I’m not planning on talking about politics much on this blog, but the relationship between the United States government (including state laws) and marriage is very odd, in a way I haven’t seen discussed very often.
The First Amendment restricts the United States government, as well as all the states, from either supporting or discriminating against any religion. Therefore, according to the Constitution, any legal establishment of “marriage” must be secular. Legally, laws talking about marriage and religions talking about marriage are talking about two entirely separate things; Christian marriage, or Muslim marriage, or any other religious marriage cannot be addressed by any law in the United States.
Any arguments against legalizing gay marriage, or polygamy, or any other marriage practices, that is based on religion, thus, is completely irrelevant to the laws of the United States.
The U.S. can, of course, still create a legal concept of marriage, which in recent times has come under legal challenges. But it’s important to note that that any discussion of religion is probably misplaced when talking about the legality of marriage in the United States; the U.S. is not allowed to “protect” any form of religious marriage.