Why should Congress cough up the money to build a border wall? President Trump claims it would help stop the flow of deadly drugs coming in from Mexico.

Historically, in terms of sheer weight, marijuana has been Mexico’s leading illicit drug export to the U.S. But last year, “the average Border Patrol agent was seizing just 25 pounds [of marijuana] for the entire year, or less than half a pound per week—a drop of 78 percent from 2013,” writes David Bier, a policy analyst at the Cato Institute, in the cover story of Reason’s April 2019 issue.

This trend has nothing to do with increased border security, or a crackdown on the Sinaloa Cartel and its former leader, Joaquín ‘El Chapo’ Guzmán, who was found guilty on 10 criminal counts in U.S. federal court last week. The falloff in pot smuggling, Bier argues, is a direct result of state-level legalization here in the U.S.

Reason’s Katherine Mangu-Ward sat down with Bier to discuss why easing pot prohibition is doing what the failed war on drugs never could.

Produced by Alexis Garcia. Camera by Austin Bragg and Todd Krainin.