In the 1980s, not many people could plausibly claim stronger anti-drug credentials than Nancy Reagan. But Forest Tennant could.

"It's great for the Reagans to get up and say, 'Let's do something about the drug problem,' but I don't know who's going to do it," he told the Los Angeles Times in 1986.

"Only true professional people like myself can do very much with the drug problem."

The remark was characteristically haughty, but Tennant had the training, experience, and reputation to back it up. A physician and researcher with a doctorate in public health, he operated a chain of drug treatment clinics in California and was widely cited and consulted as an expert on drug abuse and addiction.

Tennant has published hundreds of scientific articles, testified in high-profile trials, and advised the NFL, NASCAR, the California Highway Patrol, the Food and Drug Administration, and the National Institute on Drug Abuse. The Times described him as "riding at the forefront of the current wave of anti-drug sentiment."

So when the folks at the Hoover Institution who produce the PBS show "Uncommon Knowledge" were looking for someone to debate drug policy with me, Tennant must have seemed like a natural choice. Imagine their surprise when he ended up agreeing that the war on drugs has been a disastrous mistake.

To be sure, Tennant is not completely comfortable with the idea of treating all psychoactive substances the way we treat alcohol. Among other things, he worries about underage access and legal liability issues.

But Tennant concedes that only a small percentage of drug users become addicted, that the drug laws are not very effective at preventing abuse, and that any increase in addiction that follows the repeal of prohibition is apt to be small. Equally important, he has come to realize after decades of dealing with addiction that the war on drugs imposes tremendous costs in exchange for its dubious benefits.

Tennant says the September 11 attacks had a big impact on his thinking about drug policy. He recognized that the connection between drugs and terrorism, cited by the government to justify the war on drugs, was actually a consequence of prohibition, which makes the drug trade a highly lucrative business and delivers it into the hands of criminals. "We've got to take the profit out of it," he says. Continued...