The enforcement is the problem if it is not secure legally. If you want to handle it with an iron fist like a dictatorship sure you can create laws to that effect, but there should be some human values on the books that makes those laws humane.

Considering practically every concept has the concept of a temporary visas, it must not be that insane of a concept.

It's basically an objective fact at this point that excessive immigration is really, really bad, just look at all the politicians flipping sides on the issue. Look at the stats on European countries with the highest immigration rates vs those with the lowest (e.g. Poland)