Can polygamy be a crime in the United States?

Here's some timely analysis by law and religion prof John Witte Jr. (It's especially timely for me because it's the subject of the Constitutional Law exam I'm working on grading right now... as I take a break to blog.)

For nearly two millennia, the Western tradition has included polygamy among the crimes that are inherently wrong. Not just because polygamy is unbiblical, unusual, unsafe, or unsavory. But also because polygamy 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 sure, but in enough cases to make the practice of polygamy too risky to condone.

Should we limit freedom to do one thing because it often leads to something else? Shouldn't we be very careful when the thing we would limit is something that we ourselves have no interest at all in doing but that other people believe is essential to their eternal salvation?

From the opinion in the 1878 Supreme Court case — Reynolds v. United States — that upheld the criminalization of polygamy:

[T]he accused, proved that, at the time of his alleged second marriage, he was, and for many years before had been, a member of the Church of Jesus Christ of Latter-Day Saints, commonly called the Mormon Church, and a believer in its doctrines; that it was an accepted doctrine of that church "that it was the duty of male members of said church, circumstances permitting, to practise polygamy; . . . that this duty was enjoined by different books which the members of said church believed to be of divine origin, and, among others, the Holy Bible, and also that the members of the church believed that the practice of polygamy was directly enjoined upon the male members thereof by the Almighty God, in a revelation to Joseph Smith, the founder and prophet of said church; that the failing or refusing to practise polygamy by such male members of said church, when circumstances would admit, would be punished, and that the penalty for such failure and refusal would be damnation in the life to come."

Reynolds was sentenced to 2 years at hard labor.

More from Witte:

[S]ome religious communities and their members might well thrive with the freedom to practice polygamy. But inevitably closed repressive regimes like the Texas ranch 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.

Why isn't it better to strictly police child abuse, rape, and under-age sex? Why pick on one sort of behavior that has a risk of leading to these things? What if the evidence showed that mothers living with men who are not their children's fathers runs a high child abuse, rape, and underage sex? Could we criminalize that too? The answer shouldn't be the religious motivation seems especially repugnant.