Yeah, that’s INTERstate travel, but the 1st permits one to go and come as they please INTRAstate, does it not?
I don’t think it’s exactly unknown for police in the U.S. to ‘request’ things that they know they can’t actually legally demand, while making it sound just like an order.
(“I’m just going to look in your trunk now.”)
[Not that I think there are really many non-fictional detectives telling people not to leave town, but I don’t think the fact that it’s legally unenforcable would necessarily stop them]
On TV shows, after the detective tells the suspect “Don’t leave town”, the other detective nearly always says “You know we can’t do anything about that.” And the first detective usually responds “I know that, you know that, but the suspect doesn’t know that.”
More on the P&I Clause and the right to travel: Privileges and Immunities Clause - Wikipedia
Not that I’ve ever heard, at least in Ohio. A subpoena can be issued to you no matter where you go in the U.S., but in practical terms it’s often not worth the trouble to bring someone back from out of state unless it’s a very serious case and that person is a truly vital witness.