CA DOJ BOF = bullet button magazine lock is legal.
The Calguns Foundation had been working on a case (Haynie v Pleasanton) for a year, which had been kept low-profile, and was recently decided upon. The case was about an arrest over an "assault weapon" (the plantiff was arrested with a bullet button configured AR15 type rifle).
End result, charges were dropped and the rifle was returned to the owner.
Another result of that case, the CA DOJ BOF finally admitted, in Federal court, that the bullet button magazine lock is a legal device and when properly installed & used with a 10 round or less magazine can create a CA legal semi-auto centerfire AR15 type rifle.
“If someone has a gun and is trying to kill you, it would be reasonable to shoot back with your own gun.” - Dalai Lama (Seattle Times, 05-15-2001).