Labor Code § 1018
CHAPTER 3. Class of Labor Employed; Labor Union Insignia
Any person who willfully wears the button of any labor union of this state, unless entitled to wear the button under the rules of such union, is guilty of a misdemeanor, and is punishable by imprisonment in the county jail for not more than 20 days or by a fine of not more than forty dollars ($40), or by both fine and imprisonment.