As former Homeland Security Secretary Janet Napolitano pointed out, if you build a 50-foot wall, you'll soon be confronted with a 51-foot ladder. You need a strategy that involves layered defense: deployed patrols, sophisticated sensor equipment, and surveillance from the air. That is what has had a positive impact over the last generation.

We must recognize that this massive economic bloc that's emerging in North America cannot be accomplished unilaterally. It must be accomplished in partnership with Mexico and Canada. And we have to work together to secure the continent in order to keep dangerous people and dangerous things out and strengthen perimeter security on a continental basis.

We need to realize that the economic situation between Mexico and the United States is not just one in which we trade with one another. We make things together. We have shared production platforms. Cross-border trade is part of a single production process, and while apparently the Trump administration will seek to re-examine elements of that production platform, it is what it is and won't be easily dismantled.

Walls and barriers alone are insufficient to insure security.

We have to remember that information sharing is restricted by legal barriers and cultural barriers and by the notion that information is power and therefore should be hoarded so if you share information you can extract something in exchange. In today's digital online world, those who don't share information will be isolated and left behind. We need the data of other countries to connect the dots.

As former Homeland Security Secretary Janet Napolitano pointed out, if you build a 50-foot wall, you'll soon be confronted with a 51-foot ladder. You need a strategy that involves layered defense: deployed patrols, sophisticated sensor equipment, and surveillance from the air. That is what has had a positive impact over the last generation.

People should remember that Mexican migration is now at a net negative. More Mexicans are leaving through deportation and voluntary return than are entering the United States legally and illegally.