It is controlling to dictate a partner's friendships.
John noticed that his girlfriend, Mary, hangs out with a lot of guy friends from work, which made him worried that she could leave him for one of them.
John wants to do anything to keep Mary as his girlfriend.
John sits down Mary and tells her about his jealous emotions, he doesn't ask her to stop seeing them, he just wants her to understand what he is feeling.
John tells Mary that he doesn't like her hanging out with a bunch of guys and tells her she can only have girl friends outside of work.
John and Mary attend counseling together, John eventually get's over his jealousy, and they end up getting married one day.
Mary decides that John is too controllers and ends their relationship.