Who enforces HOA pet rules?

Our condo building has a rule that no dogs over 35 pounds are allowed in the building. One of the property owners in the building who owns several units uses a property management company. Recently when there was an animal complaint involving one of her properties, she instructed other property owners to not bother her, or her management company about the violation, but to call a state agency with the complaint. I am confused why it would not be the responsibility of the property owner to enforce the rules of her property.