The Child Passenger Protection Act requires that all children under age 8 be properly secured in an appropriate child safety restraint system. This includes the use of booster seats, which must only be used with a lap/shoulder safety belt. If the back seat of the vehicle is not equipped with lap/shoulder type safety belts, a child weighing more than 40 pounds may be transported in the back seat without a booster seat, secured with a lap belt only.
As of January, 1, 2019 the Child Passenger Protection Act is amended to include the requirement for children under age 2 years to be properly secured in a rear-facing child restraint system unless the child weighs 40 or more pounds or are 40 or more inches tall.
For more information visit: https://www.cyberdriveillinois.com/departments/drivers/childsafety.html