Republican front-runner Donald Trump’s position on how to stop the drug epidemic is fairly simple—just say wall.

Trump wants to build a wall along the southern border of the United States, a “great wall that will keep illegal immigrants out.” But this Great Wall will, according to Trump, solve other problems. It will also keep drugs out of New Hampshire. In fact, Trump declares that when he builds his wall “no drugs are coming in.”

Why hasn’t anyone thought of this before? Wait, someone has, a group of fellows working for Richard Nixon, and they called it Operation Intercept. Douglas Valentine tells the story of this epic failure in his history of the DEA, The Strength of the Pack.

Nixon promised to solve the drug problem in a 1968 presidential campaign speech. He gave the speech to Martin Pollner, an advisor on crime, and told him to make it happen. Pollner was eventually assigned to work for Eugene Rossides, a Treasury Department official, supervising law enforcement with close ties to Myles Ambrose, the director of the Customs Service, which was then fighting a bureaucratic turf war with the Bureau of Narcotics and Dangerous Drugs (the predecessor of the modern DEA).

Pollner and Rossides wrote a paper, Ambrose took it to the White House and Nixon advisor John Ehrlichman assigned the problem to his hippie-hating assistant Egil “Bud” Krogh, who figured out that the relationship between drugs and crime made this a great political issue to exploit. So, Krogh became the chief White House advisor on drug policy, and in the summer of 1969, he put together