However, fences alone will not prevent illegal immigration. Perhaps 35% to 40% of the illegal population entered the U.S. legally and simply never left. That is why border enforcement must be coupled with strict interior enforcement. We must create an effective entry and exit system that can track visa overstays and use a verification system, like E-Verify, to ensure that employers hire only legally authorized workers.

We must also create a robust guest worker program to match willing workers with employers according to flexible free-market forces. In 2006 and 2007, then-Sen. Barack Obama and other Democrats sided with the labor unions in an effort to water down such legislation. Reform will not go forward if the Democrats again resist the need to create a guest worker program.

At the same time, we must increase the number of visas and green cards available for high-skilled workers. We educate future business leaders and innovators from around the world at U.S. colleges and universities, and then force many who want to stay here to leave after graduation. Instead of creating jobs in the U.S., they return home or immigrate to other countries, where they become our competitors.

Finally, after the border is secure and our guest worker and visa programs are modernized, the legislation must address what to do with the people who are here illegally. I know some citizens want to round them all up, but this is not realistic. Instead, we can create an appropriate program to normalize their status.