ULC ministers officiate lawful marriage in all 50 states. Some years ago, Utah attempted to do an end-run around the US Constitution and passed a law which would have prevented ULC ministers from officiating marriage in that state. However, the church challenged the statute and won a permanent injunction in federal court, prohibiting the state from enforcing the law.
A copy of the court's decision can be found at:
Since the Utah legislature did not pass a subsequent law to remove the unconstitutional law from the books, it still exists, but cannot be enforced. This is not uncomomon in cases where a law is struck down by the courts, although Utah does make more of an effort to conceal this than other states do when a law is held to be illegal.
Some county clerks continue to tell people about the law, which I believe is a violation of the court's order, in that they are attempting to enforce the law illegally. If you encounter such a clerk, you may want to document the event, taking down his/her name and asking them specifically if that law has not been held to be unconstitutional and unenforceable. You may also wish to show them a copy of the above referenced court order. This will hopefully help to dissuade them from using their bully pulpit in the future to discriminate against ULC ministers, and put them on notice that they might be held personally liable for violating the court's order.
See also: weddings.ulc.net