The CFLC system
California Firearms Licensee Check System (CFLC)
The CA-DOJ web page is quite thorough.
"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.
(f) (1) (A) Commencing July 1, 2008, a person who is licensed pursuant to Chapter 44 (commencing with Section 921) of Title 18 of the United States Code may not deliver, sell, or transfer a firearm to a person in California who is licensed pursuant to Chapter 44 (commencing with Section 921) of Title 18 of the United States Code unless, prior to delivery, the person intending to deliver, sell, or transfer the firearm obtains a verification number via the Internet for the intended delivery, sale, or transfer, from the department. ... ... a violation of this section is a misdemeanor.
A Highlight from the FAQ
5. I am an FFL located outside of California. I ship/transfer firearms to California FFLs. Am I affected by the California Firearms Licensee Check (CFLC) Program?
Yes. You must obtain a Firearms Shipment Approval number from CADOJ Bureau of Firearms prior to delivering a firearm to a California FFL. Consequently, you will need to enroll in the CFLC program to obtain Firearms Shipment Approval numbers prior to shipping firearms to California.
Shippers who are not FFLs are not affected.
However, it is a business decision by any FFL to receive or decline to receive a shipment from a non-FFL shipper.