Charles J. Callan, Moral Theology
“ A purely civil marriage between Catholics is invalid, as far as the bond is concerned, since their contract, as being a Sacrament, is subject to the Church. But the civil marriage, as far as the purely civil consequences are concerned, is a lawful ceremony, and is obligatory if required by law. A morganatic marriage is made between two persons of unequal condition (e.g., between a king and a plebeian woman) on condition that the inferior spouse and progeny shall not share entirely in the titles and property of the superior spouse. ”
