20 Next, the dignity of the sacrament must be considered, for through addition of the sacrament the marriages of Christians have become far the noblest of all matrimonial unions. But to decree and ordain concerning the sacrament is, by the will of Christ Himself, so much a part of the power and duty of the Church that it is plainly absurd to maintain that even the very smallest fraction of such power has been transferred to the civil ruler.
Source: Arcanum Divinae (Vatican.va)