I always told myself I would never veto anyone because I found it unethical. However, my experience in polyamory lead me down a road where I "had to".
I say that in quotations because I truely felt I had no other choice in protecting myself, but I was very selective with the way I laid it out for my, now, exhusband. The key here is "exhusband".
I vetoed this specific person for a variety of reasons. She had already been involved with my husband for about 3 years. And her activity in our life had not only become the turbulent center of everything, she was completely derailing my life in so many ways unhealthy ways. It became absolutely absurd.
1.)My exhusband spent tens of thousands of dollars showering her with trips and attempting to keep her family out of debt. And she was planning on spending more even though I told her we could not afford it and asked her to please focus on other things besides spending endless amounts of money on luxury for herself. My protests were ignored and I was, in fact, told it was none of my business. I'm still paying our tax debt because of the reckless financial behavior and them refusing to heed my warnings.
2.) I watched her jerk around and manipulate her partners back and forth, over and over again, always causing drama centered around herself. Going as far as not only telling different parties different versions of the same story to victimize herself, but also confessing her lack of attraction to her second husband (and primary) and talks of running away with my, now, exhusband.
3.) She tore me down relentlessly back and forth, feeding me with hot and cold treatment. One second trying to get me in bed, and the next writing me out of a BDSM contract between she and my husband as well as trash talking me and my mental health right after dealing with my closest cousin committing suicide. In fact, she blamed my existential depression on the fact that I had been "mean" to her and that was why my guys didnt want to be close to me (I guess she ignored the 'existential' part of that). When I rejected her explanation as irrelevant, she lashed out badly and began lying to her whole family about me, leading them to ban me from seeing the kids at all.
Ultimately, this led to my veto. And ultimately it didnt work. It boiled down to protecting myself. I told my now ex that it was something I would not budge on. She is to be out of my life. He admitted at several points that she had a hold on him, even though he agreed and actively trashed her as being manipulative and abusive. There was a time where we seemed to be on the same page. Therefore if he chose to stay friends with her at any capacity, I would end the relationship. Period.
That being said, My relationship with my ex had alot of other faults. This was my reaching my breaking point with his lack of consideration and respect towards me.
To me, vetoes can signify one of two things.
A.) There is some sort of insecurity being protected. Which is totally normal, but IMO that is part of the journey of poly. Such insecurities should be examined and understood. When finding myself feeling such things in a poly relationship, I've actually learned alot about myself and its helped me become closer to the person I want to be.
Or B.) There is a trust issue within the relationship. If the person you are vetoing causes some sort of danger to yourself, your life, or your mental health, it shouldnt even require much discussion. And if this is the case, it's likely that your relationship should be reexamined. Who wants to be with a partner that allows their loved one to feel in danger?
Either way, vetoes should be closely examined and you really have to be honest with yourself about why one is being placed or why you want one.
My situation ended up being B and we are now divorced. Not only that, but hes back with this person as well as with the entire group of people he trash talked for a while. But let me tell you this, I most definitely am glad not to be married to a person like that anymore.