A century and a half ago, Mormons made national headlines by claiming a First Amendment right to practice polygamy, despite criminal laws against it. In four cases from 1879 to 1890, the United States Supreme Court firmly rejected their claim, and threatened to dissolve the Mormon church if they persisted. Part of the Court's argument was historical: the common law has always defined marriage as monogamous, and to change those rules "would be a return to barbarism." Part of the argument was prudential: religious liberty can never become a license to violate general criminal laws "lest chaos ensue." And part of the argument was sociological: monogamous marriage "is the cornerstone of civilization," and it cannot be moved without upending our whole culture. These old cases are still the law of the land, and most Mormons renounced polygamy after 1890.

The question of religious polygamy is back in the headlines – this time involving a fundamentalist Mormon group on a Texas ranch that has retained the church's traditional polygamist practices. Many of the legal questions raised since this group was raided are easy. Under-aged and coerced marriages, statutory rape, and child abuse are all serious crimes. Those adults on the ranch who have committed these crimes, or intentionally aided and abetted them, are going to jail. They have no claim of religious freedom that will excuse them, and no claim of privacy that will protect them. Dealing with the children, ensuring proper procedures, and sorting out the evidence are all practically messy and emotionally trying questions, but not legally hard.

The harder legal question is whether criminalizing polygamy is still constitutional. Texas and every other state still have these laws on these books. Can these criminal laws withstand a challenge that they violate an individual's constitutional rights to private liberty, equal protection, and religious liberty? In the nineteenth century, none of these rights claims was available. Now they protect every adult's rights to consensual sex, marriage, procreation, contraception, cohabitation, sodomy, and more. May a state prohibit polygamists from these same rights, particularly if they are inspired by authentic religious convictions? What rationales for criminalizing polygamy are so compelling that they can overcome these strong constitutional objections?

Theologians often cite the Bible which says that "two" – not three or four – parties must join in "one flesh" to form a marriage. Others remind us that early biblical polygamists did not fare well. Think of the problems confronted by Abraham with Sarah and Hagar, or by Jacob with Rachel and Leah. Or think of King Solomon with his thousand wives; their children ended up killing each other. This may be a strong foundation for a church or synagogue to prohibit polygamy among its voluntary members, but can such biblical arguments prevail in a pluralistic nation that prohibits the establishment of religion?

Child experts raise serious concerns about the development of children of polygamy. Won't these children be confused by mixed parental signals and attachments, and by inevitable rivalries with their half siblings? And won't they be stigmatized by their peers? These arguments have some bite. But how different is the polygamous lifestyle in our current pluralistic culture? Children are raised by live-in grandparents, nannies, and day care centers. They live in large blended families and boarding schools. Their parents may be gay and lesbian couples, or their families may have religious dress codes that set them apart from their peers. Are children of polygamy so differently positioned?

The strongest argument against polygamy is the argument from moral repugnance. Polygamy is inherently wrong – "just gross" as my law students say, "malum in se" as we law professors put it. Many states legislate against a lot of activities – slavery, indentured servitude, gambling, prostitution, obscenity, bestiality, incest, sex with minors, self-mutilation, organ-selling, and more – just because those activities are wrong or they inevitably foster wrongdoing. That someone wants to engage in these activities voluntarily for reasons of religion, bravery, custom, or autonomy makes no difference. That other cultures past and present allow such activities also makes no difference. For nearly two millennia, the Western tradition has included polygamy among the crimes that are inherently wrong – not just because polygamy is unbiblical or unsavory, but also because it routinizes patriarchy, jeopardizes consent, fractures fidelity, divides loyalty, dilutes devotion, fosters inequity, promotes rivalry, foments lust, condones adultery, confuses children, and more. Not in every case, to be su re, but in enough cases to make the practice of polygamy too risky to condone.

Furthermore, allowing religious polygamy as an exception to the rules will make some churches and mosques a law unto themselves. Again, some religious communities and their members might well thrive with the freedom to practice polygamy. But inevitably, closed and repressive regimes like the Texas compound will also emerge – with under-aged girls duped or coerced into sex and marriages with older men, with women and children trapped in sectarian communities with no realistic access to help or protection from the state and no real legal recourse against a church or mosque that is just following its own rules. We prize liberty, equality, and consent in this country too highly to court such a risk. If you're not sure, just ask some of those moms and kids on the Texas ranch.

John Witte, Jr. is Director of the Center for the Study of Law and Religion at Emory University in Atlanta.