California Code, Penal Code - PEN § 30372

(a) If a person attempts to purchase or otherwise acquire ammunition and the sale or other transfer is not approved by the Department of Justice pursuant to Section 30370 because the person is prohibited from possessing ammunition pursuant to Section 30305, the department shall notify the local law enforcement agency with primary jurisdiction in which the person was last known to reside of the attempt.

(b) A local law enforcement agency that receives a notification pursuant to subdivision (a) may investigate whether the person is in unlawful possession of a firearm. However, the law enforcement agency shall not contact the person until it has attempted to confirm both of the following:

(c) Subdivision (a) does not apply if the sale or other transfer is not approved only because the address in the Automated Firearms System does not match the address on the person's identification, if there is a matching file with the same name, date of birth, and identification number.

(d) This section does not authorize a law enforcement agency to conduct a search without a warrant.