CA Pub Util Code Section 21412

Any certificate, permit, or license required by the United States for an aircraft shall be carried in the aircraft at all times while the aircraft is operating in the state, shall be conspicuously posted in the aircraft where it may be readily seen by passengers or inspectors, and shall be presented for inspection upon the demand of any peace officer, any other officer of the state or of a political subdivision, or member, official, or employee of the department, authorized by Section 21252 to enforce the aeronautics laws, or any official, manager, or person in charge of any airport upon which the aircraft lands, or upon the reasonable request of any person.