If that were the case, the US would have to recognize Islamic polygamous marriages. It doesn't, so it isn't.
That doesn't mean the unelected liberal SCOTUS superlegislature won't step in to give us a boost down the road to hell by sanctifying perversion in the name of marriage.
I honestly have no idea.
Are all of the kids labeled bastards?
Is only the first wife entitled to benefits?
Can the man, and his "other" wifes, be charged with adultury or polygamy?
What happened to the Mormons with nine wifes, when it became illegal to have more than one?
I would really like to know...