Hawaii law requires children under the age of four to ride in a child safety seat and children ages of four through seven to ride in a child safety seat or a booster seat when traveling in a motor vehicle. The driver will be held responsible for compliance with the law. Violators of the law are required to attend a 4-hour class and may be assessed a fine.
Find more detailed information at the Hawaii Department of Transportation. http://hidot.hawaii.gov/highways/safe-communites/child-passenger-safety/