Here is something at went on in Illinois not too long ago but involving "revoked FOID's". I think this is similar to what California is doing.
(From a government website, should be no copyright issues)
Press Release Date: December 7, 2011
http://www.isp.state.il.us/media/pressdetails.cfm?ID=608
Multi-Agency Collaboration Effort Credited
Rockford, Ill. -- The Illinois State Police, Rockford Police Department, Winnebago County Sheriff’s Office, Loves Park Police Department and the Bureau of Alcohol, Tobacco, and Firearms (ATF)
conducted a revoked Firearms Owner Identification (FOID) card operation this morning as part of the continuing “Operation Clean Sweep.”
The operation started early Wednesday morning with approximately 25-30 officers from Illinois State Police, Rockford Police, Winnebago County Sheriff’s, Loves Police and the ATF. Approximately 25 residences were targeted as part of the operation. T
he purpose of the operation was to ensure individuals with revoked FOID privileges were not illegally possessing or transferring firearms.
The results of Operation Clean Sweep include:
11 FOID cards seized
4 firearms recovered
67 cannabis plants seized from an in-door grow operation
400 grams of processed cannabis seized
2 arrests for outstanding warrants
1 arrest for failure to keep firearm transfer records
1 arrest for possession of cannabis with intent to deliver and manufacture of cannabis sativa plants