As of July 1, 2008, California Penal Code Section 12072(f)(1) prohibits all Federal Firearms Licensees (FFLs), other than Type 03 or 06 FFLs, from shipping firearms to an FFL in California unless, prior to delivery, the FFL intending to deliver, sell or transfer the firearms obtains a verification approval number from the California Department of Justice (CADOJ) Bureau of Firearms. This includes transfers that occur at gun shows.

The verification approval number, which the Bureau of Firearms provides in a Firearms Shipment Approval letter, confirms that the intended recipient of the firearm shipment is properly licensed and listed in the state's database of persons/entities authorized to receive firearm shipments. If the intended CA FFL recipient is not listed in the state's database, the transaction will result in a Do Not Ship letter, and it is a crime for the intended recipient to receive the firearms (Penal Code Section 12083(c)(1)).

As a courtesy to impacted FFLs, the Bureau of Firearms has established an Internet application that is available to FFLs nationwide 24 hours a day 7 days a week (24/7) to obtain Firearms Shipment Approval letters. All Internet transactions will be handled on a secure server, and the information provided will be used solely for the purposes associated with the administration of the CFLC program. For FFLs that do not have Internet access, the Bureau has established a telephone service that allows nationwide FFL shippers to enroll and obtain Firearms Shipment Approval letters via telephone or facsimile prior to shipping firearms to a California FFL. However, the telephone service availability will be limited to Monday through Friday 8:00 a.m. to 5:00 p.m. Pacific Standard Time.

http://ag.ca.gov/firearms/cflcoverview.php