A long stride towards full multiculturalism in Europe is about to be taken in Germany. By decision of its federal parliament, religious marriages will no longer need to be twinned with register office ceremonies. So far no religious ceremony could take place without a prior register office wedding. From January 1, 2009 that requirement is scrapped.

This must make Otto von Bismarck, the secular chancellor of the drooping moustache and iron determination, turn somersaults in his north German grave. For it makes decisive inroads into the secular state that he above all secured for Germany. In this, the State was given primacy in matters of personal status, and the Catholic and Protestant Churches, and all other religious institutions, were relegated to a secondary role.

Their absolute right to conduct life-cycle ceremonies — baptism for Christians, circumcision for Jews and Muslims, marriage ceremonies and funeral rites — remained. But the State claimed primacy in dictating the legal framework and the legal implications.

Civil law determined the status of the individual, and the validity of baptism or any other religious ceremony was strictly confined to the religious community under whose auspices they took place. And marriage, the life-cycle event whose importance is exceeded only by birth and death, was placed firmly within the authority of the State. The federal parliament decides its legal framework, amends the laws of marriage and divorce as it thinks fit, and always according to mostly secular norms.

The French Revolution of l789 toppled not only the Bourbon monarchy but also curbed the power of the Pope and all churches irrevocably, ultimately throughout most of Europe. Their writ now rules within limitations imposed by the State.

The legal clarity which that created for every individual within the State has now been clouded. And because multiculturalism is now the dominant ideology in Europe, as it is in Britain, its extensions in one country are liable to prove infectious throughout the Continent.

The core of the problem lies in the nature of marriage. For it is paradoxical. It starts with the most private of all human relationships, the sexual expression of human love. But the moment the couple declare this love publicly and twin this declaration with a wish, implied or expressed, for permanency, it becomes public. For they become a new unit in the structure of our society. “It enriches society and strengthens community,” as the latest Church of England rite puts it.

That marriage is not, and never has been, a private matter is underlined by the need for two witnesses. Judaism, for instance, goes the extra furlong to ensure the independence of those witnesses. It insists that neither may be related to one or other of the partners who are about to enter the marriage.

The precedent now set by the Federal German Parliament has pitfalls the size of canyons. For the principle it has now, intentionally or otherwise, established is that within one state there can be two rival systems of law. And that is capable of multiple extensions.

From personal status, it could extend into contractual relationships, into the relationship between employers and their hired help, into the commercial dealings of shopkeeper and customer. Jewish religious law, and the courts that apply this, called Batei Din, embraces all these areas. But appearance before and submission to the Batei Din are voluntary. And other than seeking to ban offenders from participation in synagogue life — and even that sanction is subject to the final authority of the lay leadership — these religious courts have no power of enforcement.

Parliament and the civil courts reign supreme over Jewish communal life, even though that is mostly religious. And for the past 1,938 years, since Jewish dispersion began after the destruction of the Temple in Jerusalem in AD 70, Jewish canon law, or Halachah, has expressly recognised this.

The Talmud proclaimed that the law of the kingdom in which Jews happen to reside is the law. And especially in matters of status, civil law takes precedence over Jewish religious law and custom. Hence in congregations belonging to Britain’s main synagogal bodies, marriages are not performed except under parliamentary licence or after a register office ceremony has already taken place.

And because polygamy faded from early medieval society in Europe, it equally faded from the Jewish communities in France and Germany, some of which trace their history back to the 5th and 6th centuries. Although polygamy was formally forbidden to European Jews only around the year 1000, Jewish society had already adapted to its surroundings in this vital area of civil law and practice centuries earlier. From the earliest years of their diaspora Jews realised that they could not live under two competing systems of law. One of the two systems, that of Halachah and that of the country in which they lived, supremacy had to go to the law of the land.

This is the challenge that now faces the 3,749,000 Muslims living in Germany. They, too, acknowledge two competing systems of law, Sharia administered by their imams and the law administered by the civil and criminal courts of the land.

The German State will see to it that, especially in criminal cases, German law prevails. But the imams have yet to acknowledge that their rules take second place. The alternative is chaos, which no modern civil society can tolerate.

So the big step forward now taken by multiculturalism across the Channel deserves the plaudits of every pluralist. But viewed from the perspective of European Jewish history, it should also be a matter of deep concern for everyone who has the legal protection of those entering marriage at heart. For without a clear acknowledgement by Germany’s imams of the supremacy of that country’s civil law, this triumph of multiculturalism could trigger chaos and tragedy for all Muslim brides and their grooms.

William Wolff is area rabbi for northeastern Germany, based in Schwerin