Marriage Impediments

A couple that wants to marry should make known their intention of contraction marriage several weeks before the date set for their marriage. That way time is left for objections to be made - if there are reasons why the marriage cannot take place.
This article is about under what circumstances a marriage is forbidden by the Catholic Church; some reasons are in themselves sufficient to invalidate it altogether, others do not absolutely prevent the possibility of marriage, but render it undesirable and harmful.

Nullifying impediments of marriage are: 

• Lack of proper age;
• Certain physical defects, like impotency;
• The bond of a previous marriage; exceptions are the dissolution of a non-consummated marriage by Papal dispensation, or dissolution of marriage of two persons not baptized at the time the marriage occurred;
• Holy Orders;
• Solemn vows;
• Abduction;  if a man compels a woman to marry him, threatening to kill her in case of refusal, or to do her some very serious injury, their marriage is not valid; her consent is extorted by force, and is not given voluntarily;
• Crime, like causing the death of a partner by mutual cooperation, either physical or moral;
• Blood relationship to all in the direct line, and to the third degree in the collateral line;
• Affinity or relationship through marriage to all in the direct line, and to the second degree in the collateral line;
• Mistaken identity, when there is a mistake as to one of the contracting parties;
• Spiritual relationship, which exists between a baptized person, and the one who baptized him, or stood for him in Baptism;
• Legal adoption; wherever it is an impediment under the civil law. 

Besides the above mentioned impediments there are certain ones which - though they do not nullify marriage - yet render it undesirable.  

These prohibitive impediments are:

• Certain simple vows, like a vow not to marry, or a vow of virginity and perfect chastity;
• Legal adoption whenever it is a prohibitory impediment under civil law;
• Mixed marriages (“disparity of worship”): the Catholic Church also forbids marriage with fallen-away Catholics, public sinners, excommunicated persons, etc. Mixed marriages are allowed by the Church only for weighty reasons, and when sufficient safeguards are given in behalf of the Catholic party and the religion of the children.

The Protestants and the Roman Catholic Church differ over what would constitute an impediment to marriage. The Church of England, for example, recognizes remarriage after divorce in some circumstances.

The Catholic Church regards marriage as an unbreakable contract. Divorce is not permitted unless there is some canonical impediment to the earlier marriage. In this situation, an annulment may be granted. In the Protestant Church marriage is a contract, but is not unbreakable. Divorce is discouraged, but permitted as evidence of human weakness. 

In the Netherlands and Belgium, there is a statutory requirement - for couples intending to marry - to formally register that intention with officials, beforehand. Civil marriage is mandatory, but people can also have a religious ceremony. For remarriage one needs a marriage certificate in the case of a previous marriage, a divorce decree in the case of a previous divorce, or a death certificate in the case of being widowed.

Source: CatholicHarborOfFaithAndMorals.com
Further Reading: Marital Dispensations, Consanguinity, Affinity.