The form of marriage refers to the wedding ceremony; the ritual used to exchange consent. Catholics must follow the Catholic form of marriage. Even if only one of the parties is Catholic, the Catholic form must be followed.[3]
For Catholics belonging to the Western, Latin Rite Church, the form requires that consent be exchanged in the presence of a cleric, in accordance with the approved liturgical rite, and witnessed by two other people.[4] The cleric assisting at the wedding must have the proper authority to witness the marriage in the name of the Church. In certain circumstances, when a genuine shortage of priests and deacons exists, members of the lay faithful can receive delegation from the diocesan bishop to assist at marriages.[5]
In the Eastern Catholic Churches, the required form is a bit different. "Only those marriages are valid which are celebrated with a sacred rite, in the presence of the local hierarch, local pastor, or a priest who has been given the faculty of blessing the marriage by either of them, and at least two witnesses." [6]
The "sacred rite" means a priest must assist and give a blessing.[7] Contrary to the discipline of the Western Catholic Church, the nuptial blessing is required for validity in the Eastern Catholic Churches. A deacon cannot assist at a marriage because he cannot give the nuptial blessing. If an Eastern Rite Catholic contracts marriage with a member of an Eastern Orthodox Church according to the laws of the Orthodox Church, but without the permission of the Catholic hierarch, the marriage is valid if the nuptial blessing was given by a priest.[8]
In certain circumstances, the local ordinary or hierarch can dispense from the required form of marriage. However, if a Catholic attempts marriage and neglects the proper form of marriage, the marriage is invalid.