The case is Brown v. Buhman (D. Utah Dec. 13, 2013); the plaintiffs are the polygamists from the “Sister Wives” reality TV show. The court did not hold that the state must recognize polygamous marriages as legally valid; it held only that the Utah law criminalizing entering into even non-legally-recognized polygamous marriages was unconstitutional. (Special bonus: If the Tenth Circuit affirms the decision, this will create a split with State v. Holm (Utah 2006), which upheld the ban, and the U.S. Supreme Court is especially likely to agree to hear cases in which a state supreme court and the relevant federal circuit split on the constitutionality of a state law.)
More specifically: Utah law provides,
A person is guilty of bigamy when, knowing he has a husband or wife or knowing the other person has a husband or wife, the person purports to marry another person or cohabits with another person.
The court held that the “cohabits with another person” provision was unconstitutional, and the “purports to marry another person” clause could be saved from unconstitutionality by limiting to acts that purport to create a legal marriage (e.g., applying for a marriage certificate). The opinion is very long, and I’m on a family weekend trip, so I thought I’d just note the case for now; I hope to blog about it Monday.
Thanks to How Appealing for the pointer.