Can anyone tell me if it was possible for Pope Sixtus IV to issue a bull declaring Ferdinand and Isabella's marriage invalid? The marriage was rather dodgy since Isabella had promised in writing not to marry without her brother, Enrique IV's permission, and her marriage to Ferdinand was to a cousin (AFAIK without the due dispensation (which IMHO is the reason why they were so ready to make sure the due process was followed with Catherine of Aragon's remarriage).).
And were Sixtus to declare the marriage unlawful, what would the fallout be?
And were Sixtus to declare the marriage unlawful, what would the fallout be?