How can one person assur another from attending a shul? It's true that the madir has some rights to the shul as does everyone but what about the other person's chiyuv to daven with a minyan and hear keriyat haTorah? What if that's the only shul in town? It doesn't feel right. Any time someone gets mad at someone else he can forbid his chaver from attending shul and being part of tefilla b'tzibbur! Hayitachayn?
Sam Kosofsky
What would you say if someone owned an Esrog and refused to let others use it? Obviously the owner can refuse permission if he so chooses. This may not be the ideal thing to do but it is certainly within his rights as an owner of an article. Similarly, the partners in a Shul have a monetary ownership and as such have a right to restrict use of their property through a Neder if they so wish.
However, the Shach (YD 224:1) quotes the Ra'avad that there was a Takanah from the Geonim that the Isur does not take effect in the case of a Shul. This ruling is in fact brought in the Shulchan Aruch (OC 153:15). Rebbi Akiva Eiger quotes the Ma'amar Mordechai that this works because nowadays, due to the Takanah, the Shul does not belong to its congregants with respect to Nedarim that forbid its use to others.
Dov Freedman