Cal. Penal Code § 26368

Section 26350 does not apply to, or affect, the open carrying of an unloaded handgun by a member of an organization chartered by the Congress of the United States or a nonprofit mutual or public benefit corporation organized and recognized as a nonprofit tax-exempt organization by the Internal Revenue Service while on official parade duty or ceremonial occasions of that organization or while rehearsing or practicing for official parade duty or ceremonial occasions.