Richard, looking at the CA handgun restrictions, it would seem legal. The Brace does not change the classification of the Pistol, the fore-grip is ATF approved for a handgun and the Barrel Shroud is excepted if it encloses the barrel and it does. I would just call a local FFL and ask as they would likely know CA gun laws best. Details under Handguns here : budsgunshop.com/feeds/state_reg/california_restrictions.pdf

I believe it would make the handgun Illegal under CA law "✘ Any semi-automatic pistols that do not have a fixed magazine, but have any one of the following: ○ Threaded barrel capable of accepting a flash suppressor, forward handgrip, or suppressor. ○ Second handgrip ○ A shroud that is attached to, or partially or completely encircles, the barrel that allows the bearer to fire the gun without burning their hand, ​except a slide that encloses the barrel. " But I would suggest asking your local FFL holder