CA extorts an annual fee from all gun manufacters who wish to sell thier product in CA. The scam is that it is done for "safety" purposes. The law however came into effect to prevent the selling of cheap guns which were easily available to low income individuals and therefore widely used by criminals because they were the guns they would come across most to steal (as many of thier victims live with them in low income areas.)
So to prevent the selling of these cheaper guns CA set requirements that such firearms at bargain prices will not meet, even those that were quite safe to the user.
The result though is that manufactuers only list thier most commonly sold models or those that there is a big market for. To pay a yearly annual fee and go through the procedures for a gun unlikely to sell much especialy if they have another model available for the consumer is not done.
This "approved firearms list" also has the requirements change every time some new lawmaker thinks extra restrictions can "reduce crime" or at least reduce gun purchases or ownership and others are gullable enough to buy it.
The only way to avoid additional new requirements is to already have the gun on the approved list and continue to pay a yearly extortion fee to keep it on the list. Otherwise it falls off the list and then must meet these new requirements, some of which would require a redesign of the pistol to meet.
Some of the new requirements in addition to the original ones include a magazine disconnect so the firearm cannot fire a round in the chamber without the magazine inserted, a chamber indicator to externaly show when it is loaded, and starting in 2010, microstamped capability to imprint miniature numbers on every cartridge fired.
So if the firearm you are interested does not come with the mag disconnect feature (which it is better without since that can be one more thing to go wrong, and who wants to not be able to defend themselves with one in the pipe while changing magazines or having the mag get disconected in a scuffle) or a loaded chamber indicator (so idiots can treat guns like they are not loaded because the idiot button says it is safe) then that firearm can no longer be put on the approved list even if the manufacturers are willing to pay the extortion fee.