29. Why Obergefell Doesn’t Lead to Polygamy

—and why that matters for constitutional debate

Every time the law moves forward, someone asks: But where does it stop?

When the Supreme Court decided Obergefell v. Hodges in 2015, critics warned that the ruling would open the door to polygamy. If marriage is no longer limited to a man and a woman, they asked, why not to three people? Or five? Or an entire commune?

It’s the classic slippery slope argument. And on the surface, it might seem logical: once the state starts redefining marriage, where do the boundaries go?

But here’s the thing: Obergefell didn’t redefine marriage in every way. It expanded who could enter into the existing structure, not how that structure worked. And that difference matters—a lot.

Let’s walk through why Obergefell doesn’t logically (or legally) require the recognition of polygamy.

Kennedy’s Opinion Was About Who, Not How Many

Justice Kennedy was clear about the kind of marriage the Court was talking about: a two-person union grounded in emotional intimacy, legal commitment, and public recognition. He described marriage as a “union unlike any other in its importance to the committed individuals and to the society in which they live.”

Same-sex couples, Kennedy wrote, are “similarly situated” to opposite-sex couples in their capacity to enter that kind of union. The constitutional problem wasn’t the number of people—it was the exclusion of some people from the existing institution.

Polygamy, by contrast, doesn’t just ask who can marry. It challenges the numerical structure of marriage altogether. It introduces a qualitatively different model, one with multiple overlapping legal relationships, often involving asymmetrical power dynamics.

So while Obergefell said the right to marry includes same-sex couples, it didn’t say marriage has no boundaries. It said the boundaries must be drawn fairly.

Polygamy Raises a Different Set of State Interests

Laws banning same-sex marriage were often rooted in moral disapproval, as the Court noted in earlier cases like Romer v. Evans and Lawrence v. Texas. But that kind of moral disapproval is not, by itself, a legitimate basis for denying constitutional rights.

Polygamy, on the other hand, has historically been regulated for administrative, economic, and social reasons, not just moral ones. Courts and legislatures have cited concerns about:

• Coercion and abuse, especially of women and children in closed religious communities

• Legal complexity in areas like taxation, inheritance, and benefits

• Disruption of legal systems designed around dyadic (two-person) relationships—think spousal privilege, custody laws, or divorce proceedings

You may disagree with those justifications. But the point is this: they are grounded in governance, not just morality. And courts tend to give the state more leeway when laws address practical policy concerns.

So the constitutional analysis is different, not because polygamy is inherently less worthy, but because the state’s regulatory rationale is categorically distinct.

Doctrinal Openings, but Legal Distinctions: Harrison’s Take

In his article On Marriage and Polygamy, law professor Jack B. Harrison reframes the slippery slope concerns. He sees them not as scare tactics, but as legitimate doctrinal questions.

Harrison argues that the logic of Obergefell—rooted in dignity, autonomy, and equal protection—narrows the range of constitutionally acceptable justifications for excluding people from marriage. Appeals to tradition or abstract fears about social breakdown no longer suffice.

So does Obergefell legalize polygamy? No. But Harrison says it raises the bar for defending its exclusion. States must now articulate concrete harms, not just invoke custom or discomfort.

He also examines the historical roots of anti-polygamy law, particularly Reynolds v. United States (1879), where the Court upheld criminal bans on polygamy by describing it as “odious” and linking it to “Asiatic and African peoples.” That racialized moralism would not survive constitutional scrutiny today. Obergefell, by contrast, rejects lawmaking rooted in animus.

Harrison’s ultimate point: courts may still uphold anti-polygamy laws, but only if they’re based on actual, demonstrable harms, not inherited prejudice or outdated assumptions.

Tradition Still Matters—But It’s Not Everything

A core conservative legal argument is that tradition determines constitutional meaning: if a right wasn’t recognized historically, it probably doesn’t exist.

Obergefell complicated that. It acknowledged that marriage has evolved over time to include interracial couples, to allow no-fault divorce, to recognize women’s full legal autonomy. The fact that same-sex marriage lacked historical precedent didn’t disqualify it as a right.

Still, the Court didn’t abandon tradition entirely. It reaffirmed marriage’s centrality and continuity, arguing that same-sex couples sought entry into a meaningful institution, not its reinvention.

By contrast, polygamy stands outside that tradition. It remains unlawful in all 50 states, and Reynolds is still on the books. Kennedy’s “emerging consensus” in favor of same-sex marriage simply doesn’t exist when it comes to plural marriage.

So, Does the Slippery Slope Slide?

The fear that Obergefell launched a runaway train misunderstands the decision’s architecture. Kennedy didn’t blow open the doors of marriage but instead clarified who had a right to enter.

Obergefell creates doctrinal tensions, but not collapses. To challenge anti-polygamy laws, litigants would need a new case, with new facts, and compelling evidence that plural marriage can function within modern legal systems without undermining core state interests.

Until then, Obergefell stands not as a slippery slope, but as a constitutional floor. It affirms that marriage is meaningful, and that exclusion must be justified.

How should courts decide when a constitutional principle—like liberty or equality—extends to new contexts? What anchors that kind of expansion?