Lawyers for a family made famous by the TV show "Sister Wives" are set to ask a federal appeals court on Thursday to uphold a ruling that decriminalized polygamy in Utah.

The case is scheduled to come before the 10th Circuit Court of Appeals in Denver after the Utah Attorney General appealed the ruling that struck down key parts of the state law banning polygamy.

State attorneys say they don't plan to charge plaintiff Kody Brown and his four wives if the law stands, but it should stay on the books because it helps curb abuses like underage marriage.

The Brown family says their reality show "Sister Wives" shows polygamous unions can be as healthy as monogamous ones. They argue that making marriages like theirs a crime violates the right to privacy and freedom of religion.

The family won a legal victory in 2013, when U.S. District Judge Clark Waddoups found that a key part of Utah's bigamy law forbidding cohabitation violated the Brown's right to religious freedom and struck it down. Bigamy, or holding multiple marriage licenses, is still illegal.

The decision was hailed as a landmark case that removed the threat of arrest for plural families, but Utah said that it could weaken their ability to go after polygamists like jailed leader Warren Jeffs.