Much of the opposition of late in the United States to gay marriage is based on the bible. I wrote extensively in the past on my issue with people using the Bible to promote hatred. I came across an interesting site which points out some other Biblical rules to add to the Bill of Rights if lawmakers are to be consistent.
Marriage shall not impede a man's right to take concubines in addition to his wife or wives. (II Sam 5:13; I Kings 11:3; II Chron 11:21)
A marriage shall be considered valid only if the wife is a virgin. If the wife is not a virgin, she shall be executed. (Deut 22:13-21)
There are several others.