Following on the rejection of interracial marriage bans in the 20th Century, the Supreme Court decision clearly shows that marriage should be a broadly applicable right—one that forces the government to recognize, as Friday’s decision said, a private couple’s “love, fidelity, devotion, sacrifice and family.”

The question presents itself: Where does the next advance come? The answer is going to make nearly everyone uncomfortable: Now that we’ve defined that love and devotion and family isn’t driven by gender alone, why should it be limited to just two individuals? The most natural advance next for marriage lies in legalized polygamy—yet many of the same people who pressed for marriage equality for gay couples oppose it.

This is not an abstract issue. In Chief Justice John Roberts’ dissenting opinion, he remarks, “It is striking how much of the majority’s reasoning would apply with equal force to the claim of a fundamental right to plural marriage.” As is often the case with critics of polygamy, he neglects to mention why this is a fate to be feared. Polygamy today stands as a taboo just as strong as same-sex marriage was several decades ago—it’s effectively only discussed as outdated jokes about Utah and Mormons, who banned the practice over 120 years ago.

Yet the moral reasoning behind society’s rejection of polygamy remains just as uncomfortable and legally weak as same-sex marriage opposition was until recently.

That’s one reason why progressives who reject the case for legal polygamy often don’t really appear to have their hearts in it. They seem uncomfortable voicing their objections, clearly unused to being in the position of rejecting the appeals of those who would codify non-traditional relationships in law. They are, without exception, accepting of the right of consenting adults to engage in whatever sexual and romantic relationships they choose, but oppose the formal, legal recognition of those relationships. They’re trapped, I suspect, in prior opposition that they voiced from a standpoint of political pragmatism in order to advance the cause of gay marriage.

In doing so, they do real harm to real people.

Marriage is not just a formal codification of informal relationships. It’s also a defensive system designed to protect the interests of people whose material, economic and emotional security depends on the marriage in question. If my liberal friends recognize the legitimacy of free people who choose to form romantic partnerships with multiple partners, how can they deny them the right to the legal protections marriage affords?

Polyamory is a fact. People are living in group relationships today. The question is not whether they will continue on in those relationships. The question is whether we will grant to them the same basic recognition we grant to other adults: that love makes marriage, and that the right to marry is exactly that, a right.

Why the opposition, from those who have no interest in preserving “traditional marriage” or forbidding polyamorous relationships? I think the answer has to do with political momentum, with a kind of ad hoc-rejection of polygamy as necessary political concession. And in time, I think it will change.

The marriage equality movement has been both the best and worst thing that could happen for legally sanctioned polygamy. The best, because that movement has required a sustained and effective assault on “traditional marriage” arguments that reflected no particular point of view other than that marriage should stay the same because it’s always been the same. In particular, the notion that procreation and child-rearing are the natural justification for marriage has been dealt a terminal injury. We don’t, after all, ban marriage for those who can’t conceive, or annul marriages that don’t result in children, or make couples pinkie swear that they’ll have kids not too long after they get married. We have insisted instead that the institution exists to enshrine in law a special kind of long-term commitment, and to extend certain essential logistical and legal benefits to those who make that commitment. And rightly so.

Source: It's Time to Legalize Polygamy