Circuit Judge Consuelo Callahan, another Bush appointee, dissented, saying the state had not shown a likelihood of success on appeal.
Plaintiffs challenging the law in court included Kim Rhode, who has won three Olympic gold medals in shooting events, and the California Rifle & Pistol Association.
California voters had in 2016 approved a ballot measure requiring gun owners to undergo initial background checks to buy ammunition, and pay $50 for a four-year ammunition permit.
Legislators amended the measure to require background checks for each ammunition purchase, starting in 2019.
Benitez in his decision rejected California's reliance on dozens of laws dating back to 1789 as "historical analogues" for ammunition checks and said the law had "no historical pedigree."
Persons:
Richard Clifton, Nate Raymond, Roger Benitez, Benitez, George W, Bush, Holly Thomas, Joe Biden, Consuelo Callahan, Rob Bonta, Kim Rhode, Chuck Michel, Benitez's Jan, Miral Fahmy
Organizations:
Reuters, Circuit, U.S, District, Democratic, Republican, Democrat, Plaintiffs, California, New York
Locations:
California, San Diego, New, Boston