Originally Posted by SchrodingersCat
What really took me time to realize was this: Fairness is not about both partners having the same set of freedoms and boundaries. Fairness is each partner having access to the kinds of activities he or she is interested in, and respect of the other's personal boundaries.
I think this is very well put!
I have suggested a boundary in my relationship with my husband. I feel uncomfortable with the idea of him sleeping with or having a relationship with any of my closest friends. So I've asked him not to do that. This doesn't apply the other way around because he has a different approach to his friends and he wouldn't feel bad if I did something with them. However, everything's negotiable. If one day he came to me and said he has fallen in love with my best friend or that he has a very strong desire/attraction to her and asked if I could change my mind about the boundary, I probably would. For now it just means that I'd prefer if he didn't and if he could focus his attention to someone else, I would be pleased.
We also have some other boundaries, mostly related to safe sex practices. But if the new person was just tested (and could prove it) and someone you could trust (i.e. have known for a while already), then maybe some of the boundaries could be renegotiated.
I think that if I was "forbidden" to do something I wouldn't do anyway, I wouldn't even consider that much of a boundary for myself. For example if my husband said I couldn't eat meat from now on, I might be upset thinking that he thinks he can control me - but in the end it wouldn't change anything since I'm already a vegetarian and wouldn't eat meat anyway.