C.S. Lewis writes, in Mere Christianity:
A great many people seem to think that if you are a Christian yourself you should try to make divorce difficult for every one. I do not think that. At least I know I should be very angry if the Mohammedans tried to prevent the rest of us from drinking wine.
My own view is that the Churches should frankly recognise that the majority of the British people are not Christians and, therefore, cannot be expected to live Christian lives.
He goes on to say:
There ought to be two distinct kinds of marriage: one governed by the State with rules enforced on all citizens, and the other governed by the Church with rules enforced by her on her own members. The distinction ought be to quite sharp, so that a man know which couples are married in a Christian sense and which are not.
Andrew Sullivan has more thoughts on this.