This article is from the California Driving (and Surviving) FAQ, by "George J Wu" email@example.com with numerous contributions by others.
from firstname.lastname@example.org (Bill Karwin) on 18 Mar 1993:
I called 1-800-927-HELP and the answer is yes, the insurance company does
have a right to ask for the id's of the housemates if they are to be
occasional drivers. The only alternative is to exclude these housemates
from coverage, by providing their names (not their driver's license #).