Cal. Water Code § 55336

Subject to Section 56133 of the Government Code, a district may sell water to any person, firm, public or private corporation, public agency, or other consumer outside the district when the governing body finds that the district has a surplus of water above that which is required by the consumers within the district. Additionally, a district may sell water to any person, firm, public or private corporation, public agency, or other consumer outside the district when the governing body finds that the sale of the water is required in response to an emergency as defined in Section 1102 of the Public Contract Code.