I'm kind of curious why the down-votes so let me explain a bit further. Free trade isn't just about free movement of goods, it's also about free movement of labor. They're not the same thing but they are often lumped together, certainly for the purposes of Trump rhetoric and often in trade agreements.

One of Trump's signature campaign promises was to repeal NAFTA, which defines a class of skilled laborer status called TN status, which allows Canadians to show up at the border with $50, an offer letter and a diploma (in a skilled labor category) and work in the US. Mexican nationals are afforded similar status though require consular processing. This is cheap, flexible and un-capped. I'd wager the bulk of legal Canadians and Mexicans are in the US on TN status, so they would have to go were NAFTA repealed.

I have a hard time seeing a world where isolationist/protectionist policies increase free movement of labor so almost by definitions legal immigration will be restricted, IMO.