i cannot be too certain about any of this, but my understanding (and i might be totally wrong), is with respect to the positioning of the fence - is it in palestinian land ????? - or is part of it on palestinian land. if countries put fences, along their border, then i would think that is not a problem -and any country would be within their rights to do so.
anyway, if it stops bombings, then in a way, it could sort of be justified, but never the less, it might be better if the fence was entirely on israeli land