With the activist judge Walker’s overruling of Prop. 8 in California, the debate over the definition of “marriage” once again rages on. Yet, the same reason that women cannot be priests is the reason why same sex couples cannot be married. St. Paul touches on this in Ephesians 5 when he discusses the roles of a husband and wife in relation to each other. He concludes by quoting Genesis 2:24:
"For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh."
He then adds:
“This mystery is a profound one, and I am saying that it refers to Christ and the church.”
So how does what St. Paul says here in Ephesians 5 exclude women from the priesthood and same sex couples from marriage? Because St. Paul informs us that the mystery of marriage refers to Christ and the Church. This means that the imagery of Christ in relation to the Church is not modeled on the human institution of marriage, but vice versa! From all eternity it was in the will of God that Christ, the Bridegroom, should be united to His Bride, the Church. From all eternity there was intended a complementarity of the masculine with the feminine. This eternal nuptial between Christ and His Bride is what marriage is modeled upon. Therefore, any talk of marriage being between a man and a man or a woman and a woman is nonsense. There is no complementarity between two of the same sex, so no matter what one wishes to call it, it will never be a marriage.
But how does Ephesians 5 exclude women from the priesthood? Precisely because a priest acts in persona Christi, in the person of Christ. Christ as a person on earth was/is a man. And as Christ is married to His Bride, the Church, so too, a man who is ordained as a priest has the Church for His Bride (consequently, this is also an argument for the celibate priesthood, since Christ was not a polygamist, neither should a priest be by having two wives; earthly and heavenly). Now if a woman were to be a priest, there would be two feminine elements instead of the complementarity of masculine and feminine. As explained above, this cannot happen.