According to TV4 proprietary lease §16 (could be a different number on your individual lease):

“The Cooperator unconditionally acknowledges, accepts and agrees that the carrying charges provided for herein are predicted on the following:

(b)That no dogs or other animals shall be harbored or kept on the demised premises…”

Two types of laws give an individual Shareholder the right to keep a pet, even if there is a "no pet" provision in the proprietary lease.

The first, and most widely known types of laws are municipal or local "Pet Laws" which deem that any such "no pet" provision is waived for the duration of the tenancy if the landlord fails to enforce the provision by commencing an action or proceeding within three months of the tenant's open and notorious harboring of the pet. http://codes.lp.findlaw.com/nycode/ADC/27/2/2/1/27-2009.1

The second category of laws which would enable a tenant to keep a pet in spite of a "no pet" rule are the federal state, and local laws which prohibit discrimination against the disabled. Such laws mandate that a housing provider grant a "reasonable accommodation" necessary for a disabled person to "use and enjoy" his or her home.

Recent developments in each type of law have enabled many individuals to keep pets. As you’ve probably noticed, there are many TV4 Shareholders and even Board Members having dogs and openly walking with them around the complex. As a result, other Shareholders want to execute their rights, and buy dogs too. While Co-op Boards may be within their rights to enact and enforce a "no pet" clause, such prohibitions fail in the face of superseding laws which give tenants the right to keep pets in their homes under certain circumstances.

Access Rights of Individuals with Disabilities and their Service Animals

The rights of persons with disabilities to use service animals are protected under a network of federal, state and local laws and regulations. Federal regulations under the Americans with Disabilities Act (“ADA”) specifies that:

“Service animals are defined as dogs that are individually trained to do work or perform tasks for people with disabilities. Examples of such work or tasks include guiding people who are blind, alerting people who are deaf, pulling a wheelchair, alerting and protecting a person who is having a seizure, reminding a person with mental illness to take prescribed medications, calming a person with Post Traumatic Stress Disorder (PTSD) during an anxiety attack, or performing other duties. Service animals are working animals, not pets. The work or task a dog has been trained to provide must be directly related to the person’s disability. Dogs whose sole function is to provide comfort or emotional support do not qualify as service animals under the ADA.

This definition does not affect or limit the broader definition of “assistance animal” under the Fair Housing Act or the broader definition of “service animal” under the Air Carrier Access Act.”

http://www.ada.gov/service_animals_2010.htm

The New York State Executive Law Article 15 HUMAN RIGHTS LAW specifically protects individuals who use guide dogs, hearing dogs and service dogs. According to § 292 Definitions:

31. The term "guide dog" means any dog that is trained to aid a person who is blind by a
recognized guide dog training center or professional guide dog trainer, and is actually used for such purpose.

32.The term "hearing dog" means any dog that is trained to aid a person with a hearing impairment by a recognized hearing dog training center or professional hearing dog trainer, and is actually used for such purpose.

33.The term "service dog" means any dog that is trained to work or perform specific tasks for the benefit of a person with a disability by a recognized service dog training center or professional service dog trainer, and is actually used for such purpose.”

Discrimination against persons with disabilities is prohibited under other New York laws,§296. Unlawful discriminatory practices(14):

"It shall be an unlawful discriminatory practice for any person engaged in any activity covered by this section to discriminate against a blind person, a hearing impaired person or a person with a disability on the basis of his or her use of a guide dog, hearing dog or service dog.”

These laws provide that service animals must be permitted in all areas of a facility where customers are generally permitted.

Companion Animals and Housing Issues

But just as a proprietary lease doesn’t allow a Housing Company to withhold essential services such as heat and hot water, or to unlawfully discriminate; a no-pet clause also is not always enforceable. For example, in New York City laws commonly referred to as the “Pet Law”, prohibit the enforcement of a “no pet” clause, even if there is an applicable “no pet” clause in the lease, if a landlord fails, within three months of his knowledge of a tenant’s harboring of a pet, to enforce the “no pet” provision. The law applies to both owners and renters, in apartment complexes, co-ops and condos, whether privately owned or government subsidized. Just as a landlord must accommodate a disabled tenant who requires a wheelchair, a companion animal must similarly be permitted. The only limitations are generally that the disability substantially interfere with a major life activity (work, social activities, etc.), and that the pet is under control (i.e. it would be reasonable to allow the pet). These disability laws are set forth in the Federal Fair Housing Act, as well as, the “ADA”, and in state and local human rights laws. Some federal laws allow pets for all people over 62 years of age in federal or federally-funded housing. Other laws allow animals trained as “service animals” to reside with their companion human.

New York New York City Administrative Code (new) - Article 1 - § 27-2009.1 Rights and Responsibilities of Owners and Tenants in Relation to Pets:

§27-2009.1 Rights and responsibilities of owners and tenants in relation to pets.

a. Legislative declaration. The council hereby finds that the enforcement of covenants contained in multiple dwelling leases which prohibit the harboring of household pets has led to widespread abuses by building owners or their agents, who knowing that a tenant has a pet for an extended period of time, seek to evict the tenant and/or his or her pet often for reasons unrelated to the creation a nuisance. Because household pets are kept for reasons of safety and companionship and under the existence of a continuing housing emergency it is necessary to protect pet owners from retaliatory eviction and to safeguard the health, safety and welfare of tenants who harbor pets under the circumstances provided herein, it is hereby found that the enactment of the provisions of this section is necessary to prevent potential hardship and dislocation of tenants within this city.

b. Where a tenant in a multiple dwelling openly and notoriously for a period of three months or more following taking possession of a unit, harbors or has harbored a household pet or pets, the harboring of which is not prohibited by the multiple dwelling law, the housing maintenance or the health codes of the city of New York or any other applicable law, and the owner or his or her agent has knowledge of this fact, and such owner fails within this three month period to commence a summary proceeding or action to enforce a lease provision prohibiting the keeping of such household pets, such lease provision shall be deemed waived.

c. It shall be unlawful for an owner or his or her agent, by express terms or otherwise, to restrict a tenant's rights as provided in this section. Any such restriction shall be unenforceable and deemed void as against public policy.

d. The waiver provision of this section shall not apply where the harboring of a household pet causes damage to the subject premise, creates a nuisance or interferes substantially with the health, safety or welfare of other tenants or occupants of the same or adjacent building or structure.

e. The New York city housing authority shall be exempt from the provisions of this section.”

TV4 "No Pet" New York Times Article

Статья Из Газеты "Репортёр"