Good tenant with bad partner

[Rafael Norat]

I have a good, qualified tenant who has her husband wanting to move in. Her husband however has a criminal past and does not pass our screening process. She has recently moved in about 3 month ago. How would you address? My initial thoughts are to tell her he does not qualify and is not allowed to move in. But how can I really enforce in the long run? She can simply say ok and have him there quietly. Any thoughts here? 1 year lease. Thanks. Rafael