...is the lifelong union of a man and a woman. The Church knows that marriage between baptised Christians is a sacrament - Holy Matrimony - a source of grace, a rich and living reality linked to Christ's union with his Church, a mystery at the heart of our Faith.
If the Government wants to impose on Britain the notion of marriage as a union between two people of the same sex, it is going to be neccesary to explain that there can be no question of this ever involving any sort of event or ceremony linked to the Church. The most efficient way to do this would be simply to break the link of the Church with any form of legal marriage: the Sacrament of Holy Matrimony in Church would be unconnected with any civil ceremony taking place in a local registry office. A Catholic man and woman marrying in church might or might not choose to go through a legal ceremony too: as far as the Church is concerned, only the Church's sacramental marriage is valid anyway.
Until now, the Church has sought to co-operate with the civil authorities because it makes sense for the Church to act as legal registrar for marriages that take place in church. But this will change if the civil authorities redefine marriage.
There are a number of practical advantages in simply de-registering churches, and it will of course also save the clergy the bother of extra paperwork. The Church's own paperwork already neccesarily keeps them busy: each bride and groom have to show evidence of baptism, of being free to marry (ie not married already, not under a vow of celibacy etc), and so on.
In the past, some people sought to marry in church who were not eligible to do so - eg people who were divorced and whose previous spouse was still living. But when the Church gently explained that this was not possible, they did not sue. Under planned legislation, and in the current climate, the Church could be vulnerable to legal challenges unless it is made clear that there can never be any offer of any form of legal marriage in a Catholic church, and that all that the Church can offer is Holy Matrimony, on the terms God offers.
A Church-married-but-not-state-married couple might feedl they had some legal need to consolidate their status by going through a legal procedure, eg for tax purposes, and the Church would not prevent them from doing this. If they wanted to divorce, that would not alter their being married in the eyes of God. With today's divorce practices, which are often unjust (fathers denied the right to see their children, etc) , the Church does well to remain unconnected with the tangles of it all.
Freedom for the Church is going to be a major issue in the years ahead, both in Britain and in other Western nations. For a useful comment on the position in the USA, read here.