The issue is reducing demand. If we can reduce demand for the product in this case drugs, then we wouldn't need a wall to stop the flow of contraband into the US. Also a wall may be a great thing in the 1500's, however a wall does not stop today's problems. Ensuring domestic tranquility is only done when we have a population that is educated and informed. This is the reason the founding fathers put a stipulation of land ownership into voting. We need civics in our schools to understand why we have/need a government.