Not right.
Most of the several so-called "assault weapons" laws in Kalifornia apply to center-fire rifles which can accept a detachable magazine. Such rifles may not have any of a list of evil features, such as a flash-suppressor, pistol-grip, adjustable stock, or some other features.
By installing a "bullet-button" in place of the standard magazine release button, one can then legally have ALL of the evil features.
There is nothing illegal about having a magazine release on a rifle which has none of the evil features. That is, unless the rifle otherwise qualifies as a so-called "assault weapon" under one of the other assault weapon laws.
I stand corrected although my answer was based on picturing a standard ar15/ak47 modern sports rifle. Fortunately, I live in a state whose state government’s interest is in expanding rather than reducing its citizens’ firearms freedoms.
A California friend had to choose a bullet button ar15. As I recall, the San Berdoo jihadis had illegally modified their weapons to replace the bulletin buttons making their crimes that much more heinous. (Everyone seems to forget that their main killing weapons were to be bombs (which failed) rather the guns). Just like the Santa Barbara killer killed half of his victims with a knife.
Don’t some of these new laws basically outlaw nearly all semi autos?