there is not federal law about leaving children unattended in car. however, eleven states have strict laws about leaving young children alone, either in car, in public places, or at home. in those states, it is against the law to leave anyone in a car who cannot get out without help. sometime, when a child is sleeping in the car and the parent doesn't want to wake the child up, the parent might decide to leave the child in the car and go into the store to get something. the parent can get arrested for this.