It seems that Niva has had quite enough of the Transport Wing constantly having some excuse or another for why they can't work - particularly as the latest keeps them from betweening. More so, it seems that the proddy Weyrwoman has had enough of Istan bronzeriders causing her and the Weyr problems - distracting all the eligible (and in some cases, non-eligible) women of the Weyr. And so, there's been a decree that Istan Bronzeriders are banned from Xanadu until further notice.
Now, given that Niva does have a history of banishing and banning various people, parties, and groups at a moment's notice for some imagined slight or another, many people are assuming that once Kilaueth rises, everything will be forgotten. However, until then, it seems that visiting Istans are encouraged to claim a different home, or at the very least, stay out of the Weyrwoman's sight.