California Code, Civil Code - CIV § 2988

(a) The Legislature finds that it is necessary to provide some protection for consumers who enter into lease contracts in which the lessee will bear the risk of the motor vehicle's depreciation.  This section is intended to provide relief to the consumer when an ostensibly inexpensive lease contract establishes an excessively low level of periodic payment which results, conversely, in an excessively high liability being imposed on the lessee at the expiration of the lease term because the lessor has failed to act in good faith in either estimating a residual value of the motor vehicle or establishing a level of periodic payment which bears no reasonable relation to the motor vehicle's reasonably expected depreciation during the lease term.  Therefore, the lessor will have the obligation to act in good faith and to come forward with competent evidence showing that the estimated residual value was so determined given the circumstances existing at the inception of the lease contract.

(b) Where the lessee is to bear the risk of the motor vehicle's depreciation and the lessee's liability on expiration of a consumer lease is based on the estimated residual value of the motor vehicle such estimated residual value shall be a reasonable approximation of the anticipated actual fair market value of the motor vehicle on lease expiration.  There shall be a rebuttable presumption that the estimated residual value is unreasonable to the extent that the estimated residual value exceeds the actual residual value by more than three times the average payment allocable to a monthly period under the lease.  The presumption stated in the preceding sentence shall not apply to the extent the excess of estimated over actual residual value is due to physical damage to the motor vehicle beyond reasonable wear and use, or to excessive use, and the lease may set standards for such wear and use if such standards are not unreasonable.

(c) For the purposes of this chapter, “fair market value” means the value the motor vehicle would have when sold in a commercially reasonable manner in the customary market for such motor vehicle.