From what I understand, the no-pet clause is something in your lease, not a law created by the city or state. Which means that the landlord can change things if he/she so desires. The rules are going to be whatever the landlord decides.

I'd say that if you want the entire building to remain pet-free, you need to complain long and loud to the super and the landlord and anyone else you can find who has any influence in the matter.

If you were allergic to dogs and could prove that was why you rented in a no pet building, that would help your case. If you just don't like dogs, or this dog in particular, well, it seems that if the landlord okays the dog, you have to choice to either accept it or move. Sorry that that's the case.

The one thing I could find says that if the landlord does not do anything to remove the pet from the building for three months, the pet is allowed to stay. So there's a limited window of opportunity for the landlord to act.

In fact, there seem to be laws protecting pets in apartments, but none to prevent them from being there.

I have not googled NYC landlord tenant laws (believe they have some separate laws from NY state).

But I have a no-pets policy and that means no pets, period. Not even visitors or pet-sitting for someone. (Had a tenant pet sit once, and it caused problems, older dog, strange environment = accidents.) I feel bad as a pet owner, but at a LL, there are problems on so many levels it's just not worth it anymore. Allergic reaction/asthma in subsequent occupant (that's happened, had to yank & replace flooring), pet damage (that's happened), liability if a dog bites (that has not happened but I would so not want to get dragged into something like that).

Have you contacted the LL in writing? I'm not familiar with how much power supers have over buildings, but unless he's been given authority or power of attorney, this is a situation the LL might appreciate being made aware of and want to have final say so on the matter. There's a reason it's a No Pets building.

Just posting to confirm the above - this doesn't fall within the jurisdiction of NYC. Did you express your discomfort with the neighbor (first) and the super (second)? If you have spoken to both parties and they aren't respecting your request, then I'd follow moonshadow's advice and escalate it to the LL. I'd speak to the LL first and then, if that doesn't work, I'd write a letter to the LL and send it registered. As long as your lease says no-pets in the building and doesn't qualify that statement (i.e. that the LL or super can make exceptions on a case-by-case basis), your neighbor's arrangement is a violation of the lease so the LL will have to get rid of the dog.

The NYC Pet Laws affect or restrict *landlords*--they mean that if a landlord allows someone to have a pet in violation of the lease, then the landlord can't enforce that lease.

In your situation, the landlord's "no pets" clause is endangered, especially because his agent (the super) is very aware of the pet.

So I'd say, contact your landlord directly and say, "Did you know this guy is bringing his friend's pet in? And letting him stay overnight? And the super is allowing it? And did you realize that if you don't do anything about it, that this means every other tenant in the building is going to be able, legally, to have a pet, and you won't be able to do anything about it?
"I wanted to warn you, because I thought you might not want to lose the right to enforce your no-pet clause."