My question involves vehicle registration or title in the state of: Iowa
i was turning onto a country road from a paved hiway on monday evening around 6 pm and a sheriffs deputy was at the stop sign of the country road coming off the road onto the paved hiway. i signaled and proceeded to turn left on to the country road and passed the sherrifs deputy who was stopped at the stop sign. i proceeded to drive down the road and about a mile down it i noticed that the sherrifs deputy was behind me. he stopped me and said my registration was expired. it was my sisters car and it turns out it was expired. he was sitting at a stop sign facing north and i was turng south onto the road. i dont see how he could have noticed that my registration was expired in his mirror especially when dust was flying from my car. he followed me for 2 miles before stopping me. is this an illegal stop. any help please.