Utah Code § 77-7-13: Arrest without warrant by peace officer -- Reasonable grounds, what constitutes -- Exemption from civil or criminal liability.

(1) A peace officer may arrest, without warrant, any person the officer has reasonable ground to believe has committed a theft under Title 76, Chapter 6, Part 8, Library Theft, or of goods held or displayed for sale.

(2) A charge of theft made to a peace officer under Title 76, Chapter 6, Part 8, Library Theft, by an employee of a library, or by a merchant, merchant's employee, servant, or agent constitutes a reasonable ground for arrest, and the peace officer is relieved from any civil or criminal liability.