Emotional support animals and roommates

The roommate exemption

The Fair Housing Act does not reach a person choosing who to share their own living space with. If you are looking for a room in someone's home, or advertising for a housemate, that selection is outside the Act. So a prospective roommate can decline to live with your animal, and no accommodation duty attaches to them.

An existing roommate is different

Where you both already hold a tenancy from a landlord, the landlord owes you the accommodation duty and the roommate does not get a veto over it. What the roommate has is a practical position rather than a legal one, and in a shared tenancy a practical position is not nothing.

Allergies

Where the roommate has an allergy that is itself a disability, a landlord faces two accommodation duties and is expected to make a genuine attempt at both: air filtration, room reassignment, or in student housing a move. What a landlord cannot do is treat whoever complained first as automatically correct.

Joint tenancies and the practical problem

On a joint tenancy you are both liable for the whole rent and for damage, which means a roommate objecting to your animal is objecting to a risk they genuinely carry. That is not a legal veto and it is a real interest. Agreeing in writing that damage caused by your animal is yours removes most of the heat from the conversation and costs you nothing you were not already liable for.

If they move out

Your accommodation is with the landlord and does not lapse because the person who objected has gone. A landlord who granted it cannot revisit it on the arrival of a new roommate, although a new roommate with an allergy that is itself a disability puts the landlord back into the competing accommodation position.