Not in California but generally 3d printing or otherwise self-manufacturing firearms is legal per the 2nd amendment, and publishing files is protected expressive activity (I bet there are some ITAR cutouts for weapons but I suspect that doesn't come into play here).
replySelf-manufacturing is definitely federally legal by statute but I don't think it is entirely clear that a constitutional right to self-manufacturing is incorporated to states or localities. Heller never mentioned manufacturing.
replyAnd on top of that, there is no protected right to 3d printers.
Regardless, it is 1000% more clear that states can't ban you from sending around gun design files.