coop shareholders with additional occupants

My sister and I are coop shareholders in same building. She has taken in an additional occupant, her "boyfriend", who unlike me doesn't work, stays home all day, and thus seems to have acquired a force in the building where he is in power and control over me.
The building is not entirely coop. There are tenants renting apartments in the building as well.
I feel that I have lost my respect as a paying shareholder in the building to him even though I have more shares in the coop than my sister.
How, if at all, can I have him evicted?
My sister doesn't feel as I do about evicting him.
My concern is aggravated by the fact that my sister's neighbor says he has people constantly in & out of the apartment & believes he is even selling drugs.
I followed him into the street the other day and found him getting into another person's parked vehicle in front of our building and saw them exchanging cash in the car.
Help!!!

[msgny]

Unless you can prove drug charges it will be hard for you to have any say or other persons in her apt??