Alabama Attorney General Luther Strange is supporting the National Rifle Association as it opposes a federal law restricting handgun sales to people ages 18 to 20.
Strange's office has filed a brief in the U.S. Supreme Court in support of the NRA's challenge.
The brief was joined Friday by attorneys general in 21 other states.
Strange's brief challenges a 1968 federal law that prohibits licensed firearms dealers from selling to people under 21 even though those same people aren't forbidden from possessing or using handguns.
The law was upheld by the Fifth Circuit Court of Appeals, and that ruling is being appealed to the U.S. Supreme Court.
The brief argues that 18- to 20-year-olds should be allowed to exercise the right to bear arms.