Can an insurer and a named insured agree that coverage under a motor vehicle policy will not apply while the vehicle is being used by a natural person or person designated by name?

'(e) Notwithstanding the foregoing subdivisions, the insurer and any named insured may, by the terms of such policy or by a separate writing, agree that coverage under the policy shall not apply while said motor vehicles are being used by a natural person or persons designated by name. Such agreement by any named insured shall be binding upon every insured to whom such policy applies.'

Uber v. Ohio Casualty Ins. Co., 247 Cal.App.2d 611, 616--617, 55 Cal.Rptr. 720, 724, reads: