I recently listened to a Heritage Foundation podcast about the federal government's holding of vast amounts of land in the western US. [States of Dependence: Reducing Washington’s Control of the Western U.S., June 10, 2014] This being Heritage, they did not like the feds holding so much land. The podcast was not about immigration but the topic came up anyway. A staffer from Senator Hatch's office asked a question about the role of federal land holding in securing the southern border.
Rep. Rob Bishop (R-UT) who heads a committee overseeing federal land replied that big swaths of the southern border are in some kind of official wilderness status or otherwise in some protected status.
This means that Border Patrol agents are circumscribed by law in the methods of enforcement (e.g. they can't use vehicles). He said the only way to fix this was by statute.
It was interesting and something I never knew.
You can watch this exchange below at 40:30, or click here to go to min 40:30 in a new window.
James Fulford writes: I see that that Rob Bishop saying the same thing for years, but still nothing has been done about it, and I had actually forgotten it myself