What's the correct resolution to this situation:

Letnav grants the Voting Concession promissory note to another player. The next turn Letnav uses Captain Lassir, forcing him to abstain from all future votes. The next turn the other player collects on the Voting Concession promissory note.

Does Letnav honor the note and get to vote with the other player, or must he abstain and the note is now null & void?

Without being able to check the exact wording I'd rule that said Promissory Note becomes obsolete as soon as the Lassir effect is activated.

A quite devious Letnev tactic come to think of it. Having an important vote swing your way with no risk of having to vote against your best interests in the future. Not sure if never being able to vote again is worth it though...