§1. A marriage between two persons, one of whom was baptized in the Catholic Church or received into it, and the other of whom is not baptized, is invalid.
§2. A person is not to be dispensed from this impediment unless the conditions mentioned in cann. 1125 and 1126 have been fulfilled.
§3. If at the time the marriage was contracted one party was commonly held to have been baptized or the baptism was doubtful, the validity of the marriage must be presumed according to the norm of can. 1060 until it is proven with certainty that one party was baptized but the other was not.
Source: Code of Canon Law (Vatican.va)