This week, in one of his first public statements since this past summer’s anti-gay-marriage remarks, Chick-fil-A President Dan Cathy told an Atlanta television reporter that he supports “Biblical families.” This comment immediately gave rise to jokes questioning his familiarity with the Old Testament, where, as any Mormon elder can tell you, patriarchs such as Abraham, Jacob and David all practiced polygamy.

John Witte Jr., however, thinks it isn’t so funny. A scholar of religion and law at Emory University in Atlanta, Witte is working on a lengthy history of polygamy due out next year. He believes that polygamy is the next frontier in marriage and family law. If states are able to dismantle traditional or conventional views of marriage by allowing two men or two women to wed, then why should they not go further and sanction, or at least decriminalize, marriages between one man and several women?

This is the argument that Kody Brown and his wives, the stars of the reality television show “Sister Wives,” are making in a civil suit against the state of Utah. They are claiming that Utah’s anti-polygamy laws violate their privacy and their religious freedom. “The Browns want to be allowed to create a loving family according to the values of their faith,” Jonathan Turley, the family’s lawyer, wrote in an op-ed this summer.

Beneath the sensationalism, there lies a real question. If Americans increasingly value their rights to privacy and liberty above historical social norms, then why should the state not legally approve other unconventional domestic set-ups? In his first chapter, Witte presents the problem this way. “After all,” he writes, “American states today, viewed together, already offer several models of state-sanctioned domestic life for their citizens: straight and gay marriage, contract and covenant marriage, civil union and domestic partnership. Each of these off-the-rack models of domestic life has built-in rights and duties that the parties have to each other and their children and other dependents. And the parties can further tailor these built-in rights and duties through private prenuptial contracts. With so much marital pluralism and private ordering already available, why not add a further option — that of polygamous marriage?”

This is an argument that makes defenders of individual liberties sweat, for few people like to be put in the spot of having to uphold a social taboo. But really. If the purpose of marriage is to preserve personal happiness, protect and raise children, and create social stability through shared property and mutual obligation, then why is polygamy so problematic if it occurs among consenting adults? The two-parent household may be an ideal, but real life is far messier than that. Children are raised all the time by groups of adults: there are exes and steps, adoptive parents and biological, mistresses and wives. Didn’t someone say it takes a village?

The sister wives share a hug. L to R: Meri, Christine, Janelle, Robyn. (Bryant Livingston/TLC)

Witte is worried about this line of thinking. He sees the “sexual liberty for all” folks increasingly pressing their cases in law reviews, saying “those that oppose polygamy are just like the homophobes and the patriarchs.”

In British Columbia last year, under pressure from pro-polygamy groups — who tend to be on the far right and the far left of the political spectrum — the Supreme Court heard arguments for and against upholding the province’s anti-polygamy laws. The court upheld them.

And in real life, the cases keep on coming. Kody Brown is an attention seeker, but other people are living nice, quiet lives with their multiple, simultaneous partners. In 2006, a longtime judge named Walter Steed was forced to resign from the bench in Hildale, Utah, after an anti-polygamy group made public his domestic situation. Steed had legally married his first wife, Jessica, in 1965, and subsequently “spiritually” married two of her sisters, Marilyn, in 1975, and Viola, in 1985. All were adults, and together, they had 32 children. “He was a nice guy, always cooperative. He was never deceptive or deceitful about what his status was,” a court administrator told the Salt Lake Tribune.

Various religious sects — not just members of breakaway Mormon groups but also some fundamentalist Muslims, some Hmong and in England a threesome who worship the Norse gods — practice polygamy. Are they not entitled to freely practice their religion?

Witte says no. Same-sex marriage does not open the door to polygamy because what matters in marriage is not who but how many. According to his research of civil law and religious tradition, the meaningful number is two. Polygamy creates competition and rivalries; it can foster insularity and religious zealotry; at its worst, it can subordinate women and children. Two has moral resonance, for it forces a couple to seriously consider their vows “for better and worse;” it shows children an example of mutual love and respect.

Witte is content to let people have sex with however many people they want. But in marriage, he says, the state must insist that it knows best. In a wedded union, three is a crowd.

To read Lisa Miller’s previous columns, go to onfaith.