From New Advent:
Though ecclesiastical law does not affect the acts of infidels as such, yet the Church has to pass judgment on the validity of these acts and their juridical consequences when infidels come within the fold by baptism. No act of an infidel can have any value from the point of view of the spiritual society to which he does not belong; he is incapable by Divine law of receiving the sacraments, notably Holy orders (evidently we are not speaking here of a purely material reception); nor can he receive or exercise any ecclesiastical jurisdiction. The acts of infidels are to be considered in the light of natural law, to which they, like all men, are subject, and in accordance with the Divine law, in so far as it determines the secondary natural law. This applies principally to the case of matrimony. The marriage of infidels is valid as a contract under natural law, not as a sacrament, though at times this word has been applied to it (cf. Encycl. Arcanum); it is subject only to the impediments of natural law and, at times, to those of the civil law also, but it is not affected by the impediments of canon law. However the Church does not recognize polygamy as lawful among infidels; as to divorce strictly so called, it admits it only under the form of the Casus Apostoli, also known as the privilege of the Faith or the Pauline privilege; this consists in a convert being permitted to abandon his partner, who remains an infidel, if the latter refuse to continue the common life without endangering the faith of the convert (cf. DIVORCE, I, B, 1); under such circumstances the convert may marry a Catholic. As to acts which are prohibited or void in virtue of canon law alone, they are valid when performed by infidels; thus, the impediment of the remoter degrees of consanguinity and affinity, etc., does not affect the marriages of infidels. But the juridical consequences of the acts, performed by them when infidels, begin to exist at the moment of and in virtue of their baptism; consequently, a converted widower may not marry a relative of his late wife without dispensation; and again, a man who has had two wives before his conversion is a bigamist and therefore irregular.
In this place mention may be made of the ecclesiastical law forbidding the faithful to marry infidels, a prohibition which is now a diriment impediment, rendering a marriage null and void unless a dispensation has been obtained (see DISPARITY OF WORSHIP). It is easy to see that there is a real danger to the faith and religious life of the Catholic party in the intimacy of married life and in the difficulties in the way of a Christian education of the children; and, if that party be the wife, in the excessive authority of the husband and the inferior condition of the wife in infidel countries; consequently, this dispensation is granted only with difficulty and when the precautions dictated by prudence have been taken. The laws regulating the dealings between Catholics and infidels in civil life were inspired also by religious motives, the danger of perversion, and the high idea entertained in the ages of faith of the superiority of Christians to infidels. These regulations, of course, did not refer to all acts of civil life; moreover, they were not directed against all infidels indifferently, but only against Jews; at the present day they have fallen almost completely into desuetude. In the early Middle Ages, Jews were forbidden to have Christian slaves; the laws of the decretals forbade Christians to enter the service of Jews, or Christian women to act as their nurses or midwives; moreover, Christians when ill were not to have recourse to Jewish physicians. These measures may be useful in certain countries today and we find them renewed, at least as recommendations, by recent councils (Council of Gran, in 1858; Prague, in 1860; and Utrecht, in 1865). As for the Jews, they were ordinarily restricted to certain definite quarters of the towns into which they were admitted, and had to wear a dress by which they might be recognized. Modern legislation has given the Jews the same rights as other citizens and the intercourse between them and Catholics in civil life is no longer governed by ecclesiastical law. (See JEWS AND JUDAISM; MOHAMMED AND MOHAMMEDANISM.)
