[Catholic Church] According to Catholic canon law, the fundamental idea of an impediment to matrimony is contained implicitly in the prohibitions of Leviticus and some ancient canonical texts; in the latter may be discovered the basis of the celebrated distinction between diriment impediments which render a marriage null and void, and prohibitory impediments which only render it illicit.
Prohibitory impediments include:
1. Prior betrothal, whereby any other marriage would be a violation of that right.
2. Conflicting vow, namely a vow of chastity.
3. Mixed marriage, namely with a non-baptized Catholic.
4. Vetitum Ecclesio, namely a veto by a bishop.
5. Forbidden times for marriage, namely from Advent to the Epiphany, and from Ash Wednesday to Low Sunday.
Diriment impediments, namely those that render marriage null and void, include:
1. Impediments arising from: the physical incapacity of the subject (impuberty and impotency); presumption of want of consent, abduction, namely the incapacity of the abductor of contracting valid marriage with the woman whom he has abducted, until she has first been allowed to go free; disparity of worship renders void the marriage of a Christian with an infidel, that is, of a baptized person with one who is unbaptized; prior marriage, namely in the case of a previous matrimonial engagement whereby any marriage of a married person was rendered void during the lifetime of the person to whom he or she has been validly married; prior relationship, namely: natural relationship or community of blood to the fourth degree or generation; an alliance which establishes a bond of relationship between each of the married parties and the blood relations of the other, and forbids marriage between them to the fourth degree; public decorum, a legal anticipation of affinity; spiritual relationship, prohibiting marriage between those taking an active part in the rites of Christian initiation, baptism, and confirmation; arising from the legal relationship of adoption.
3. Defect of consent insanity or total ignorance, or error.