The tenants can call the city and complain (city may then do an inspection). If the city finds that the unit is not legal, they may order that the unit be vacated. In this situation there isn’t a notice of termination that can be given based on the fact that the unit is illegal so it is usually recommended that the landlord offer the tenant some kind of compensation to move out and if the tenant agrees a Form N11 can be signed by both parties to end the tenancy. When the unit is vacant the landlord can obtain the proper permits to ensure it is legal before renting again in the future.