And borders are just imaginary lines. They are however a based around the underlying reality of geographical, cultural, and political factors. We could make a law that all airplanes must slow down to 50 miles per hour over crowed areas but that doesn't matter if most planes can't fly any slower than 120mph without falling out of the sky.

Laws do have to take into account things like physics and economics. The latter is the study of scarce resources that have alternative uses and specifically addresses things like the cost of labor and the affect of artificially manipulating it.