In the scene with the BA hunters, they come up with three theories to beat the Oath Rod.

I think we'll never know for sure if Mesaana used one of those, a variation of one of those, or a fourth idea (which is a very RJ-ilke way to solve this... I didn't like to give us some types of answer, when the characters themselves were in a position were they'd never know... He did that often, most famously with Asmodean). The idea of that scene seeems to have been to demonstrate the "binding process" wasn't as full proof as AS who don't try to find security holes might think. My guess is that Mesaana merely exploited the lack of security measures. She probably knew how this was done in the AOL to make sure there was no security gap and the binding really took place and for the right oaths. She knew the AS didn't even know this, so the loopholes in the oath taking were painfully obvious to her.

IMO, letting the person who swears channel the thread of spirit isn't the "normal" way to use a Binder. It works and all, but this means they can also weave other inverted weaves at the same time etc. This doesn't make much sense, when dealing with dangerous criminals like Semirhage.... if one of them get suicidal... nothing would prevent the from going in a killing spree, waving something nasty, even balefire until someone in the room killed them... I think in AOL sentencing, the criminal was probably shielded when taking the oath(s), and the Binder powered some other way, by the judge, or an official from the Guild or even the Standing Flows. The Aes Sedai let the person who binds herself to the Tower channel the thread, in part for the symbolism behind this gesture : you are willingly taking these oaths, no one but yourself bind you to them, you use your own power to do it etc.