Ah, yes, so it could be worded as, in grandiose treaty-lingo:
A. "If it should ever come to pass that Keplerstan is without any priest of Evilism among its nobles, war shall commence again with Evilstan."
But not as:
B. "Unless a Keplerian noble shall become a priest, war shall commence again with Evilstani."
In A, Keplerstan could reply, "None of our nobles desire to become a priest. We will abide by your treaty, but the priest must come from Evilstan."
If Evilstan has no priest to send either... then that's a horribly convoluted system. But if they have a priest and decline to send it, but go to war anyways over that clause of the treaty, then it is probably an IR violation (as they are clearly demanding a class change). But Evilstan could reply: "Okay, we'll send one of ours."
So Keplerstan will suffer some IC consequences for the IC decisions of its nobles to not become a priest (i.e. a spy from Evilstan among them), but were not at any point coerced, either individually or collectively, to make any class changes.
To clarify, the treaty could be stated formally as:
"Evilstan demands that there always be a priest of Evilism in Kepler. Evilstan is indifferent concerning how this should come to pass. Evilstan will accept a class-change of a Keplerian noble. Evilstan will accept the redeployment of one of its own priests. Evilstan will accept the immigration of a priest from a third-party realm to Keplerstan."
I would see that as perfectly fine.
