Cal. Pub. Util. Code § 7943

(a) It is the intent of the Legislature that when the commission has no reasonable alternative other than to create a new area code, that the commission do so in a way that creates the least inconvenience for customers.
(b) The commission shall request that the Federal Communications Commission grant authority for the commission to order telephone corporations to assign telephone numbers dedicated to mobile telephony service and mobile data service, as defined in Section 224.4, to a separate area code and to permit seven digit dialing within that technology-specific area code and the underlying preexisting area code or codes.
(c) Before approving any new area code, the commission shall first perform a telephone utilization study and implement all reasonable telephone number conservation measures.
(d) If the commission receives the grant of authority set forth in subdivision (b) and determines that further area code relief is needed, the commission shall exercise the authority granted to it in subdivision (b) unless it finds at least one of the following:
1. (1) Exercising the authority granted by subdivision (b) would be more disruptive to the customers where area code relief has been determined to be necessary.
2. (2) Exercising the authority granted by subdivision (b) will not adequately extend the life of the area code where relief has been determined to be necessary.
(e) The commission may not implement any authority granted by the Federal Communications Commission pursuant to subdivision (b), in a manner that impairs the ability of a customer to have number portability.