Cal. CIV § 1812.216

(a) Any waiver by a purchaser of the provisions of this title shall be deemed contrary to public policy and shall be void and unenforceable. Any attempt by a seller to have a purchaser waive rights given by this title shall be a violation of this title. (b) In any proceeding involving this title, the burden of proving an exemption or an exception from a definition is upon the person claiming it.