Except for New Hampshire, all states and the District of Columbia require adult front-seat occupants of motor vehicles to use seat belts. Adult rear-seat passengers are also covered by the laws in 31 states and the District of Columbia. Children are covered by separate laws.

State seat belt laws are divided into two categories: primary and secondary. Primary seat belt laws allow law enforcement officers to stop a motor vehicle and to issue a ticket or citation to a driver or passenger for not wearing a seat belt without any other traffic offense having occurred. Secondary seat belt laws only allow law enforcement officers to issue a ticket or citation for not wearing a seat belt when there has been another traffic offense by an occupant of the vehicle for which the occupant may be issued a ticket or citation.

In California, seat belt laws are categorized as primary, meaning that law enforcement officers have the authority to stop a vehicle and issue a citation to the driver or passengers solely for not wearing a seat belt. This applies to both front-seat and rear-seat occupants. California Vehicle Code section 27315 mandates that all occupants of a motor vehicle must wear a seat belt. This law covers adults and extends to children with specific child restraint requirements under California Vehicle Code section 27360, which requires that children be secured in an appropriate child passenger restraint system until they are at least 8 years old or 4 feet 9 inches tall. Failure to comply with these seat belt laws can result in fines and penalties. It's important to note that these laws are subject to change, and it is advisable to consult with an attorney or the latest state statutes for the most current information.