It's Trump. It's definitely trolling, it could possibly be ignorance, at least to the extent of his powers, but it is certainly part of his "flood the zone" strategy. Now people will start yelling about how he lacks the power to do such a thing and fewer people will be yelling about the shit that matters.
He's probably the only person who truly cares about what O'Donnell says or does. Most people probably don't even know or remember that she left the country. She's done. She's a has been. He just needs to forget her.