Q&A: The Minister of the Sacrament of Matrimony
Q. How is it possible that the spouses are the ministers of the sacrament of matrimony in the Latin Church, while the priest is the minister in the Eastern Churches?
A. This is a common misunderstanding, but the answer is that this is simply not the case. There cannot be a substantial difference in sacramental theology between the Latin and Eastern Catholic Churches, because if they are to remain in communion with one another, they must share the same faith, sacraments, and ecclesiastical governance. Regardless of which Church sui iuris the spouses belong to or what rite is being employed in the marriage ceremony, it is theologically certain that the contracting parties are the ministers of the sacrament to each other, because the essence of marriage lies exclusively in the contract.
The proposition matrimonium facit consensus—which means that marriage is contracted through mutual, expressed consent—has been upheld by the Church since antiquity. Implicit in this ancient maxim is the belief that the persons contracting marriage are themselves the ministers of the sacrament. There were no serious attempts to challenge this point until the sixteenth century, when Melchior Canus argued in De locis theologicis that it is a mere theological opinion, and not a settled matter, that a valid marriage can take place without a priest. Regarding the marriage contract as the matter and the priestly blessing the form, he himself opines that in such a case, the sacramental form would be missing, and therefore, there is no sacrament. However, it would be erroneous to separate the marriage contract from the sacrament, because it is theologically certain that every marriage contracted between baptized persons is itself a sacrament.
A few centuries later, Gallicanic and Josephinic theologians argued that the contract was simply a precondition of the sacrament, with the priestly blessing being the exclusive outward sign. The purpose of this was to separate the contract from the sacrament, thus promoting civil marriage, as the State would now have jurisdiction over the contract, and the Church over the sacrament alone. A similar idea then took root in the East: in the nineteenth century, the Greek Orthodox adopted the view that consent is the matter of the sacrament, while the prayer and blessing of the priest is the form, thus making the priest the minister. In the twentieth century, the Russian Orthodox took this further and proposed that the entire sacramental sign consisted of the religious rite performed by the priest . As for the current misunderstanding in the Eastern Catholic Churches, this likely arose from an infiltration of Orthodox ideas after the Second Vatican Council as a result of false ecumenism, the same false ecumenism that currently compels some theologians to refer to schismatic sects as “sister Churches”.
Although the Church has always detested clandestine marriages and condemned those who contract marriage without her blessing, the sacramental character of marriage was not denied in those cases. However, at the Council of Trent, it was decided to impose canonical form for the validity of marriage in areas where clandestine marriages were known to be a widespread issue, so that it would not be possible for two people to exchange consent privately and then to deny that it had ever happened. In the centuries that followed, the scope of canonical form was extended beyond its original formulation, to the point where it is universally imposed for validity in both the East and the West today. Canonical form should not be confused with the sacramental form of marriage itself, as it is clearly an institution of the Church and not essential to the sacrament.
According to the 1990 Code of Canons for the Eastern Churches, when celebrating marriage in an Eastern rite, the priest who receives the consent of the contracting parties in the name of the Church must have the “faculty of blessing the marriage” (c. 828 §1). The concept of “faculties” refers to jurisdiction, not the power of orders, and thus, the priest is performing a juridic act, not conferring a sacrament. Therefore, it can be logically concluded that the blessing is part of canonical form, rather than the conferral of the sacrament itself—in fact, this canon is the first under the heading “The Form for the Celebration of Marriage”, which explicitly discusses canonical form. Dispensations from canonical form may be given for a grave reason (c. 835), and marriages can be contracted without the presence of a priest in a case of necessity (c. 832), which further demonstrates that the priestly blessing is not essential to the sacrament itself, and that a valid marriage can be contracted without a priest.
While many have misinterpreted the priestly blessing, or “crowning” ceremony, in the Eastern rites as evidence that the priest is the minister of the sacrament in the East, this is simply false: there is no difference in sacramental theology on this point, but only a relatively minor difference in canon law.
 Ludwig Ott, Fundamentals of Catholic Dogma. Charlotte, NC: TAN Books, 1974, p. 466.