I found an example of where the bishop gave permission for a couple to recieve the nuptial blessing where the couple was in fact living in sin. Of course they had to live apart and perform a public penance in order to repair the damage that was done by their scandal. The bishop also legitimated their children.
1795 Aug. 10
Penalver y Cardenas, Luis Bishop
(New Orleans)
The Bishop decrees:
1) That having examined these docuмents concerning Dionisio Landry's petition for a dispensation to marry Constanza Melanzon, he dispenses them from the impediment of consanguinity and considers as legitimate any children they may have.
2) Moreover, he ordains that the parties must cease living under the same roof for the present and must make a general confession so that they may restore with their example all they have destroyed by their scandal.
3) In order to absolve them from their fault, the Bishop ordains that during the publication of the banns, they must daily pray on their knees the three parts of the rosary and contribute twenty pesos of alms to their parish.
4) To this end, the Bishop ordains that the decree be sent to the pastor of the parish of Iberville, so that the latter may impart the nuptial blessings. Signed by the Bishop and witnessed by Joseph Maria rivas, Secretary.
--To this docuмent is added a note by Rivas certifying that at New Orleans on the same day he notified Dionisio Landry of the above decree.
--Finally, is added another note by Rivas that the decree of the Bishop was sent to the pastor Buenaventura de Castro of Iberville parish.
IV-5-b A.D.S. 11pp. 8vo. (Spanish)
http://archives.nd.edu/mano/17950824.htm