There has been some discussion (e.g., here and here) about whether the Supreme Court's June 26 decision in Obergefell v. Hodges legalizing gay marriage portends the future legalization of polygamy in the United States.

The majority opinion, by Justice Anthony Kennedy, does not mention polygamy and its language appears to favor monogamy. It cites four principles: the right to marry as supporting "a two-person union unlike any other in its importance to the committed individuals," personal choice in marriage as an aspect of liberty, marriage as a safeguard for children and families, and marriage as a keystone of our social order. It concludes that both Due Process and Equal Protection require extending the same marriage dignity to homosexual as to heterosexual couples.

In dissent, Chief Justice John Roberts frets that the majority's rationale could apply equally well to polygamous unions. He writes:

Although the majority randomly inserts the adjective "two" in various places, it offers no reason at all why the two-person element of the core definition of marriage may be preserved while the man-woman element may not. Indeed, from the standpoint of history and tradition, a leap from opposite-sex marriage to same-sex marriage is much greater than one from a two-person union to plural unions, which have deep roots in some cultures around the world... If not having the opportunity to marry "serves to disrespect and subordinate" gay and lesbian couples, why wouldn't the same "imposition of this disability" [] serve to disrespect and subordinate people who find fulfillment in polyamorous relationships?

In effect, Obergefell self-consciously enshrines the sea-change in American public opinion about homosexuality in new-found fundamental rights. It openly admits to having "new insights and societal understandings" of Equal Protection and applying them to gay marriage. To answer the Chief Justice's challenge, a similar sea-change in American views of polygamy has not happened. Yet.

The danger here is not that the current Court is prepared to recognize a "fundamental right" to polygamy. Rather, it is that Obergefell paves the way for a future Supreme Court to apply future "new insights and societal understandings" of Equal Protection to polygamy. Should polygamy become tolerated by the American public, subsequent Supreme Court opinions may enshrine changed public opinion in a new-found fundamental right to multiple marriage partners.

Of course, polygamy may never slide down Obergefell's slippery slope. Perhaps the Court's "new insights" will convince it that polygamy is irrevocably intertwined with the abuse of women and children and will, if anything, reinforce opposition to polygamy. The 1878 Reynolds v. United States decision allowing bigamy to be prosecuted criminally despite religious belief (of Mormons, in that case) relied partly on (rather thin) social science claims that "polygamy leads to the patriarchal principle." Hopefully, the science has improved since then. Given the intervening women's movement, there ought to be studies of the impact of polygamy on women that were unavailable in 1878.

On the other hand, here are three reasons to worry that polygamy may slide down the slippery slope sooner rather than later:

  1. Polygamy appears to be increasing in the US, or at least, more common than was thought. Roberts cites a 2009 Newsweek article that estimated there were more than 500,000 polygamous families in the United States. Some are Mormons. Some (NPR has cited estimates of 50,000-100,000) are Muslims. (The problem is not limited to the US. Last week, the Daily Mail reported that there are "as many as 20,000 polygamous Islamic unions in the UK.")
  2. The popularity of Sister Wives, a reality TV program about a "normal" polygamous family, suggests there has been some headway in presenting polygamy as an acceptable alternative lifestyle.
  3. In August of last year, a federal court struck down part of Utah's criminal prohibition against polygamy. It is now legal to live with multiple partners one considers spouses, although only one of them may be a legal spouse. The case was brought by the Browns of Sister Wives fame.

Here's to hoping the Supreme Court's future "new insights and societal understandings" of Equal Protection are better and not just newer than its old ones.