Legal exegesis: marriage, same-sex marriage, and polygamy

I love reading about the law, as often legal questions are questions of exegesis. The meaning of terms, authorial intent, and a host of other issues are at stake. One such example is Kody Brown and his challenge to Utah laws against polygamy. (I learned about this from this New York Times piece.) This is a challenging read because of all of the legal angles in question at the same time. Suffice it to say that you have to think very clearly and carefully to follow the points being made, especially in the counterpoint which defends same-sex marriage. The nutshell summary is that Brown wishes to defend his polygamy on the grounds that it's not really polygamy. He is only legally married in the state of Utah to one of his wives, while the other women are "sister wives," a category recognized by his offshoot branch of Mormonism. Thus it is a question of religious freedom. I believe this particular question of polygamy and most if not all the cultural questions surrounding marriage can be solved on a legal basis, not even to speak of a biblical one, by examining the issue of authorial intent: It is inconceivable to me that the original authors of marriage laws ever thought of anything other than the traditional understanding of a single man and single woman joining themselves together in social, cultural, legal union exclusive of any other individuals or entities. The constant redefinition taking place at present in our society amounts to an exegetical sleight of hand which ignores authorial intent on a fundamental level.