It is in fact technically illegal, and you could be charged with a felony for concealment of the fixed blade. There is no specification on the length of the fixed blade that can or cannot be concealed as written in the California Penal Code, thus any fixed blade of any length is considered illegal if carried concealed. Now whether or not a police officer would choose to arrest you and submit for prosecution case where a person carries a 1 inch fixed blade is up to the discretion of the officer, and personally I find that concerning. I feel like any district attorney would find it ridiculous to push for prosecution of a felony charge on someone who carries such a small knife in their pocket, it is however something they could do if they should choose. Now consider for a second that a 1 mm fixed blade knife is manufactured, this to would also be considered a felony if concealed And that's why this law is ridiculous.