Utah Code Title 77. Utah Code of Criminal Procedure § 77-7-12. Detaining persons suspected of shoplifting or library theft--Persons authorized

(1) A peace officer, merchant, or merchant's employee, servant, or agent who has reasonable grounds to believe that goods held or displayed for sale by the merchant have been taken by a person with intent to steal may, for the purpose of investigating the unlawful act and attempting to effect a recovery of the goods, detain the person in a reasonable manner for a reasonable length of time.

(2) A peace officer or employee of a library may detain a person for the purposes and under the limits of Subsection (1) if there are reasonable grounds to believe the person violated Title 76, Chapter 6, Part 8, Library Theft.