It's possible the Arcana would punish someone for trying to leave the relevant confines of the jaunt. Perhaps not likely, but it's not without precedent. So I'd prefer to test it myself, when I get a chance - I don't plan to ask someone else to take that risk.

[If they take it on themselves, he won't try to stop them either. That's their decision. But if someone is punished by the Trumps, it won't be on his behalf.]