He's got to get anything through congress, which was notably hard for most of Obama's ambitions, and will probably be hard for many of Trump's ideas, too. Surely if you have lived in a country for years, and have permission and citizenship, their would be huge public resistance to eviction. I mean, the whole of America is immigrants, except for the natives, obviously. How far back do you go? They could only apply any new rules to new arrivals, surely. Or people who haven't been there for years already. I would think so, anyway.