This makes me rethink the whole border thing. We need motion sensors, observers and artillery.
Drones. A couple of dozen drones flying along the border with bombs that go boom.
Also, spray the border with a material or powder that can be tracked. Then you follow the tracks day and pick up the bandidos.
I'm going to revise my solution. Instead of 3 million "bouncing betty" land mines, up it to 20 million.
That will discourage them.