Natural marriage
Natural marriage is the name given in Catholic Church canon law to the lawful union of a man and a woman from any type of religious backround. It is a legal pre-requisite to sacramental marriage or Catholic marriage. [1]¯[2]
Natural marriage
Catholic and Jewish
A marriage between a Catholic and a Jew is natural because the Jewish partner is not baptized. If the partner is baptized, then the marriage is sacramental.
Catholic and Muslim
Same as Catholic and Jewish.
Catholic and Agnostic/Atheist
Same as above.
Catholic and Buddhist/Hindu
Same as above
Catholic and Mormon/Jehovah's Witness
A marriage between a Catholic and a Mormon or a Jehovah's Witness, even though the non-Catholic partner considers his or herself Christian, is merely a natural marriage because the second partner is not baptized in the name of the Holy Trinity. The Catholic Church requires a valid trinitarian baptism in order for the marriage to be considered sacred.
Sacramental marriage
Catholic and Protestant
A marriage between a Catholic and a Protestant is more than natural, it is sacramental because both are baptized in the name of the Holy Trinity. Non-Trinitarian Protestants such as Mormons or Jehovah's Witnesses are not united in sacramental vows.
Catholic and Orthodox=
Although there are a few differences in Trinitarian theology for Catholics and Orthodox, a marriage between a Catholic and an Orthodox is considered sacramental because the theological differences are fairly minor.
Gender rules
The Church does not make any particular rules on who transmits the faith, be it men or women, mothers or fathers. On the contrary, certain religions, such as Judaism and Islam, put a priority on the male or on the female in the education of children. This difference in attitude has had a determining impact on general inter-faith relations and policies towards other religions.
Re-marriages
Re-marriages are allowed when a natural marriage becomes a sacramental marriage. However, if a Protestant becomes Catholic and has already been married to another Protestant, then the first marriage has priority since it is already sacramental. Under certain situations, re-marriage can be juridically similar to polygamy.
Un-natural marriages
Any marriage that is non-monogamous (polygamy), non-heterosexual (gay marriage) and non-human (bestiality) is an un-natural marriage in what the Church calls natural law.