You can't build a wall on the border because 2/3 of the border is over the middle (more accurately, the thalweg[0]) of the Rio Grande and the Colorado River. So

You can't build a wall on the border because 2/3 of the border is over the middle (more accurately, the thalweg[0]) of the Rio Grande and the Colorado River. So you'd have to build it on the American side, most of which is private property that would have to be taken by eminent domain, and its owners compensated, many of whom would sue to prevent that – notably, Cards Against Humanity[1]. [0] https://en.wikipedia.org/wiki/Thalweg https://en.wikipedia.org/wiki/Thalweg [1] https://cardsagainsthumanitystopsthewall.com https://cardsagainsthumanitystopsthewall.com