The Church has liberalized its teaching on Marriage. While a marriage between Catholics must take place in a Catholic Church a marriage between a Catholic and a Protestant do not.Before Vatican II mixed marriages were forbidden.
On Christian Marriage
*CASTI CONNUBII *ENCYCLICAL OF POPE PIUS XI ON CHRISTIAN MARRIAGE DECEMBER 31, 1930
82. They, therefore, who rashly and heedlessly contract mixed marriages, from which the maternal love and providence of the Church dissuades her children for very sound reasons, fail conspicuously in this respect, sometimes with danger to their eternal salvation. This attitude of the Church to mixed marriages appears in many of her documents, all of which are summed up in the Code of Canon Law: “Everywhere and with the greatest strictness the Church forbids marriages between baptized persons, one of whom is a Catholic and the other a member of a schismatical or heretical sect; and if there is, add to this, the danger of the falling away of the Catholic party and the perversion of the children, such a marriage is forbidden also by the divine law.”
Now, the Church accepts mixed marriages. A priest can even assist at the wedding in a Protestant Church.
“For appropriate pastoral reasons, a bishop can grant a
dispensation from the Catholic form of marriage and can permit the marriage to take place in a non-Catholic church with a non-
Catholic minister as the officiating minister. A priest may not
only attend such a ceremony but may also address, pray with, and bless the couple.”
ewtn.com/library/MARRIAGE/MIXED.TXT