Most control of model rocketry is on the state and/or local level. 48 states adhere to a common code of regulation for model rocketry known as National Fire Protection Association (NFPA) Code 1122. This code defines the power, weight, and other limits to which a rocket must comply in order to be classified as a (relatively unregulated) "model rocket."The federal government is, in comparison, less involved in regulating model rocketry. Model rocket kits and motors must satisfy the same basic product safety requirements as those imposed by the Consumer Product Safety Commission on toys. For this reason, certain types of model rocket motors -- such as "G" and "reloadable" motors -- are available only to modelers age 18 or over.
Model rockets are exempt from FAA regulation (thanks to FAR 101.1), provided they are operated in a manner so as not to pose a hazard to aircraft. There is one exception to the general FAA exemption: you must notify the nearest FAA control tower of your activities when launching model rockets weighing between 454 and 1,500 grams, or whose total propellant mass is in the range between 113 and 125 grams.