Laws that prohibit use of handheld phones or cellular devices in cars can restrict all use of--i.e. calls, texting, taking photographs, etc.--and can apply to use when the car is parked as well as in motion (just like laws against drinking alcohol in cars apply to drinking in parked cars or as a passenger only, and not just to when driving). While this officer was arguably taking an overly strict approach, in many states, the laws against using phones in cars would technically have supported him ticketing you.