https://www.ar15.com/forums/general/Does-the-US-already-own-an-easement-right-of-way-or-the-actual-of-land-along-the-nation-s-borders-/5-2044678/
Maybe they should threaten to build the wall 1500 yards inside the border and all those people stuck on the Mexico side can just travel to the nearest border crossing to enter the US side of the wall.