"Discrimination on the basis of transgender status is discrimination on the basis of sex," the judge wrote in the case of a Georgia sheriff's deputy who sued.
The announcement comes as the result of a federal lawsuit that alleged officers unfairly targeted and arrested innocent queer men.
The trial has gone on for six weeks.
The law, set to go into effect July 1, "violates multiple provisions of the Utah Constitution," the suit says.
"We are living in a state of emergency."
James MacDougall fathered 15 children without telling the women using his services that he had fragile-X syndrome.
The bill would require school employees to potentially out students to their parents.