If a rental unit has no certificate of occupancy how does this affect an unlawful detainer?

Apparently a landlord cannot collect rent in California, including past due rent in an unlawful detainer, if a rental unit has no certificate of occupancy (is “illegal”). If a landlord tries to evict a tenant from a unit with no certificate of occupancy does this mean a tenant invariably must move out? Should a tenant therefore avoid this defense in cases other than avoiding paying past due rent and who don’t care moving out? Are there situations where having no certificate of occupancy actually prevents or delays a landlord from evicting a tenant? If a landlord loses on other grounds does the tenant stay by default? For example, if a unit has no certificate of occupancy, a landlord does not request past due rent, but was shown to have retaliated and lost, could on those grounds a tenant stay, and in that case would a landlord be able to continue collecting rent?