The issue is not clear-cut, imo, because it is a threat that *another* *might* do something, and not an act on itself.
They may be very lenient on how many turns can be missed, and there's no way to know.
This same line of reasoning can be used to argue that it's OK for a duke to say "Don't go to the tournament or the judge will fine you". After all, it's just the duke that's talking, not the judge. The duke can't fine anyone. And the judge hasn't fined anyone. And no one has acted on the threat at all. And besides, they may be lenient on not fine anyone at all. So therefore it's OK, right?