The Lutheran tradition, from 1517 forward, developed a social model of marriage, grounded in Martin Luther's doctrine of the heavenly and earthly kingdoms. Marriage, Luther and his colleagues taught, was a social estate of the earthly kingdom of creation, not a sacred estate of the heavenly kingdom of redemption. Though divinely ordained, marriage was directed primarily to human ends, to the fulfilling of civil and spiritual uses in the lives of the individual and of society. Marriage revealed to persons their sin and their need for God's marital gift. It restricted prostitution, promiscuity, and other public sexual sins. It taught love, restraint, and other public virtues. Any fit man and woman were free to enter such unions, clerical and lay alike. Indeed, all persons were encouraged to marry when they came of age, unless they had the rare gift of continence. This was especially imperative for Christian clergy, for a pastor's experience of marriage would enhance his pastoral ministry to the married, and his marital parsonage would serve a model for proper Christian living in the community.
As part of the earthly kingdom, Lutheran reformers argued, marriage was subject to the civil law of the state, not to the canon law of the church. To be sure, marriage was still subject to God's law, but this law was now to be administered by Christian magistrates who were God's vice-regents in the earthly kingdom. Church officials were required to counsel the magistrate about God's law and to cooperate with him in publicizing and disciplining marriage. All church members, as part of the priesthood of believers, were required to counsel those who contemplated marriage, to admonish those who sought annulment or divorce, and to aid in the rearing of all children as their collective baptismal vows prescribed. But principal legal authority over marriage and family life lay with the state, not with the church.
This new social model of marriage was reflected in the transformation of marriage law in Germany and other Lutheran polities of Western Europe. Civil marriage courts replaced church courts. New civil marriage statutes replaced traditional canon law rules. Lutheran jurists published scores of treatises on marriage law, affirming and embellishing the new Lutheran theology of marriage. The new Lutheran marriage law, like the new Lutheran marriage theology, remained indebted to the Catholic canon law tradition. Traditional marriage laws, like prohibitions against unnatural sexual relations and against infringement of marital functions, remained in effect. Impediments that protected free consent, that implemented biblical prohibitions against marriage of relatives, and that governed the couple's physical relations were largely retained. Such laws were as consistent with the Catholic sacramental model as with the Lutheran social model of marriage.
But changes in marriage theology also yielded changes in marriage law. Because the Lutheran reformers rejected the subordination of marriage to celibacy, they rejected laws that forbade clerical and monastic marriage, that denied remarriage to those who had married a cleric or monastic, and that permitted vows of chastity to annul promises of marriage. Because they rejected the sacramental nature of marriage, the reformers rejected impediments of crime and heresy and prohibitions against divorce in the modern sense. Marriage was for them the community of the couple in the present, not their sacramental union in the life to come. Where that community was broken, for one of a number of specific reasons (such as adultery or desertion), the couple could sue for divorce and the right to remarry. Because persons by their lustful nature were in need of God's remedy of marriage, the reformers removed numerous impediments to marriage not countenanced by Scripture. Because of their emphasis on the Godly responsibility of the prince, the pedagogical role of the church and the family, and the priestly calling of all believers, the reformers insisted that both marriage and divorce be public. The validity of marriage promises depended upon parental consent, witnesses, church consecration and registration, and priestly instruction. Couples who wished to divorce had to announce their intentions in the church and community and to petition a civil judge to dissolve the bond.