Marriage is one of the seven sacraments of the Catholic Church. As such, it is a supernatural institution, as well as a natural one. The Church, therefore, restricts sacramental marriage to men and women who meet certain requirements.
In order to get married in the Catholic Church, you must be:
A Baptized Christian: Both partners do not have to be a Catholic in order to be sacramentally married in the Catholic Church, but both must be baptized Christians (and at least one must be a Catholic). Non-Christians cannot receive the sacraments. For a Catholic to marry a non-Catholic Christian, express permission is required from his or her bishop.
A Catholic can marry an unbaptized person, but such marriages are natural marriages only; they are not sacramental marriages. The Church, therefore, discourages them and requires a Catholic who wishes to marry an unbaptized person to receive a special dispensation from his or her bishop. Still, if the dispensation is granted, a non-sacramental marriage is valid and can take place inside of a Catholic church.
Not Too Closely Related: Legal prohibitions on marriage between cousins (and other close blood relationships, such as uncle and niece) stem from the Church's ban on such marriages. Before 1983, marriages between second cousins were prohibited—indeed, former New York mayor Rudy Giuliani received an annulment of his first marriage after determining that his wife was his second cousin. Today, second-cousin marriages are allowed, and, under some circumstances, a dispensation can be obtained to allow a first-cousin marriage. The Church still discourages such marriages, however.
Free to Marry: If one of the partners, Catholic or non-Catholic Christian, has been married before, he or she is free to marry only if his or her spouse has died or he or she has obtained a declaration of nullity from the Church. The mere fact of a divorce is not sufficient to prove the nullity of a marriage. During marriage preparation, you must inform the priest if you have been married before, even in a civil ceremony.
Of the Opposite Sex as Your Partner: Marriage, by definition, is a lifelong union between one man and one woman. The Catholic Church does not recognize, even as a civil marriage, a contracted relationship between two men or two women.
In Good Standing With the Church: It's an old joke that some Catholics only see the inside of a church when they are "carried [at Baptism], married, and buried." But marriage is a sacrament, and, for the sacrament to be properly received, the Catholic partner(s) in a marriage must be in good standing with the Church.
This means not only normal Church attendance but also avoidance of scandal. So, for instance, a couple who are living together may not be allowed to get married in the Church until they have spent sufficient time living apart. (There are exceptions—for instance, if the priest is convinced that the couple is not engaged in immoral behavior but is living together out of economic necessity.) Likewise, a Catholic politician who supports policies condemned by the Church (such as the legalization of abortion) may be denied a sacramental marriage.
When In Doubt: If you're not sure whether you are free to contract a valid marriage, or whether your potential marriage would be sacramental or non-sacramental, the first place to check is, as always, with your parish priest. In fact, if your potential spouse is not Catholic, or if either of you has been married before, you should discuss your situation with your priest even before you get engaged (if possible). And even if both of you are Catholic and free to marry, you should make an appointment with your priest as soon as possible after your engagement. Any marriage that is contracted in opposition to the regulations of the Catholic Church is not only non-sacramental but invalid.
Because of the sacramental nature of Christian marriage, and the serious nature of even non-sacramental (natural) marriage, it is not something to be entered into lightly. Your parish priest will help you ensure that your marriage will be valid—and, if contracted between two baptized Christians, sacramental.
Tomorrow, lets look at our Moslem brothers and sisters.