There is no or a very small impact of regulation on the number of exiled people coming in country. However, making more people illegal let bosses exploit them more. Those workers could not sue their boss because of those regulations, and most conservative unions rely unfortunately too much on legal solutions.
So if a country couldn’t limit immigrations, it could exploit more people and bybass human right with regulations against exiled people.
Yes, this is only positive for far-right bosses, and awful for others. But guess who decide in a capitalist economy ?