And even then it will take a week for him to scratch out his signature.
He can still refuse to do it, to physically sign the order.
Then they'll have to remove him from the case, or maybe from his job entirely, which will take time, during which Flynn is silenced.
If they remove him from his job (by forcing him into emeritus status for instance) he will get a very cushy sinecure at Harvard or some other fancy school of his choice. I bet it's being arranged right now.
Flynn is no longer silent. He is on Parler and has been speaking out.