They can't change the terms of your written legal lease in the middle of a lease term. What does your written legal lease say, specifically, about pets, and when does the current lease term expire? If it permits you to keep a dog without limitation on size or breed, they cannot alter that until the end of the lease term. When your lease expires, however, they can renegotiate the terms of the lease, and if you don't like the new terms, you'd have to find a new residence. Many residential leases are 6 months to 1 year, then may have provisions that allow it to continue on a month to month basis thereafter until either party has a need to change terms. My guess is that your original lease agreement has expired or will in the coming months, leaving you vulnerable to a change in terms if you want to stay, which can include restrictions on a pet's breed and size. And it doesn't matter whether they force your neighbors to comply with the new policy or not; your lease is a separate legal agreement from theirs. I would start looking for a new place to live with your dog. I am guessing that you have something like a pit bull, Rottweiler, German Shepherd, or other breed on most insurance companies' breed restriction lists? If so, good luck finding any rental that will allow your dog. Since most insurance companies don't allow them, most landlords don't, either, for liability reasons. Those sorts of breeds are really only suitable for homeowners who have located appropriate insurance coverage thay doesn't exclude such dogs.