"marriage laws are very recent in historical terms. Barely a couple hundred years old in Europe and British North America."

They might be new in secular terms. In religious or canon law they go back a long way. Henry VIII had his problems nearly five centuries ago. Don't even think about Ruth and Boaz.

Kerry's problem appears to be that facing most Catholics - those in Rome want power over the individual conscience. If I understand my history fully, this was one of Luther's complaints. I would have to say that the current church hierarchy have more justfication for their actions than those of the 15th and 16th centuries.