Marquart, from *The Church* p. 161, 162. He is speaking about the statement of the Augsburg Confession that our churches teach that no one is to preach, teach, or administer the sacraments without a regular call, or being called according to rite (i.e., called and ordained):
First of all it is necessary to understand that it is not here a question of "cannot" - in a sacerdotalist sense - but of "may not," in the sense of the divinely established evangelical order in the church. It is an evangelical axiom that the ministry derives its validity from the Gospel, and not vice versa (Phil. 1:15-18). The minister therefore does not "make" the sacrament by some occult powers inhering in his person or office, as distinct from the rest of the people of God. Rather, as his title, "minister," indicates, he merely serves Christ and His people by "administering" the sacraments Christ Himself makes through the continuing efficacy of His words of institution. The minister's function is strictly instrumental: "The person adds nothing to this Word and office commanded by Christ" (Tr. 26, German). Or, in Luther's famous remark of 1533:
For our faith and the sacrament must not be based on the person, whether he is godly or evil, consecrated or unconsecrated, called or an impostor, whether he is the devil or his mother, but upon Christ, upon his word, upon his office, upon his command and ordinance. (AE 38:200)
So long as Christ's words of institution are allowed to stand unperverted (see FC SD VII,32), the means of grace retain their own inherent validity and efficacy. Thus even where, as in the case of women, purported ordinations are null and void, because they are contrary to God's Word, sacraments celebrated by such persons are not to be regarded as invalid per se, but as disorderly and schismatic, that is, as having been done by private, uncalled persons.