I have a friend who is a local forestry official, and he is a fellow knife guy. He told me that there is a federal limit to the length of a fixed blade on federal land. IIRC, it was an 8" limit. He brought it up to me when I was showing him my FBM.
I fail to believe that is a strictly enforced code (or even a valid one). Many here would have had experiences to let us know about the limit if there was one.
As for CA, I cant comment on its state laws, I am happy here in OR!