California is the only state in the union with a program to confiscate guns from people who bought them legally but were later disqualified, the Los Angeles Times reported Tuesday.
Attorney General Kamala Harris said California has more than 19,700 gun owners who are no longer qualified to possess firearms.
They are identified by analysts who track gun sales back to 1996 and match them against databases listing criminal convictions, restraining orders and mental health detentions.
For the past five years, California's gun apprehension teams have been sweeping through neighborhoods in unmarked trucks to retrieve guns from owners no longer permitted to have firearms.
To date more than 10,000 guns have been collected.
"This is about prevention," Harris said.
California's program is being studied as a potential model for the nation.