As of January 1, 2012 the new California law for freedom from booster seats is 8 years or 4 feet 9 inches tall (57 inches). This increases the requirements for booster seats from 6 or 60 pounds. California joins 30 other states in the nation that all ready have this tough new law in effect. The law is based on a federal recommendation that children under 8 do not fit into adult belts well and that they do not fare well in car crashes when in adult belts. Of the old law (6 or 60 pounds), weight has nothing to do with a lap and shoulder belt fitting well. The fit has more to do with height. Here is a state by state list of booster seat laws and the fines instilled for first offense. See this map for booster seat laws state by state.