If and when he moves to a pet friendly place he will have him. There is a backup plan of who would look after Bandit should my son have to then move again and needs time to find the right place.
The house belongs to the landlord, not the renter. You agree to abide by the lease terms but people think it's ok to flout them.
People wonder why so many rental places say no pets.
That can be for many reasons including that people who have had pets before when told not to have ruined it for others and the landlord is fed up.
To me, a contract is a contract. If you don't like it move somewhere else.