Nor did I realize you were allowing them passage to do so....
Minas Leon isn't covered by any treaty. Tara can operate only in a defensive capacity. Unless, of course, Ottar wants to attack and make many things very complicated for both himself and I.
EDIT: I mean, if I said no just because of the proximity to MI, it'd be like saying Tara can't go through Coria to reach the CE because it's too close to Eston.