Quote Originally Posted by Thorogood Roele
If he sees one harming another mage, he would be honor bound to ensure he's not doing so as an act of lawful warfare, commanded by his liege before toasting him. If he doesn't observe and actual ACT of violation, or have direct knowledge of a past transgression, he would have no reason to act against that mage, reguardless of whether he swore to the oath or not.
Except the not harming another mage only applies to those who have sworn the Oaths not those who abide by them. Even more situational things to work out in role-play.

That said, I believe it also says in Cities of the Sun, that they do hunt their own mages (khinasi) if they refuse to go take the oaths.
Yup that is why the paladin of Avani code of behaviour (from the revised ch 1 of the BRCS) talks about them often being used to hunt downthose transgressors.