§1. Whenever an impediment is discovered after everything has already been prepared for the wedding, and the marriage cannot be delayed without probable danger of grave harm until a dispensation is obtained from the competent authority, the local ordinary and, provided that the case is occult, all those mentioned in can. 1079, §§2-3 when the conditions prescribed therein have been observed possess the power of dispensing from all impediments except those mentioned in can. 1078, §2, n. 1.
§2. This power is valid even to convalidate a marriage if there is the same danger in delay and there is insufficient time to make recourse to the Apostolic See or to the local ordinary concerning impediments from which he is able to dispense.
Source: Code of Canon Law (Vatican.va)