California Code, Government Code - GOV § 3574

(a) The employer reasonably doubts that the employee organization has majority support or reasonably doubts the appropriateness of the requested unit. In that case, the employer shall notify the board, which shall conduct a representation election or verify proof of majority support pursuant to Section 3577 unless subdivision (c) or (d) applies.

(b) Another employee organization either files with the employer a challenge to the appropriateness of the unit or submits a competing claim of representation within 15 workdays of the posting of notice of the written request. If the claim is evidenced by the support of at least 30 percent of the members of the proposed unit, a question of representation shall be deemed to exist and the board shall conduct a representation election pursuant to Section 3577. Proof of that support shall be submitted to either the board or to a mutually agreed upon third party.

(c) There is currently in effect a lawful written memorandum of understanding between the employer and another employee organization recognized or certified as the exclusive representative of any employees included in the unit described in the request for recognition, unless the request for recognition is filed not more than 120 days and not less than 90 days prior to the expiration date of the memorandum of understanding, provided that, if the memorandum of understanding has been in effect for three years or more, there shall be no restriction as to the time of filing the request. The existence of a memorandum of understanding, or current certification as the exclusive representative, shall be the proof of support necessary to trigger a representation election pursuant to Section 3577 to determine majority support when a request for recognition is made by another employee organization.

(d) Within the previous 12 months, either another employee organization has been lawfully recognized or certified as the exclusive representative of any employees included in the unit described in the request for recognition, or a majority of the votes cast in a representation election held pursuant to Section 3577 were cast for “no representation.”