The state of Arizona requires that all children who are younger than eight years old and under 4'9" are properly secured in a child safety seat. For children under a year old, Arizona law requires a rearfacing car seat that supports the entire body, including the head and neck areas.Arizona car seat laws mandate that all children under 8 years old and shorter than 4'9″ have to use an appropriate child restraint system. Arizona law only requires booster seats in vehicles designed for ten or fewer people. The other exceptions to the child restraint rules include:. Arizona law requires all children under the age of five to be properly restrained in a child restraint system. Parents in Arizona are exempt from penalties for noncompliance with car seat laws under certain circumstances. Arizona Laws for Child Safety Seats. All children under five years old must ride in child safety seats while in motor vehicles. Arizona car seat requirements are designed to reduce the risk of injury and fatalities in the event of a car accident.