Where there's a wall there's a way.
Theresa Cardinal Brown writes in the May issue of Reason:
During a speech announcing his intention to seek the presidency, Donald Trump stumbled on what would become a signature issue for his campaign: Mexico. "When Mexico sends its people, they're not sending their best," he said. "They're sending people that have lots of problems, and they're bringing those problems with them. They're bringing drugs. They're bringing crime."
The "great, great wall" Trump wants to build isn't just aimed at stopping the people from crossing illegally into the United States; it's also supposed to stop the narcotics. But it isn't going to work.
To be blunt, the U.S. government is not likely to outspend the drug cartels at the border. Even if Trump is willing to put up the $21.6 billion the Department of Homeland Security estimates constructing a barrier would cost, the illegal drug trade is a $350 billion international business, according to the United Nations World Drug Program. A 2014 report from RAND Corp. estimated the American drug market for the four most prevalent illicit drugs—cannabis, heroin, cocaine, and methamphetamines—at $100 billion annually. The profit incentives to find ways over, under, around, or through any border infrastructure are high, and the cartels have more than enough money to spend on R&D.