Honestly your requirements are too stringent if you want a brand new rifle. The chances of you finding a new semi-auto for under $400 is very low. As others have said the SU-16 and Mini-14 would be good choices, but both will exceed your $400 price range if you want them new. You should also look at a PC9, PC40, or a M1 Carbine as well. Here is a list of most of the California legal semi-auto centerfire rifles. I might be missing a few, but you should look at these and see what tickles your fancy.
-Off-list AR-15 (configured with either a fixed magazine, or without a pistol grip and flash suppressor.)
-Off-list AK (configured with either a fixed magazine, or without a pistol grip and flash suppressor.)
-Mini-14/30
-SU-16 A,B,CA
-Beretta RX4 (Should be available to civilians in late 2007)
-Ruger PC9/40
-Ruger Deerfield
-Marlan Camp 9/45
-M1 Garand
-M1 Carbine
-M1A
-M1941 Johnson
-HK SL6
-HK SL7
-SKS
-Volquartsen Evolution
-Modified FAL
-Rasheed
-Hakim
-FN49
-VZ-52/57
-SVT
-MAS49
-Ljungman
-BAR
-Benelli R1
-Remington 7400
-1919
-Vickers
-M-31 Suomi
-PPSH-41(This one and the Suomi might not be long enough for California if you get the versions from Military Gun Supply)