or seminary).  The only other status that church law recognizes is the lay state, hence a man [sic] who has lost his clerical "privileges" is said to be "reduced to the lay state," to obviate any consideration of the laicized man exercising clerical or priestly functions without further action by the Holy See.