The Catholic Church strives to teach what Jesus did and to be as compassionate as he was. Jesus confronted hard issues such as divorce and remarriage (Mt.5:31-32, 19:3-12; Mk. 10:2-12; Lk. 16:18). He befriended the Samaritan woman at the well (Jn. 4:4-42) and challenged others to lay down stones of prejudice and harsh judgment (Jn. 8:1-11).
Jesus taught the norm: marriage is a permanent and exclusive partnership between a man and woman for the purposes of giving and receiving love open to the birth and nurture of children. The Catholic Church presumes every legitimate marriage to be valid and binding for life unless proven otherwise. This presumption applies regardless of the baptismal or religious status of the parties, or the place where the wedding occurred.
In the tribunal process, the Church judges whether it has been proven that a specific failed marriage lacked something essential from the beginning and, therefore, is invalid and not binding for life, thus deserving a declaration of nullity .
A process developed in the early Church is the Pauline Privilege. St. Paul upheld Jesus’ teaching with an exception for the departure through divorce of a non-baptized party (1 Cor. 7:8-11 vs. 12-16). Paul’s exception leads to a dissolution of a valid civil marriage. The Church has extended this Pauline Privilege in the Favor of the Faith. These cases are not declarations of nullity, but follow some of the same rules. They are not discussed here, but may apply if either or both spouses
in a failed marriage was/were not baptized Christian." (from Archdiocese of Cincinnati brochure)