Simple convalidation
If the impediment to a marriage is a defective consent by one or both parties, a simple renewal of consent removes the impediment and can effect validation. When a couple has received a dispensation, the partners may validate the marriage by a simple renewal of consent according to canonical form as a new act of the will.can. 1157 CIC/83. When the impediment had affected only one of the parties and the other was unaware of the impediment, only the one aware of the impediment must renew consent. If the impediment is known to both parties, or the impediment is public, then a public renewal of consent by both parties is required.Radical sanation
A bishop can give a dispensation to an impediment, giving the marriage retroactive validation called radical sanation or ''sanatio in radice'' (Latin: "healing in the root"). Some impediments can only be dispensed by the pope, others may be dispensed by the diocesan bishop, while others cannot be dispensed (consanguinity in the direct line or in the second degree of the collateral line).can. 1078, ยง3 CIC/83 ''Sanatio in radice'' retroactively dispenses the impediment and makes a putative marriage valid from the time the ''sanatio'' is granted.can. 1161, 1 CIC/83 The ''sanatio'' validates a marriage by reason of a consent formerly given, but ineffective because of an impediment. When the impediment is removed or dispensed, the consent is ''ipso facto'' ratified and no renovation is required. In such a case, it is requisite that the consent of both parties to the marriage had not ceased and that their marriage had had the external appearance of a true marriage.References
Bibliography
Code of Canon Law - Wm. Woestman, Canon Law of the Sacraments for Parish Ministry, Ottawa 2007. {{Catholic, wstitle=Validation of Marriage Catholic matrimonial canon law Marriage in the Catholic Church