State v. Friesen
In State v. Friesen, 1999 UT App 262, 988 P.2d 7, a Utah police officer stopped a vehicle bearing only a rear Wyoming license plate.
The police officer initiated the stop based on the erroneous assumption that Wyoming law required both a front and a rear license plate. Id.
On appeal, the State argued that "reasonable, articulable suspicion" encompasses a police officer's understanding of what the law is. Responding specifically to that argument, the court of appeals held that "the facts about which an officer must have a reasonable, articulable suspicion at the time of a traffic stop are those regarding the conduct of the person stopped, not the nature of the law." Id.
The Friesen court ultimately concluded that if the police officer's suspicion is about what the law prohibits, "the officer has no basis upon which to make or defend the stop." Id.