"SOME times" tweeted Rick Santorum, not at all credibly, "I hate it when what I predict comes true." Mr Santorum, a once and doubtless future presidential candidate from the social-conservative wing of the Republican Party, was referring to the ruling by a federal judge that found part of Utah's law prohibiting polygamy unconstitutional. Mr Santorum and others of his ilk warned that legalising same-sex marriage would inevitably lead to legalising polygamy. And at first blush, it appears that those warnings have come true. In June the Supreme Court refused to uphold California's Proposition 8, which defined marriage as a union between a man and a woman, and it struck down the Defense of Marriage Act (DOMA), which barred the federal government from recognising same-sex marriages. And lo, in December, here comes a federal court saying have a wife or four. So is Mr Santorum correct—did legalising gay marriage lead to legalising polygamy? There are two answers to that question. The first, on the legal merits, is a clear no. The court's ruling cites neither Hollingsworth v Perry nor United States v Windsor, the two gay-marriage cases the Supreme Court decided in June. It does not mention gay or same-sex marriage anywhere. To the extent that a slippery slope exists at all, it was Lawrence v Texas, which struck down Texas's anti-sodomy law in 2003, not either of the more recent cases, that first shoved marriage down the hill. Before then, the ruling explains, "'[T]he good order and morals of society' served as an acceptable basis for a legislature, it was believed, to identify 'fundamental values' through a religious or other perceived ethical or moral consensus, enact criminal laws to force compliance with these values, and enforce those laws against a targeted group." Lawrence shattered that belief: what consenting adults do in the bedroom is their own business, provided it harms nobody else. Furthermore, the Utah ruling did not strike down a law against bigamy; it struck down a plank of Utah's anti-polygamy law that barred "religious cohabitation". States can still say one person, one marriage license; they just cannot keep married people from living with others in "personal relationship[s] that they knew would not be legally recognised as marriage."

The second answer is more subtle. Lawrence, as the Utah court noted, established "a fundamental liberty interest in sexual conduct." This does not mean that there now exists a positive constitutional right to whatever sexual conduct anyone would like. It means, instead, that if the government wants to regulate sexual conduct that regulation must meet rational-basis review—it must rationally further some legitimate government interest. Neither Texas's sodomy law, DOMA, nor Utah's law banning extra-marital cohabitation did, so they're gone. The decision striking down religious cohabitation did not follow from the decision striking down DOMA, but they have the same parentage, and that parent ruling says, in effect, stay out of consenting adults' bedrooms.

Now, I think it's clear that Mr Santorum and Tony Perkins and other religious conservatives dislike Lawrence: they may like government small in the marketplace, but they want it looming in the bedroom. And it's worth asking them that if in an ideal world they would like to see this Utah ruling and the DOMA ruling overturned, do they also want to strike down Lawrence? Should we reinstate anti-sodomy laws? If a religiously-conservative household happens to live next to a gay couple, should the former be able to call the cops and get the latter arrested for what they do in their bedroom. And what about Griswold v Connecticut, which struck down laws that made it illegal to counsel married couples about contraception? That too involved an expansion of the realm of sexual privacy: should we roll that back too?

Of course, it's also fair for them to ask the inverse question of gay-marriage supporters like me: do I accept that a hands-off approach to legislating sexual morality leads to polygamy (in practice, if not strictly legally) as well as same-sex marriage? Jonathan Tobin is right to point out that polygamy can inhibit freedom, though of course, bad heterosexual marriages can do that too; I'm not sure I buy the argument he cites that "[p]olygamy in all its forms is a recipe for social structures that inhibit and ultimately undermine social freedom and democracy." And he is right to say that people must accept the costs as well as the benefits of strict and lax legal views on sexual morality. But given the choice between, say, Saudi Arabia and Sweden—between the prospect of a world in which consenting adults can choose to enter into polyamorous marriages, and one in which cops can break down the doors of consenting adults suspecting of getting it on with same-sex partners—I know which one I'd choose.

(Photo credit: AFP)