registration. Repeat Yessir until he leaves you with a warning or ticket.
Not driving?
Utah Code 77-7-15. A peace officer may stop any individual in a public place when the officer has a reasonable suspicion to believe the individual has committed or is in the act of committing or is attempting to commit a public offense and may demand the individual's name, address, date of birth, and an explanation of the individual's actions.
(If you want legal advice on how to apply this, talk to your lawyer)