Cal. Const. art. IV, § 17

The Legislature has no power to grant, or to authorize a city, county, or other public body to grant, extra compensation or extra allowance to a public officer, public employee, or contractor after service has been rendered or a contract has been entered into and performed in whole or in part, or to authorize the payment of a claim against the State or a city, county, or other public body under an agreement made without authority of law.