The court unanimously agreed with the findings of the state's Judicial Conduct Commission, which recommended the removal of Judge Walter Steed for violating the state's bigamy law.
Steed has served for 25 years on the Justice Court in the polygamist community of Hildale in southern Utah, where he ruled on misdemeanor crimes such as drunken driving and domestic violence cases.
The commission last year sought his removal from the bench after a 14-month investigation determined Steed was a polygamist and had violated Utah's bigamy law. Bigamy is a third-degree felony in Utah punishable by up to five years in prison and up to $5,000 in fines.
"When the law is violated or ignored by those charged by society with the fair and impartial enforcement of the law, the stability of our society is placed at undue risk," the court's ruling said.
Steed, who also works as a truck driver, scheduled a news conference for later Friday to discuss the ruling. He was paid a few hundred dollars monthly for serving in the part-time judicial position.
A receptionist at the Judicial Conduct Commission said neither the commission nor its attorney would comment on the case.
Friday's court decision did not address whether Steed should face criminal charges, saying only that the judge acknowledged his illegal behavior and "has given every indication that he intends to continue his 'plural marriage' arrangement."
Justice Court judges are appointed to four-year terms by city councils or county commissions. They are not required to have any legal training.
The initial complaint against Steed was filed in 2003 by Tapestry Against Polygamy, a group founded by women who had left the secretive colonies.
Steed legally married his first wife in 1965, according to court documents. The second and third wives were married — or "sealed" as the Fundamentalist Church of Jesus Christ of Latter Day Saints refers to it — to him in religious ceremonies in 1975 and 1985.
He has 32 children by the three women, who are sisters, court documents said.
Plural marriage was an original tenet of the mainline Mormon church, but the faith abandoned the practice in 1890. About 30,000 polygamists, who split from the main church into various fundamentalist sects, are believed to be living in Utah, the Southwest, Mexico and Canada.