Okay, AR and AK series rifles had to be purchased by August 8,2000 and then registered with the CA DOJ by January 23,2001. Originally, you only had until December 31,1999 to purchase these, but people were removing the pistol grips and selling them to get around the registration requirement. This was outlawed as of August 8, 2000. And ALL variants of AR and AK were required to be registered by January 23, 2001. The date for registration of AR and AK variants was adjusted from December 31, 2000 to January 23,2001. You are not prohibited from owning these weapons if they are registered, BUT you may not bring any more of these into the state AND you may not sell or give these weapons to anyone in the state, including spouse, children or blood relatives.
Other "assault weapons" such as the FAL are being sold, but without the pistol grip so as to comply with these laws.
This is really a very long and complicated topic. For further info contact the CA DOJ.
As of January 1,2001, NEW handguns offered for sale in the state of CA must pass, and be certified as having passed a "Drop Test". There are currently over 400 pistols and revolvers that have passed and are certified, and many that have passed but are not yet certified. Again, the DOJ has a list available on their website that is updated frequently.
http://caag.state.ca.us/firearms/certlist.htm