I do believe there are certain times where it's okay to ask this of them, but of course there is a line between asking out of respect for the relationship and asking/telling because you are possessive and distrustful of your partner.
There is someone that I have asked him not to speak to. He agreed. I guess I think it's okay because it wasn't an order or a command. If he wanted to speak to them he could have said no to me and done it. I would have no way to stop him not would I have attempted to do so. It was a request that he chose to accept, knowing he could say no if he wanted. I think it's okay as long as your partner isn't forced to do it, like if it's not an ultimatum like ignore them or I break up with you, that kind of thing.
If it's a tormentor from your past, and you know that it's just another window for drama, it's fair to say "please, don't get involved. All they're gonna do is say XYZ and start trouble."
That's a fair request. Your SO should respect that. Now, being possessive and insisting that your SO hide in the closet when your other other friends come over? That's wrong. Two different gals tried that crap on me, and I would only take so much of it.
Me for an example, I'm a jealous guy and I always tell which ever girl I'm speaking to that if she's going to speak to other guys then I will have to cut her off since I rather not deal with the jealousy.
Yes its acceptable sometimes, I remember I did when I saw that this female wasn't respecting our relationship and when she was drunk she'd call him and cry and sorts and she tried to insult me over the phone when I picked up etc. It was very dramatic.. usually I will tell them I would rather they NOT talk to someone if they disrespect my relationship but ultimately it's up to them to make that WISE choice lol.
I think it would only be acceptable in very extreme situations - for example, if you had been seriously assaulted by someone. Or if it was the case that the person you would not be happy for your partner to talk to was extremely manipulative, but I would still beware of making requests like this - it usually backfires pretty badly and creates distrust & discontent in what is otherwise a good relationship, as far as I have observed.
Other than that - why not let your partner come to his/her own conclusions about who they wish to talk to? I would find this type of request insulting to my intelligence and good judgement of people, and would most likely not feel like my partner thinks very highly of me and my capability to make those types of decisions for myself.
it's okay to ask them not to talk to a person if the person behaves hazardously like drinking and driving, drugs etc. It is not okay to ask them not to talk to a person out of jealousy if you have no proof that your SO is unfaithful. try to get to know your SO's friends. it really attractive if you can be open to associating with their friends and welcoming them as your own friends... unless their behavior is hazardous.