This is a long time problem with Sportsman Guide. Absolutely nothing new and Posted about many many times here...
They refuse to ship the dumbest things that are in no way restricted or illegal in the state of California. I've seriously seen no ship to CA on AR dust covers and Glock slide cover plates.
Look at their magazine, 99% of it will not ship to CA. Their website was never any better. I gave up on them a long time ago and have not looked back.
Better prices and more California friendly service can be found elsewhere. Like SGAmmo for example. Or better yet, your local gun shops.