Co-op board wants me to get rid of my puppy :(

Hello, looking for any advice.  I bought a co-op in Great Neck, NY, in
September 2002.  The person I bought it from owned a dog, and a
significant percentage of people in the building and other buildings
within the co-op also own dogs, and it was permitted to own a dog at
the time.  In February of this year a new rule was instituted that no
NEW dogs would be permitted as of February.  Apparently they were
supposed to put notices under people's doors to advise of this, but I
never got one.  A few weeks ago I bought a puppy for my fiance and
have been keeping him in the co-op.  A few days ago I received a
letter from the co-op manager that regarding the new rule and saying
that I would have to remove the dog immediately.  Any suggestions on
how to handle this?

Thanks!