You make a good point about "Biblical" authority for deciding such matters. As with most major religions, or political philosophies for that matter, one notices a tendency for practitioners to be highly selective, to say the least, about what parts of their source literature are valid or not. A cover-to-cover reading of the Bible, particularly the Old Testament, would curl your hair. God apparently used to be one bad mutha before, like many others, he mellowed out when he had a kid. ;)

On the other hand, the concept of marriage, i.e. a formalized permanent relationship between a man and a woman, long predates the Bible, crosses many widely-varied cultures, and is not something that should be easily tossed aside or redefined on a whim. It's there for a reason, or it would not be so far-reaching. My definition of marriage is also limited to a man and a woman.

On the gripping hand, like an immense number of other things I could name where Washington sticks its large nose into our business, this is not something the Federal government should be dealing with, and it is certainly not something that should be handled with a Constitutional amendment.

Fortunately, it's damn hard to amend the Constitution, something that has saved our bacon more than once.