California Code, Unemployment Insurance Code - UIC § 454

(a) Services customarily performed in more than one state by an individual for a single employer shall be deemed to be services performed entirely within any one of the states (i) in which any part of the individual's service is performed, or (ii) in which the individual has his residence, or (iii) in which the employer maintains a place of business, if there is in effect as to such services an election by the employing unit with the acquiescence of the individual, approved by the agency charged with the administration of such state's unemployment compensation law pursuant to which all the services performed by such individual for such employer are deemed to be performed entirely within such state.

(b) Services on vessels engaged in interstate commerce wherever performed shall be deemed performed within this State or any other state on the basis of the location of the operating office of the employer from which the operations of the vessel are ordinarily and regularly supervised, managed, directed, and controlled.