Pshaw!
If this a "decades old" conspiracy, then why must the solution be done right meow? Why can't be sit down and figure out the right, and comprehensive, solution? Why have landmines so quickly been ruled out? That's a whole lot cheaper, and actually, I could get behind that... A big sign in Spanish, "Don't walk any farther, you will be blown up."
The Cartels will dig up the explosives, as will all the imported terrorists