Wednesday Warrior question

This episode was recently repeated on Cozi, so I'm sure someone will know what I'm talking about...anyhow, Malloy and Reed stop a car with a broken tail light. The kid driving the car was a little nervous, and Malloy didn't see anything wrong, but Reed noticed children's clothes in the back seat of the car and noted that they were the wrong size for the driver's young cousin (he mentioned that the clothes were for his cousin and mentioned the boy's size). The guy tried to run, but Reed stopped him and they arrested him.

My question is this...just what did the guy get arrested for? I'm no legal scholar, but having the wrong size baby clothes in your car is not a crime, and the broken light would have only gotten him a ticket. Was the car stolen? Were there drugs hidden under the clothing? It was not explained why the kid got arrested!