Well, that's not exactly what happened. A federal court in Utah held part of Utah's anti-bigamy statute was unconstitutional in Brown v. Buhman (as in Kody Brown for all you Sister Wives fans out there). However, it's important to understand which part was at issue. The statute provided that:
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.Utah Code Ann. § 76-7-101(1) (2013).
Here, the Court lopped off that last bit ("or cohabits with another person") as a violation of the Browns' First Amendment Rights under the Free Exercise Clause, without a rational basis under the Fourteenth Amendment's Due Process clause. So, don't expect polygamous marriage licenses any time soon. The case presents an interesting development in the law, but I wouldn't go rewriting employee handbooks to address polygamy based on this decision.