Apparently the Co-Op adopted a new house rule that requires "no new pet without prior approval policy". Well, the District Attorney got a new pet without prior approval. Yet, she thinks she should be able to keep the pet.
The District Attorney appears to be fighting the eviction by saying she only bought the Co-Op because it permitted pets, she wasn't properly notified about the new policy and that by allowing other inhabitants who had a pet prior to the policy to be grandfathered in without prior approval, the rule is improper.
Yet, the District Attorney should realize that when you purchase a Co-Op, you purchase an apartment subject to ever changing rules. If you don't like rules, get a house. While Co-Ops offer ease of living, it does not afford autonomy or privacy. Instead, its communal living with community rules.